mmm I— -eruvian expeditions, 1911-1915, Publications, no. 19, 38 Peru ' Y^IE«¥MIIYM&SinrY« 1921 [From The American Journal op Science, Voi,. XXXVII, February, 1914] YALE UKiV£.rfiSii MOV B ii,Li LIBRARY GEOLOGIC RECONNAISSANCE of the AYUSBAMBA (PERU) FOSSIL BEDS By Herbert E. Gregory VERTEBRATE FOSSILS from AYUSBAMBA, PERU By George F. Eaton. With plates V, VI, VII. (Results of the Peruvian Expedition of J9J2 under the auspices of Yale University and the National Geographic Society.) THE AMERICAN JOURNAL OF SCIENCE [FOURTH SERIES.] Art. VIII. — Geologic Reconnaissance of the Ayusbamba {Peru) Fossil Beds / by Herbert E. Gregory.* Introduction. Ok the basis of information furnished by Dr. A. A. Giesecke, President of the University of Cuzco, a preliminary excursion to the hacienda of Ayusbamba, province of Paruro, was made by Dr. George F. Eaton in October, 1912. The object of this visit was to investigate the reported discovery of fossil vertebrate remains. The region appeared to Dr. Eaton of sufficient interest to warrant further field work, and accord ingly, under instructions from the Director of the Peruvian expedition, arrangements were made for a week's study of the Ayusbamba area. The party which left Cuzco on November 13, 1912, equipped for geologic and topographic work, and for making collections of fossils, consisted of Herbert E. Gregory, geologist; George F. Eaton, osteologist; K. C. Heald and Carlos Duque, topographers ; and Jose Gabriel Cosio, professor of Sociology and History in the University of Cuzco. Geography. From Cuzco the trail to Ayusbamba enters the valley of the Huancaro, and follows the south branch of that stream^ to its source in the bogs of the upper plateau, at an elevation of 13,500 feet. Passing over the gracefully molded, grass-floored highland which marks the upper extent of the tributaries of the Rio Huatanay, the trail enters the Apurimac watershed. Perched high on mountain flanks, heading canyons, traversing fields of yareta, and zigzagging among glacial bowlders, along spurs and down talus slopes, the-^M^^jndUts way toward * Geologist, Peruvian Expplitila^gf lfi2. V Am Jour Sci.— Fourth Series, Vol. XXXVII, No. 218.— February. 1914. 10 126 U.E. Gregory — Geologic Reconnaissance of the the Apurimac River and finally emerges at the hacienda of Ayusbamba, ten leagues south of Cuzco (fig. 1). For genera tions this trail has been the main avenue of approach to the sacred city from the upper Apurimac valley, and the artificial pavements, terraced descents, and trenched hillsides give evi dence of an originally well-planned highway, whose construc tion involved a prodigious amount of physical labor, the value of which is greatly reduced by the present neglect of mainten ance. In traversing this route from Cuzco to Ayusbamba, one is impressed by the thought that the llamas and picturesque Indians met on the trail, the grass-covered slopes, the cacti and tenaceous shrubs along the path and bordering the artificial Fig. l. v\ ) 14 J i! / V % i fe /* X 3p „$0^ fccoyp /O^^oisDarnbaj^^^ \ Fossil/Local ity Naytiual _ — ^*^ Fig. 1. Index map, showing location of Ayusbamba. walls, the wonderfully beautiful native flowers which carpet the bowl-like upper valleys, and the long vistas of canyon and slope present a picture essentially identical with that viewed by Inca and pre-Inca travelers. For eight or ten centuries this well-worn path has marked the passage of llama trains and patient Quichua cargadores bearing materials of trade to and from Cuzco. Along the route are several squalid villages — groups of thatched adobe or stone huts — the homes of the Andean shep herds. Midway between Cuzco and Ayusbamba the trail makes a descent of 2000 feet and passes through Yaurisque at a point where a canyoned stream is joined by two short, wide valleys. The limestone soil, abundant water and sheltered Ayusbamba (Peru) Fossil Reds. 127 position of this valley afford opportunity for the cultivation of ffl ' rte?i vefet^bleS and grains, while the adjoining slopes and highlands furnish admirable pasturage. When viewed from the trail perched high above the lillage, the deeply trenched canyon along which a swift stream winds its way through a tangle of shrubs, the abrupt slopes of brown Fio. 2. Fig. 2. View of the village of Yauriska, looking north. sandstone dotted with hardy plants, and the graceful outlines of the mountains beyond, compose an attractive landscape (fig. 2). The masses of