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 BEGINNING 
 FOSSIL HUNTERS 
 
 Charles W. Collinson 
 
 laiNOlS GEOLOGICAL 
 
 SURVEY LIBRARY 
 
 JUL 16 W* 
 
 9lUwib State Q&dcKfical Suaaj^ 
 
STATE 
 
 of ILLINOIS 
 
 William G. Stratton, Governor 
 
 DEPARTMENT of 
 REGISTRATION and EDUCATION 
 Vera M. Binks, Director 
 
 ILLINOIS STATE GEOLOGICAL SURVEY 
 
 3 3051 00004 7385 
 
 ILLINOIS STATE 
 GEOLOGICAL SURVEY 
 John C. Frye, Chief 
 URBANA, ILLINOIS 
 
 IJUKH — 5-56) 
 
GUIDE FOR 
 
 BEGINNING FOSSIL HUNTERS 
 
 Gkcvde& W. G&lUukm 
 
 9lL4AfricrfMm4- Wf Mgaa& Z. Irftewi 
 
 Printed by Authority of the sun- of Illinois 
 
GUIDE FOR 
 
 BEGINNING FOSSIL HUNTERS 
 
 Charles W. Collinson 
 
 v^BTOONG before your birth, long before your 
 fi/v/^ grandfather and grandmother were born, 
 g j%p : jeven before there were any men or the 
 r<fci ^Mississippi River existed, there were ani- 
 ViJ^r.7; v ^rnals on the earth. 
 
 You may ask, "If there were no men around to 
 see them, how do we know that there were animals 
 then?" 
 
 That question is pretty easy to answer, for the 
 animals left their marks behind and we call those 
 marks fossils. 
 
 Some fossils are just foot tracks or worm holes. 
 Others were made when mud sifted into empty 
 shells and slowly turned to stone. Many bones or 
 shells, even some skin and hair, have been pre- 
 served in the rocks for millions of years. 
 
 Of course the rocks in ^SSSGSZ 35^ 
 
 which the fossils are en- ^^*$WI/$ 
 
 cased weren't always rocks. 
 At one time the sediments were just mud or sand 
 on the floor of the sea; some were sand dunes on 
 an ancient land. As time passed the sediments were 
 buried under more sand or mud, and with the pass- 
 ing of more time the sand and mud became rock. 
 
The fossils in the rocks, however, are only a 
 small part of all the life that has existed on our 
 planet. For every fossil we see, millions of ani- 
 mals and plants have lived, died, and been destroyed 
 without leaving a trace. However, by carefully col- 
 lecting fossils and recording the layers of rocks 
 they came from, we can reconstruct hundreds of 
 generations that have lived on earth at one time or 
 another since the beginning. 
 
 Finding and collecting fossils not only helps to 
 write missing chapters of earth history but is also 
 an exciting adventure. It is an animal hunt - a hunt 
 for creatures often more strange than any living on 
 earth today. 
 
 Your first fossil discovery will be a thrill. Later 
 you will find that a search through a quarry or a 
 strip mine is an excursion to an ancient seashore 
 or a plunge to the bottom of a long -vanished sea. 
 
 You also step into the past when you climb the 
 loess bluffs along our large rivers. You return to 
 the days when a great glacier invaded Illinois and 
 the rivers from the melting ice ran milky with rock 
 flour ground up beneath the scouring ice. 
 
 After the rock flour had settled and dried on the 
 river floodplains, it was swept aloft by the winds. 
 Huge dust storms swirling over the bluff s and near- 
 by uplands deposited the rock dust, called loess. 
 Snail shells were preserved in the loess but, except 
 for an occasional bone or tooth of a mammoth, most 
 of the plant and animal remains have disappeared. 
 
 In addition to outdoor adventure, a successful 
 hunt provides interesting trophies for your collec- 
 tions. Many of science's most valuable fossil finds 
 have been brought in by amateur hunters. 
 
WHAT ARE FOSSILS? 
 
 A fossil is some evidence of a prehistoric ani- 
 mal or plant, preserved in rock, that gives a clue 
 to the characteristics of the organism. The remains 
 of animals or plants that lived during historic time 
 are not considered fossils. 
 
 The oldest fossils in Illinois are found in rocks 
 such as sandstone, limestone, or shale. Some are 
 only impressions of the outside of a shell; some 
 are fillings of the inside. 
 
 Parts of the original shell may be preserved, but 
 in many fossils the hard parts of the animal have 
 been replaced by a material different from that of 
 the original. Silica and calcium carbonate, which 
 are easily preserved, commonly replace the ori- 
 ginal shell material. 
 
 Some fossils were made by marine worms which 
 burrowed in the sand or mud of the sea floor. The 
 worms themselves are rarely found as fossils but 
 their trails and holes are common. The burrows 
 and holes are fossils just as much as the animals 
 themselves would be if they had been preserved. 
 