color presented by field and ledge and native, vegetation are pleasantly modified by scattering Euca lypti and a profusion of flowers along the walls and in the better-kept gardens. The village itself — about one hundred, tile-roofed, mud-walled houses, arranged along a cobble-paved 128 H. E. Gregory — Geologic Reconnaissance of the street and adjoined by yards surrounded with forbidding, cactus-covered walls — is in harmony with its topographic set ting. However, too close inspection of the village and its inhabitants may detract from the picture, for, in spite of hos pitality of priest and official and the evident desire to honor the stranger, it is difficult to overlook the dirt and squalor, the intimate association of man and beast, and the palpably unwholesome manner of life in this typical Andean settlement. The village of Ccoypa, while not so beautiful as Yaurisque, is equally interesting, especially as regards its location. Situ ated at the base of a talus slope, the houses of Ccoypa are built among bowlders whose size almost equals that of the individual dwellings, and the streets and the passages constitute a laby rinth which puzzles the stranger. The hacienda of Ayusbamba, the objective point of our geological excursion, is a typical residence of the wealthier landed proprietor on the Andean plateau. A one-story build ing of stone, adobe and tile surrounds a spacious patio. The sun-warmed rooms on the north side, including a sala of gener ous proportions, are occupied by the family. The other parts of the building are devoted to store rooms and stables. Inti mately connected with the main building are corrals for stock, and a scattering group of huts which house the workmen and their families: " At the north, and entered from the sala, is the garden, bordered by towering Eucalypti and including flowers and shrubs remarkable for abundance, variety, and individual merit. To me the most attractive feature of this hospitable home is the view from the garden terrace northward across the Chipura chasm to the terraced, fields of Ccoypa, and northwestward across the Mollemolle into the magnificent can yon of the Apurimac (figs. 3 and 4). These views, though uncommon among the world's scenic features, are characteristic of the Peruvian Andes. The hacienda has its own supply of food, fuel and material for clothing, and has workmen skilled in various trades. Little needs to be bought and little is sold ; the place is commercially almost self-sufficient. The Indians, young and old, are not merely hired servants, but are attached to the hacienda by various ties. The relation of senor to ser vants and workmen, and the general regime at Ayusbamba, remind one forcibly of a mediaeval feudal estate in which independence and hospitality were closely mingled. General Geologic Relations. The area including Ayusbamba possesses great relief. The lower reaches of the smaller streams (Vellile, Mollemolle, and" Chipura) are bordered by steep, frequently precipitous slopes and the master stream, the Apurimac, whose volume goes to Ayusbamba (Peru) Fossil Beds. 129 swell the Amazon, has entrenched itself 4000 feet below the general level. In passing from Cuzco to Ayusbamba the divid ing flats and low ridges form a roughly level surface extending over sedimentary beds in various attitudes, and of unequal Fig. 3. Fig 3 View from Senor Calvo's garden looking north across the Chi pura gorge. The trail to Cuzco traverses the rock terrace, passes through the village of Ccoypa and ascends the valley of the Mollemolle. resistance to erosion. Although deeply dissected, the highland area suggests a widespread though imperfectly developed pene plain resulting from erosion in late Mesozoic time. Where unaffected by glaciation, the valleys cut into this ancient, base- leveled floor have reached a stage of development approaching 130 H. E. Gregory — Geologic Reconnaissance of the maturity. A glance into the Apurimac canyon (fig. 5) shows that the present valley form has by no means been attained by regular progressive growth within a single cycle. At least two rock benches and two alluvial terraces occupied by small Fig. 4. Fig. 4. View from Senor Calvo's garden, looking northwestward, down the Mollemolle into the Apurimac canyon. Andean villages mark the valley wall, — facts which indicate an involved physiographic history whose episodes await inter pretation. The higher mountain valleys are flat-floored, wide open bounded by