 In many places in Illinois, shells of clams, snails, 
 and brachiopods are preserved with little change 
 and are much as they were the day they were buried 
 on the floor of a now-vanished sea. 
 
 The plant-fossil materials that make up the coal 
 beds of Illinois are the remains of primitive trees 
 and plants that lived in swamps during the Coal Age. 
 When the plants died they fell into the water and 
 were preserved as peat that later became coal. 
 
 Many fine fossils found in the coal and overlying 
 shales represent the roots, trunks, and leaves of 
 the plants. A few of the insects that lived in the 
 trees also are preserved. 
 
Among the youngest fossils found in Illinois are 
 the teeth and bones of bison, giant beavers, deer, 
 and elephant-like animals called mammoths and 
 mastodons, which lived during the Ice Age. Com- 
 plete skeletons of the animals are rare, but teeth 
 and tusks are on exhibit in many museums. 
 
 L-^»W& 
 
 Woolly Mammoth 
 (After drawing by Charles R. Knight) 
 
 WHERE TO LOOK FOR FOSSILS 
 
 1. Quarries are excellent places to find fossils 
 because so much rock is exposed. Old abandoned 
 quarries are best for collecting because the rocks 
 have been weathered for several years and the fos- 
 sils generally stand out in relief. 
 
 If you plan to collect in a quarry, be sure to get 
 permission to enter it. In that way someone will 
 know where you are in case of accident. In active 
 quarries there is danger from falling rock during 
 blasting. If the quarryman doesn't know you are in 
 the quarry, he cannot warn you when he is going to 
 set off a blast. 
 
2. Some of the best collecting sites in Illinois 
 are in the cliffs and bluffs along our major rivers, 
 the Mississippi, Illinois, Ohio, Wabash, and their 
 tributaries. At these places whole fossils are often 
 weathered out and may be picked up easily. 
 
 3. Well-known collecting sites for plant fossils 
 are the coal strip mines of Illinois. Perhaps the 
 most famous is the Mazon Creek area near Braid- 
 wood in northeastern Illinois which has supplied 
 beautifully preserved impressions of ferns, tree 
 leaves, and a few insects to museums throughout 
 the world. Many strip mines also yield fine brach- 
 iopods, snails, clams, and cephalopods. 
 
 4. Highway cuts through bedrock commonly ex- 
 pose beds containing fossils. Be careful along road 
 cuts, especially if there is heavy traffic. 
 
 5. Ice Age fossils, such as mammoth and mas- 
 todon teeth and tusks, have been found mostly in 
 gravel pits but also in foundation excavations and 
 ditches in all parts of the State. 
 
 6. Most of Illinois' major rivers have banks of 
 wind-blown glacial dust called "loess." The shells 
 of air-breathing snails which lived during the Ice 
 Age are common in the loess. 
 
 7. Actuallyyou canfind fossils almost anywhere, 
 in the gravel or crushed stone of your driveway or 
 in stone walls and foundations. You may see fossils 
 in many places where you can't collect them, such 
 as counter tops in restaurants, utility marble in 
 public buildings, in stone sidewalks in several of 
 our older cities, or in riprap along the shores of 
 Lake Michigan and our major rivers. 
 
TOOLS FOR COLLECTING FOSSILS 
 
 1. Hammer - a bricklayer's hammer will work 
 well. 
 
 2. One or two cold chisels, preferably one large 
 and one small. 
 
 3. Knapsack or basket in which to carry your 
 fossils. 
 
 4. Old newspapers or a roll of tissue paper for 
 protecting fragile specimens. 
 
 5. Magnifying glass or hand lens, 3 to 10 power. 
 
 6. Pencils and paper for labeling the specimens. 
 Much of the value of a particular fossil lies in know- 
 ing where it was found and the bed it came from. It 
 is important to keep records of your collecting. 
 
 TIPS ON COLLECTING FOSSILS 
 
 1. When you look for specimens in a quarry or 
 on a shale slope, sit down or get on your hands and 
 knees and look carefully. Spend some time in one 
 spot before you move on to another. Excellent fos- 
 sils have be en found in places that others had passed 
 over many times. 
 
 2. If you find a good fossil embedded in rock and 
 you are not certain that you can get it out without 
 breaking or destroying it, don't spoil the fossil. If 
 you leave it, the wind and weather may help loosen 
 the fossil from the rock by your next visit. 
 
 8 
 
SOa 
 
 3. If you do decide to chisel a fossil from the 
 rock, be patient and take your time. If possible, 
 chisel a narrow trough around the fossil, taking 
 care always to point the chisel away from the spe- 
 cimen. When the trough is as deep as the fossil, or 
 deeper, strike the base of the pillar you have made 
 and the fossil should pop out. 
 
 4. Where the rock is very fossiliferous, it may 
 pay you to take small blocks of rock and break them 
 into pieces with your hammer. In the process the 
 rock tends to break around the fossils. If there are 
 enough fossils in the rock, you probably will get 
 some unbroken specimens. 
 
FORAMINIFERA 
 
 Hyperammina 
 40 X 
 
 Involutina 40 X 
 
 Bathysiphon 
 
 Thurammina 40 X 
 
 Schwagerina 6 X 
 
 SPONGES 
 
 Plcdef 
 
COMMON TYPES OF ILLINOIS FOSSILS 
 
 FORAMINIFERA (for-am-i-nif-er-ah, plate 1). 
 Foraminifera are very small one -celled animals, 
 commonly called "forams 
 They are important to 
 geologists, who use 
 them to identify oil- 
 bearing rocks. 
 
 _,, , ..- , Fusilina A Foraminifer 
 
 They are beautiful- .. ... , ._ 4 . Iin v , 
 
 3 Magnified 10 times (10 X) 
 
 ly shaped little shells, 
 
 but you will be able to see them clearly only with 
 a magnifying glass or hand lens. Some are calcium 
 carbonate, others are made of tiny sand grains ce- 
 mented together with silica. 
 
 Some foraminifera make their shells of parts 
 that come from the skeletons of other animals. 
 Some kinds are so particular about the kind of 
 materials they use that they select only grains of 
 a certain color and size. 
 
 Foraminifera live in tremendous numbers in the 
 seas today. They lived as far back as the Ordovician 
 period, more than 400 million years ago (see the 
 Geologic Time Chart, page 2). 
 
 Calcareous foraminifera such as Endothyra (en- 
 doh-thy-rah, plate 1) are very abundant in Illinois 
 in the Salem limestone, which occurs in the bluffs 
 of the Mississippi River near the end of Mc Adams 
 highway northwest of Alton and in the bluff s of Mon- 
 roe and Randolph counties. The Salem limestone 
 also crops out near Anna and Jonesboro in southern 
 Illinois. 
 
 Another kind of calcareous foraminifer, Fusilina 
 (few-sil-eye-nah), is very common in rocks of 
 Pennsylvanian age throughout Illinois. The little 
 
fossils look like grains of wheat and are so abun- 
 dant in some limestones and shales that they can be 
 collected by the thousands. 
 
 For a list of localities where foraminifera are 
 abundant, see pages 162-167 of Illinois Geological 
 Survey Bulletin 67. 
 
 SPONGES (plate 1). Sponges are mainly marine 
 animals that live attached to the sea floor. Fossil 
 sponges are 
 numerous in 
 some parts 
 of Illinois. 
 They are not 
 the flexible 
 sponges you 
 and I know, 
 of course. 
 Instead they 
 have a hard 
 skeleton of 
 calcium car- 
 bonate or 
 silica. The 
 
 oldest ones are known from Cambrian rocks and 
 are about 550 million years old. 
 
 One fossil sponge, called the "sunflower coral," 
 is common in the Ordovician rocks of north -central 
 and northwestern Illinois. 
 
 Another, called Hindi a , is found in Silurian rocks 
 exposed in quarries in the Chicago region. It looks 
 like a small round ball but, when broken, is seen to 
 be made of thousands of radiating rods of calcium 
 carbonate. 
 
 Modern Sponges 
 
 12 
 
u 
 
 .:W- -£'.•;■ '\ ft F i?± K 
 
 Modern Corals 
 
 CORALS (plate 2). Corals are small brightly 
 colored marine animals that look much like flow- 
 ers. The animal 
 grows an external 
 stony skeleton 
 connected with 
 radial partitions 
 on the inside 
 which divide the 
 body into cham- 
 bers. The animal 
 itself is called a 
 polyp and the 
 skeleton is called 
 coral. 
 
 Some corals 
 live together in 
 colonies made up of 
 hundreds of individuals, 
 
 attached to each other by their outer skeletal walls. 
 They sometimes form coral reefs hundreds of miles 
 long. 
 
 The skeletons of solitary polyps maybe cushion-, 
 horn-, or tube -shaped, each with a depression in the 
 top in which the animal lived. The solitary corals 
 are referred to as horn or cup corals. 
 
 In colonial forms the skeletons may be either 
 branching or closely packed and massive. Corals 
 live only where the seas are warm and shallow. 
 They are very numerous in today's tropical seas. 
 The animals have been common throughout geolo- 
 gic timesothat it is easy to collectfine specimens. 
 
 Fossil corals are most common in limestone, 
 where they sometimes make up a large part of the 
 rock, but they also are found in shale and sand- 
 stone. 
 