steeply-sloping walls which join the plateau sur face at an abrupt angle. To these evidences of glaciation may Ayusbamba (Peru) Fossil Beds. 131 be added morainal accumulations and the ungraded character of the upper stream courses, which are in marked contrast with their lower reaches. So far as observed, direct abrasion by glaciers was not effective below 12,500 or at most 12,300 feet. The mountain heights above the lower limit of ice action pre- Fig. 5. Fig 5 View from the Pass at the southern edge of the Ayusbamba fossil beds, looking south into the Apurimac canyon. Note the rock and alluvial terraces. sent both rounded bosses and sharp aretes,— features character istic of glaciated surfaces. Summits below 12,300 feet assume forms consistent with the role which they play as part of a sub- maturely developed landscape. Along the highland trails north from Ayusbamba and also east toward Paruro irregu larly distributed erratics, incipient cirques, bowlder trains, and 132 H. E. Gregory — Geologic Reconnaissance of the interrupted drainage speak of a widespread glaciation which has substantially modified the pre-Pleistocene topography. The bedrock of the whole region between the Apurimac and Cuzco valleys is brown and grey sandstone, whose continuity of stratification is interrupted by lenses of conglomerate and occasional beds of shale. The sandstone strata rarely approach horizontality ; dips of 20°-40° are common, and where expos ures are favorable these tilted strata are seen in folds open or closed, and with horizontal or steeply inclined axes. Near the headwaters of the Mollemolle exposures of dense blue-grey limestone, much fractured and in places brecciated, roughen the hill-slopes. This rock, in common with the sandstone, appears to be identical in lithologic character with the strata represented in the Huatanay valley, and the single fossil (Lower Cretaceous) obtained from the limestone is a duplicate of many collected at Cuzco. The Lower Cretaceous limestone overlies strata of sandstone of great extent and more than looO feet in thickness. The relations existing between the calcare ous and arenaceous beds have not been determined. Strata containing carbonized plant fragments and unconformably overlying the brown sandstone were found near the village of Paruro, and assigned by Duenas* to the Tertiary. The reasons for such a conclusion are not given, and so far as the writer is aware the only paleontologic evidence of age relations consists of a Lower Cretaceous lamellibranch, and the vertebrate re mains from Ayusbamba described by Dr. Eaton. With the exception of intrusives cutting the Apurimac can yon wall, no igneous masses were observed, although, as stated below, it is probable that a boss of diorite lies buried beneath the superficial deposits at Ayusbamba. Duenas found that diorite intersected by dikes of red and green labradorite con taining phenocrysts of augite was associated with the ever- present grey and brown sandstone at several localities in the province ot Paruro. The discovery of coal in the vicinity of Paruro has from time to time been announced. The basis for such reports is doubt less the presence of carbonized wood and lenses of impure lig- nitic peat which occur among the strata of ancient lake beds. My observations are in accord with the results of a reconnais sance conducted by Peters and Company, and with the conclu sion of Duenas, that the quantity of the so-called '• coal " is negligible and its quality unsatisfactory. Rock for building, lime for cement, and excellent clay, all of which may be ob tained in quantity, complete the list of rocks of economic value in the Avusbauiba region. * Boletin Cuerpo de Eng. de Min. del Peru, No. o)!, 1907, p. 122. Ayusbamba (Peru) Fossil Beds. 133 The Ayusbamba Lake Area. General relations.