 13 
 
BRYOZOA 
 
 Lioclema 6X 
 
 Stomatopora 18 X 
 
 CORALS 
 
 Streptelasma 2 /3 x 
 
 Lithostrotionella 1/2 X 
 
 Plate 2 
 
 Lophophyllum I X 
 
BRYOZOA (bri-o-zoh-ah, plate 2). The tiny col- 
 onial animals called bryozoa generally build stony 
 skeletons of calcium carbonate. 
 
 
 Archimedes 
 A Mississippian Bryozoan 
 The fronds are commonly called Fenestefla. 
 
 They grow in a variety of shapes and patterns, 
 mound-shaped, lacy, tree-shaped, or even screw- 
 shaped. Each skeleton has numerous tiny holes, 
 each of which is the home of a minute animal. They 
 live attached to the sea floor, to stones, or to other 
 animals. 
 
 Bryozoa are very common as fossils. The oldest 
 ones come from Cambrian rocks about 500 million 
 years old, and their descendants live today. 
 
 During the Mississippian period bryozoa were 
 so common that their broken skeletons formed en- 
 tire limestone beds. Fossil bryozoa may be found 
 either in shales or limestones and they occur 
 throughout Illinois. 
 
 15 
 
BRACHIOPODS 
 
 Lepidocyclus 2/3 X 
 
 Rhynchotreta IX 
 
 Pkh3 
 
 Paraspirifer 2/3 X 
 
Herbertella 1/2 X 
 
 Leptaena I X 
 
 Plate 4 
 
 Platystrophia 2/3 x 
 
Mississippian Brachiopods 
 
 BRACHIOPODS (brack-e-o-pods, plates 3 and 4). 
 Brachiopods are marine animals that have two 
 shells, an upper one 
 and a lower one. The 
 right and left halves 
 of each shell are mir- 
 ror images but the two 
 shells are not exact- 
 ly alike. The shells 
 may be of lime, phos- 
 phate, or a horny sub- 
 stance, and they range 
 in size from less than 
 1/4 inch to several 
 inches. 
 
 Most brachiopods live attached to the seafloor by 
 a fleshy stalk that is an extension of the soft body. 
 Some forms lose the stalk when they become adults 
 and either attach themselves directly to the sea 
 floor or lie loose in the mud or sand. Some have 
 spines that serve as anchors. 
 
 Brachiopods are not common in most oceans 
 today, but at times in the past they were the most 
 abundant shellfish and sometimes formed large 
 shell banks much as oysters do today. 
 
 The oldest fossil brachiopods are found in Cam- 
 brian rocks which are about 550 million years old. 
 However, the animals became abundant in Ordovi- 
 cian time and remained so throughout the Paleozo- 
 ic era. 
 
 In Illinois, the fossils are especially common and 
 well preserved in the Mississippian limestone and 
 shales of the Ohio. and Mississippi river bluffs, but 
 you can find them easily in almost any part of the 
 State. 
 
 18 
 
Marine Worm Jaw 
 (Greatly magnified) 
 
 MARINE WORM JAWS (plate 5). Marine worm 
 jaws are easily preserved and are known in nearly 
 
 every geologic system. Most of 
 them are composed of chitin (fin- 
 gernail material). They are black 
 and shiny and have many teeth. 
 Sea worms live today and the fos- 
 sil record of worm trails goes 
 back to the pre -Cambrian period. The oldest worm 
 jaws are found inOrdovician rocks. They are com- 
 mon in the Silurian rocks of northeastern Illinois. 
 
 GASTROPODS (gas-troh-pods, plate 5). Gastro- 
 pods commonly are called snails. The snail carries 
 its shell on its back and retreats into it whenever 
 danger threatens. As a snail grows larger it expands 
 and lengthens the 
 shell. Most com- 
 monly the shell 
 is coiled in a 
 spiral, but some 
 are shaped like 
 a Chinese coolie 
 hat. 
 
 There are many 
 kinds of gastro- 
 pods. Some live 
 in the sea, some :j3 * 
 live in rivers,'-.-/ ^^ 
 and still others -^Msfig^ 
 live on land. The Modern Marine Gastropods 
 
 ones that live in water have gills like fish, but those 
 thatbreathe air have simple lungs. Gastropods have 
 a distinct head, feelers, eyes, and a mouth. Some 
 have a rasp-like tongue. The snail uses its tongue 
 for boring into other shellfish which it eats. 
 
 19 
 
WORM JAWS 
 
 Lumbriconereites 10 X 
 
 lldraites 20 X 
 
 Arabellites 20 X 
 
 GASTROPODS 
 
 Oenonites 10 X 
 
 Trochonema IX 
 
 Bellerophon IX 
 
 PlateS 
 
Snails are common as fossils in the Ordovician 
 and Pennsylvanian rocks of Illinois. Snails that 
 lived during the Ice Age are abundant in the loess 
 in places along the bluffs of the major rivers and 
 may be recovered by washing the loess through a 
 coarse screen. 
 
 The oldest snails lived during the Cambrian pe- 
 riod, more than 550 million years ago. 
 
 Straight Ordovician Cephalopod 
 
 CEPHALOPODS (sef-a-lo-pods, plate 6). Ceph- 
 alopods have beenfound as fossils in rocks of many 
 ages, and many are alive today. Squids, octopuses, 
 cuttlefish, and the pearly nautilus are among the 
 cephalopods presently living in the seas. 
 
 Cephalopods are the most advanced of all animals 
 without backbones. They have a highly developed 
 nervous system with eyes much like human eyes. 
 
 The cephalopod 1 s mouth is surrounded by long 
 tentacles commonly armed with suckers. Beneath 
 the tentacles is a tube through which the animal 
 can force a jet of water and thus move about by 
 jet propulsion. 
 
CEPHALOPODS 
 
 , ,. ., 9/ v Endolobus 2/ 3 x 
 
 Lechntrochoceras *■/■$ X 
 
 Plate 6 
 
 Imitoceras 2/3 X 
 
Coiled cephalopods live today only in the South 
 Pacific but in the geologic past they were scattered 
 throughout the world. Modern squids live in shal- 
 low coastal waters over much of the globe. 
 
 Most of the ceph- 
 
 i A** 
 
 
 alopods we find as 
 fossils had a calcar 
 eous outer shell. 
 Some were loosely 
 coiled, some tightly 
 coiled, and others 
 shaped like a 
 tapered tube. 
 
 As the shelled ==== 
 forms grew, they *—# 
 periodically made 
 new and larger shell Modern Co,led Cephalopod 
 chambers to fit their bodies and sealed off the old 
 part of their shells with a wall of pearly calcareous 
 material - hence the name, "chambered nautilus." 
 
 During the Ordovician period, about 450 million 
 years ago, some straight cephalopods grew to be 
 as long as 19 feet, although most were much short- 
 er. Straight cephalopods were common in Ordovi- 
 cian and Silurian time; coiled ones became fairly 
 common only by Later Paleozoic times. We find 
 both in the Pennsylvanian rocks of Illinois. 
 
 PELECYPODS (pe-les-i-pods, plate 7). Pelecy- 
 pods include oysters, clams, mussels, and cockles. 
 They have been found in the oldest marine rocks 
 known and still are very numerous in the seas and 
 rivers today. Many of our pearl buttons are made 
 from Mississippi River clam shells. 
 
 23 
 
PELECYPODS 
 
 Myalina 2/3 x 
 
 Clionychia 2 /3* 
 
 Plata 7 
 
 Aviculopecten 2/3 * 
 
Most pelecypods have two shells which are mir- 
 ror images of each other, one on the right and one 
 on the left. Each shell has a beak that points for- 
 ward and represents the spot where the shell be- 
 gan to grow. The top edge of each shell commonly 
 has several teeth and sockets that fit into those of 
 the opposite shell to make a hinge. The outside of 
 the shell generally is ornamented by ribs, spines, 
 and growth lines. 
 
 :: : ^^ 
 
 Pecten 
 A Modern Pelecypod 
 
 Most pelecypods form shell banks in the seas or 
 rivers, on sand and mud flats. Many burrow into the 
 mud or sand, and even into wood or rock. Some oy- 
 sters attach themselves to rocks and others creep 
 about the sea floor by means of a hatchet-shaped 
 foot thrust between the open valves. A few (scallops) 
 move by jet propulsion, opening the two valves slow- 
 ly and snapping them shut to force the water out in 
 a jet stream. 
 
 Fossil clams are common in some Pennsylvanian 
 rock formations in central Illinois and in some Or- 
 dovician limestones in northern and western Illinois. 
 
 25 
 
OSTRACODES 
 
 Dalmanites V2* 
 
 Isoflus l/ 3 X 
 
 Plate! 
 
TRILOBITES (try-lo-bites, plate 8). Trilobites 
 have been extinct for more than 200 million years. 
 They often are pre- 
 served ingreat de- 
 tail and are prized 
 as fossils. Two 
 grooves extending 
 down the back of 
 the animal divide 
 it into three lobes, 
 hence the name 
 "trilobite." 
 
 Trilobites had a 
 
 Ordovician Trilobite 
 
 head with eyes and a mouth, a jointed body, and a 
 tail. The animals were cousins of the crabs and 
 lobsters and lived in the sea. 
 
 They were covered with a horny armor, jointed 
 so the animal could move. Trilobites shed their 
 armor much as snakes shed their skins, so each 
 animal could have provided several fossils. 
 
 Trilobites were abundant in Cambrian, Ordovi- 
 cian, and Silurian times and were among the most 
 important animals then on earth. They became ex- 
 tinct during Permian time. 
 