— The Ayusbamba lake deposits cover an area of about one-eighth of a square mile (see map, fig. 8), situated in an unusual position, at the top of the pass traversed by the trail from Ccoypa in the Mollemolle valley to Bilcokyma, a tiny pueblo perched on a terrace within the Apurimac canyon. The depression containing the fossil beds is walled in on the east by sandstone ridges rising 800' above the center; the ledges forming the west border are deeply buried in superficial debris. At the north the lacustrine deposits are abruptly ter- Fig. 6. Fig. 6. View of Ayusbamba fossil beds, looking south-southwest, toward the pass into the Apurimac valley. Note the attitude .of the strata. minated by a steep slope developed by vigorous headward erosion of a tributary to the Chipura. Fringing the rock bor ders on the west, south, and east are slopes of surface wash and fans more or less dissected, which in turn overlap the clays of the central part of the depression. The surface of the lacustrine deposits (fig. 6 and map, fig. 8) slopes northwestward, and the streams which drain the area unite to form an outlet channel which, after passing through a narrow, vertically walled gorge 30 feet deep, makes an abrupt descent by a series of rapids and waterfalls to join the Chipura and finally the Apurimac. A much shorter course with much 134 H. E. Gregory — Geologic Reconnaissance of the steeper gradient, — a course leading south directly to the Apuri mac, — is being established by headward erosion, and the divide has migrated eastward within recent times (fig. 7). Dissection of the lacustrine beds has been accomplished by Calvo brook,* consisting of two streams which unite to form the main outlet channel. The valley of Calvo brook presents youthful features both along its larger branches and in the innumerable tiny canyons cut in clays and sands. About one-third of the interstream spaces consists of imperfectly Fig. 7. Fig. 7. View of fossil locality, looking southwestward across the divide between Calvo brook and the Apurimac river. The divide is migrating toward Calvo brook. Photograph by G. F. Eaton. drained grass plats; the remaining portion is marked by "bad land" slopes and mounds cut by canyons 30-40 feet deep, two to ten feet wide, producing a surface difficult to traverse. Surficial erosion is augmented by numerous springs and seeps, emerging at the contact of clay and sand. Landslides are of frequent occurrence and greatly facilitate the removal of the lacustrine deposits. Ancient corrals and andenes point to for mer human occupation, and their position shows that a consid erable part of the tillable land has been lost through recent stream erosion, * The liberty has been taken of naming this stream in honor of Senor Eme- terio Calvo, the hospitable proprietor of hacienda Ayusbamba. Ayusbamba (Peru)' Fossil Beds. 135 Bed rock; — The lake beds at Ayusbamba rest on sandstone coated with a layer of coarse bowlders and followed upwards by clays, sands, ash and peat, above which, near the edges of the basin, are unstratified angular gravels distributed as fans and surface wash. The rock floor is exposed on the north and on the south rimsof the basin and in the beds of several of the minor stream branches. The bed rock is essentially sandstone, brown or grey in tone, especially on weathered sur faces. The strata, which vary from 6 inches to 20 feet in thickness, rarely maintain their individuality for more than 100 feet along the strike, and may be considered as a series of lenses whose dimensions and texture are subject to abrupt changes. Angular cross bedding is a noticeable feature in the medium-grained sandstone, and sun-baked surfaces were observed on the bedding planes of the shaly limestone. A number of minute faults were noted. While the rock ledges underlying and surrounding the ancient lake basin may roughly be grouped as sandstones, there is considerable variation in texture and composition as indicated by the following rock types represented : (1) Sandstone, very fine, even-grained, composed of quartz grains of microscopic size embedded in siiicious cement. (2) Sandstone, medium to coarse-grained, consisting of sub- angular and angular fragments of white quartz, feldspar crys tals, diorite-porphyry, sandstone, and rare limestone ; bound together by silica. (3) Thin lenses of purple-brown, arenaceous, shaly lime stone. (4) Conglomerate with pebbles the size of buck shot and upwards. The finer-grained phases of the conglomerate grade into sandstones and consist of the same materials ; but in the ledges facing the Chipura the pebbles are larger (1/4" to 3" in diameter ; one dacite bowlder measured 2'), and are distributed as broken strings or as individuals embedded in a cubic foot or cubic yard of sandstone matrix. The larger pebbles compos ing the conglomerate at this locality include quartzite, biotite- granite with orthoclase phenocrysts and a dark grey igneous rock with granitic and porphyritic facies. The last-named rock which is not only a constituent of the conglomerate but is present in the overlying bowlder bed and occurs in fragments