 OSTRACODES (os-trah-cods, plate 3). Ostra- 
 codes are very small animals which are common 
 as fossils but are rarely large enough to be seen 
 by the naked eye. 
 
 They have been present on earth since the early 
 part of the Ordovician period, and occur today in 
 great numbers in lakes, rivers, and seas. Ostra- 
 codes prefer shallow water and live in vast hordes, 
 crawling over the bottom or swimming near the 
 surface. 
 
 They have two shells, one on each side of the 
 body, so that some ostracodes look much like small 
 
 27 
 
GRAPTOLITES 
 
 CYSTOIDS 
 
 
 Tetragraptus I X 
 
 Caryocrmites IX 
 Dendrograptus 40 X „ o/ocys „ 7es y^ BLASTOIDS 
 
 Pisocrinus IX 
 
 Crinoid Columnals IX 
 
 Pentremites 2/ 3 X 
 
 AU? <? 
 
Ordovician Crinoid 
 
 clams. But the animal inside looks much like a 
 shrimp or an insect with jointed legs and feelers. 
 As the animal grows, it sheds its shells and forms 
 a new pair. The shells maybe smooth or ornament- 
 ed with pits, bumps, ribs, or spines 
 
 CRINOIDS (cry^noids, 
 plate 9). Crinoids 
 are called "sea 
 lilies," but they 
 are animals ra- 
 ther than plants. 
 
 They look like 
 plants, however, 
 because the body 
 skeleton or calyx 
 generally is on 
 the end of a stem 
 made of button - 
 like discs and held on the sea floor either by a stony 
 anchor or root-like arms. The mouth, on top of the 
 body, is surrounded by arms which sweep food into 
 the mouth. The body is made of calcareous plates 
 which fit together like irregular bricks. 
 
 When the animal dies, the plates and discs tend 
 to fall apart and sink to the sea floor. Many of the 
 limestone beds in Illinois are composed mostly of 
 crinoid plates and discs. 
 
 The complete calyx is a highly prized fossil. Good 
 ones are found in the limestone cliffs along the Mis- 
 sissippi River between Burlington and Alton. 
 
 Stems or stemdiscs are common throughout most 
 of Illinois and popularly are called "Indian beads" 
 or "fish bones." The oldest crinoids come from Or- 
 dovician rocks. Some crinoids live today, mainly 
 in deep parts of the ocean, but they are not nearly 
 so common as in the past. 
 
 29 
 
BLASTOIDS (blas-toyds, plate 9). Blastoid fos- 
 sils commonly are called "sea buds." They are 
 closely related to crinoids but differ from crinoids 
 in that instead of arms they had small hair -like 
 pinnules which swept food into the mouth. The soft 
 pinnules rarely were preserved. 
 
 Some blastoids had stems but others did not and 
 were attached directly to the sea floor. Like cri- 
 noids, they had a mouth at the top of the body (calyx) 
 surrounded by small round holes that conducted 
 water into the body. 
 
 The oldest blastoids, found in Ordovician rocks, 
 lived about 450 million years ago. The animals sur- 
 vived until the Permian period, about 225 million 
 years ago, when they became extinct. Blastoids are 
 beautiful fossils which look much like small hickory 
 nuts. 
 
 They most commonly are found in the river cliffs 
 and stream banks of western and southwestern Illi- 
 nois, especially in Randolph County, and in southern 
 Illinois near the Ohio River. 
 
 CYSTOIDS (sis-toyds, plate 9). Cystoids are re- 
 lated to the crinoids and blastoids but are more 
 primitive than either. The body, or calyx, is not 
 nearly so well developed and the arms are irregu- 
 lar and rarely preserved. Nearly all cystoids are 
 stemless and the body plates are quite irregular 
 in arrangement. 
 
 The cystoids lived from the Ordovician period, 
 400 million years ago, until the Mississippian per- 
 iod, 300 million years ago. 
 
 Most cystoids found in Illinois come from quar- 
 ries in the Silurian rocks in the Chicago region and 
 in the Mississippi River bluffs of northwestern Il- 
 linois. 
 
 30 
 
Ordovician Graptolite 
 
 GRAPTOLITES 
 (grap -toe -lite s, 
 plate 9). The grap- 
 tolites were a very 
 simple kind of ma- 
 rine animal that 
 appeared in the 
 Cambrian period. 
 They became abun- 
 dant in Ordovician 
 and Silurian time 
 but gradually died out, 
 The last ones lived during the Mississippian period. 
 The animals lived in tiny chitinous cups arranged 
 along slender stems. In some forms the stem was 
 attached to a round float, and in others two, three, 
 or four stems might be attached together. Most 
 graptolites floated free in the oceans and were 
 scattered throughout the world. 
 
 As fossils, they look like little black lines with 
 saw-tooth edges. They are found mainly in shales 
 but also occur in limestones. In Illinois they are 
 most common in Ordovician rocks of the northern 
 part of the State. 
 
 CONODONTS(ko^no-donts, 
 plate 10). Conodonts are 
 small fossils which bare- 
 ly can be seen by the na- 
 ked eye. Almost nothing is 
 known about the animal 
 these beautiful amber-colored tooth-like little fos- 
 sils came from. 
 
 Even though we don't know much about them, co- 
 nodonts are of value because they help geologists 
 determine the age of the rocks in which they are 
 found. 
 
 Mississippian 
 Conodont (40 x 
 
 31 
 
Lepidodendron 2/5 X 
 
 Annularia 2/5 x 
 
 VERTEBRATE FOSSILS 
 
 Mammoth tooth i/gX 
 
 
 tevrts«| 
 
 Stigmaria 2/gX 
 
 Mastodon tooth '/ 6 X 
 
 Plate fO 
 
Conodonts of the same type are found over much 
 of the world in rocks of the same age, leading us to 
 believe that the animal was a good swimmer and 
 could cover great distances. Because of this, we 
 think these fossils may be those of an extinct fish. 
 
 Conodonts have been found in rocks ranging from 
 the Cambrian to the Trias sic. They are found in 
 bedrock formations throughout Illinois. 
 
 PLANT FOSSILS 
 (plate 10). Of all the fos- 
 sils that have been found 
 in Illinois, perhaps none 
 are more famous than the 
 fossil leaves and other 
 plant remains from the 
 world-renowned Mazon 
 Creek area in northeast- 
 ern Illinois. 
 
 In this area, which lies 
 in Grundy and Will coun- 
 ties, iron carbonate nod- 
 ules containing plant re- 
 mains are found in the 
 waste piles of strip and 
 underground mines and at 
 places along Mazon Creek. 
 
 The plant fossils are 
 remains of fast-growing 
 ferns and trees. In the 
 damp lowlands and swamps that covered Illinois dur - 
 ing the Coal Age, they formed a dense growth and 
 were preserved in our coal beds. 
 
 In the jungle -like growth the plants most common 
 were huge ferns that had fronds five or six feet 
 long and grew to a height of more than 50 feet. Along 
 with them were seed ferns, now extinct, and giant 
 
 33 
 
 Lepidodendron 
 
 A Pennsylvanian 
 
 Scale Tree 
 
scouring rushes, descendants of which are the small 
 horsetail rushes that live today along our wooded 
 streams. You can recognize scouring rushes by their 
 jointed trunks and the leaf whorls, common in the 
 Mazon Creek nodules. 
 
 The most imposing plants of the Coal Age forests 
 were the scale trees, which grew to heights of 100 
 feet or more. Close-set leaves grew on their trunks 
 and limbs, and when the leaves fell off they left rows 
 of scars that are the identifying marks for the trees. 
 Diagonal rows of scars identify the Lepidodendron 
 and vertical rows identify the Sigi/laria. 
 
 VERTEBRATE FOSSILS (plate 10). Animals 
 with backbones are called vertebrates. They include 
 reptiles, amphibians, fish, birds, and mammals. 
 
 In many western states, vertebrate fossils, such 
 as skeletons of dinosaurs, camels, and saber-toothed 
 tigers, are common inMesozoic and Cenozoic rocks 
 (see Geologic Time Chart, page 2). 
 
 IfMesozoic and Cenozoic rocks were ever depos- 
 ited in Illinois, they have been removed by erosion. 
 As a result, the vertebrate fossils found in our 
 State are restricted to Paleozoic and Pleistocene 
 rocks. 
 
 The Paleozoic vertebrate fossils are fish teeth, 
 scales, and bony plates, a few lizards, and amphi- 
 bians. The Pleistocene vertebrates included many 
 forms now extinct, such as mammoth and mastodons, 
 and many forms still living in this region, including 
 man. 
 
 34 
 
BOOKS ABOUT FOSSILS 
 
 FIRST BOOK OF PREHISTORIC 
 ANIMALS. Alice Dickinson. Frank- 
 lin Watts, Inc., New York, 1954. 
 
 A beautiful little book for grade 
 school age. Well written and well 
 illustrated. 
 
 HOW THE WORLD BEGAN. Edith 
 Heal. Thomas S. Rockwell Co., 
 Chicago, 1930. 
 
 The story of the beginning of life 
 on earth. For advanced grades 
 through high school. 
 
 THE STORY OF OUR ANCESTORS. 
 May Edel. Little, Brown and Co., 
 Boston, 1955. 
 
 Tells how man grew into the 
 strange upright creature that he is 
 with nimble fingers and giant brain. 
 For junior high and high school. 
 
 LIFE LONG AGO. Carroll Lane 
 Fenton. The John Day Co., New 
 York, 1937. 
 
 One of the very best books for 
 advanced grade and junior high. 
 
 STORIES READ FROM THE ROCKS. 
 Bertha Morris Parker. Basic Sci- 
 ence Education Series. Row, Pet- 
 erson and Co., Evanston, 111., 1942. 
 Advanced grade and junior high. 
 
 ANIMALS OF YESTERDAY. Bertha 
 Morris Parker. Basic Science Ed- 
 ucation Series. Row, Peterson and 
 Co., Evanston, 111., 1948. 
 
 Advanced grade and junior high. 
 
 COMMON FOSSILS OF MISSOURI. 
 A. G. Unklesbay, University of Mis - 
 souri Bulletin, Handbook 4, Colum- 
 bia, Mo., 1955. 
 
 OHIO FOSSILS. A. LaRocque and 
 M. F. Marple. Ohio Division of 
 Geological Survey Bulletin 54, 
 Columbus, Ohio, 1955. 
 
 A popular account of fossils 
 written especially for the amateur. 
 It has several keys for identifica- 
 tion of fossils. 
 
 LIFE OF THE PAST. G. G. Simp- 
 son. Yale University Press, New 
 Haven, Conn., 1953. 
 
 A broad and very readable in- 
 troduction to the study of fossils. 
 
 PREHISTORIC ANIMALS. William 
 E. Scheele. World Publishing Co., 
 Cleveland, Ohio, 1954. 
 
 A beautifully illustrated book for 
 all ages. 
 
 THE WORLD WE LIVE IN. Time, 
 Inc. (distributed by Simon and 
 Schuster, Inc., New York), 1955. 
 
 A superb general survey of the 
 world of nature. Two chapters are 
 devoted to life of the past. 
 
 DINOSAUR BOOK. E. H. Colbert, 
 American Museum of Natural His- 
 tory, New York, 1945. 
 
 Excellent popular summary of 
 our knowledge of dinosaurs. For 
 all age levels . 
 
 HANDBOOK OF PALEONTOLOGY 
 FOR BEGINNERS AND AMATEURS 
 Winifred Goldring. New York State 
 Museum, Albany, N. Y., 1929. 
 
 A summary of paleontology for 
 adults. 
 
 FIELDBOOK OF ILLINOIS LAND 
 SNAILS. Frank Collins Baker. II- 
 
linois Natural History Survey Man- 
 ual 2, Urbana, 111., 1934. 
 
 A beautifully illustrated booklet 
 that will aid in identifying most 
 Pleistocene snails. 
 
 INTRODUCTION TO HISTORICAL 
 GEOLOGY. R.C. Moore, McGraw- 
 Hill Book Co., New York, 1949. 
 
 A general account of earth his- 
 tory and organic evolution. Adult 
 level. 
 
 AN INTRODUCTION TOPALEON- 
 TOLOGY. A. Morley Davis. Thomas 
 Murby and Co., London, 1947. 
 
 A somewhat simplified outline 
 of the major fossil groups. 
 
 MAN AND THE VERTEBRATES. 
 A. S. Roemer, University of Chi- 
 cago Press, Chicago, 1941. 
 
 A well illustrated introduction 
 to living and fossil vertebrates. 
 
 ANCIENT PLANTS AND THE 
 WORLD THEY LIVE IN. H. N.An- 
 drews. Comstock Publishing Co., 
 Ithaca, N. Y., 1947. 
 College level. 
 
 PRINCIPLES OF INVERTEBRATE 
 PALEONTOLOGY. R. R. Shrock 
 and W. H. Twenhofel. McGraw-Hill 
 Book Co., New York, 1953. 
 
 Technical college-level textbook. 
 
 INVERTEBRATE FOSSILS. R. C. 
 Moore, Cecil Lalicker, and A. 
 Fischer. McGraw-Hill Book Co., 
 New York, 1953. 
 
 College text. Well illustrated. 
 
 INDEX FOSSILS OF NORTH AM- 
 ERICA. H. H. Shimer and R. R. 
 Shrock. John Wiley and Sons, New 
 York, 1945. 
 
 Useful for the identification of 
 most invertebrate fossils. 
 
EDUCATIONAL EXTENSION PROGRAM 
 
 The Educational Extension Division of the Illinois 
 State Geological Survey contacts the public through 
 a number of channels, including nontechnical pub- 
 lications, rock and mineral collections for Illinois 
 schools and educational groups, lectures, exhibits , 
 correspondence involving identification of rocks 
 and minerals, news items for the press, and field 
 trips. 
 
 During each year six field trips aregiven, in wide- 
 ly separated parts of the State, for teachers, stu- 
 dents, and laymen. The general program is espe- 
 cially designed to assist in teaching the earth sci- 
 ences and help make Illinois citizens aware of the 
 State's great mineral wealth. 
 
 Illinois State Geological Survey 
 Urbana, Illinois 
 
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