of various sizes dotting the surface southwest of the hacienda buildings, is worthy of special notice. A hand speci men of this rock is seen to consist essentially of crystals of hornblende, $" to i" in length, embedded in a groundmass of crystals of microscopic size. A few pyroxene crystals are also present as phenocrysts. Microscopic examination of the 136 H. E. Gregory— Geologic Meoonnaissanoe of the groundmass reveals the presence of plagioclase feldspar, bio- tite and magnetite in addition to much hornblende and a limited amount of pyroxene. Fragments of calcite and of an unde termined zeolite were observed in one of the three sections Fig. 8. the peruvian expedition of 1912 UNDER THE AUSPICES OF YALE UNIVERSITY & THE NATIONAL GEOGRAPHIC SOCIETY HIRAM BINGHAM. DIRECTOR MAP OF A PORTION OF THE PROVINCE OF PARURO, PERU SHOWING FOSSIL LOCALITY NEAR AYUSBAMBA Topography by K C Heald and Carlos Duque Con-tou,r irvterua-l 20 feet. Da,tusi\, sea, level f levels bnoixgM from, Cuzco t(y aner-oitl) Geology by Herbert E Gregory Shaded area indicates i_acustrine deposits examined. The rock is therefore to be classed with dioritic or andesitic porphyries. The relative abundance and localiza tion of these diorite bowlders suggest the possibility that an intrusive mass now covered by superficial debris exists to the west of Calvo brook. The structural relations of the sandstones were not studied in sufficient detail to permit of a definite statement regarding Ayusbamba (Peru) Fossil Beds. 137 their origin and conditions of deposition. However, the irregularity of bedding, the abrupt change in composition and texture along strike, the predominance of subangular bowlders, the type of cross bedding, the presence of sun-baked surfaces, and the brown color of the rock suggest continental rather than marine sedimentation. Bowlder Bed. — Directly overlying bed rock and immediately beneath lacustrine clays and sands, a bowlder bed is exposed at a few ' localities. The pebbles, all subangular, are chiefly igneous, and include the following varieties : Andesite, dense and scoriaceous ; diorite-porphyry ; granite-porphyry ; rare granite ; black and green hornstone ; black, pink, and gray quartzites ; brown and red sandstones. About eighty per cent of the bowlders measure between one and six inches ; the largest seen in place is four feet in diameter, although larger blocks are embedded in the banks of Calvo brook. In places the bowlder bed is loosely compacted ; elsewhere so firmly cemented that pebbles may be broken without disturbing the matrix. The exposures of bowlder bed studied gave no cer tain clue as to origin. The heterogeneous character of the mass, both as regards composition and stratification, suggest morainal accumulations, yet striated bowlders and scoured floor were not observed. Part of the material might well have been supplied as talus, but with the exception of sandstone fragments the bowlders are of types not represented in the country rocks. The history of the bowlder beds cannot be written on the basis of present knowledge of the Apurimac valley region. Lacustrine Beds (Map, fig. 8). — The lake beds proper — clay, fine sand, ash, and peat — rest in some places upon the bowlder bed ; elsewhere directly upon the sandstone floor. The strata, dip slightly toward the center of the basin, but with many variations and exceptions. The northward dip is in general greater and suggests a tilting of the beds at a time postdating their deposition. The stratigraphic succession of the lacustrine beds is shown in the following selected sections : Section I. West branch Calvo brook. 200' from junction. Dip of clay beds NEZ 10°. Feet 1 . Grass-covered slope of superficial debris 3 Unconformity. 2. Sand, fine, with lenses of coarse sand and of adobe, con taining plant roots ; a f e w thin clay layers 30 3. Volcanic ash, excessively fine, soft, pure white, regu larly stratified in beds about one-tenth of an inch thick - ! 138 EC. E. Gregory — Geologic Reconnaissance of the 4. Sand, fine, even-bedded, thin-bedded, with four strata of pink clay (aggregating 3') composed of layers about one-fiftieth of an inch thick 13 5. Sand and clay like No. 4 in alternating beds. Includes a lens 1" thick, 50' long, of black iron-cemented sand, 10 6. Clay, brown, thin, even-bedded, and fine sand. Few bone fragments. Total clay about 60 feet ; sand 35 feet - 95 V. Coarse sand, firmly cemented, forms bench 0-3 8. Sand, fine, thin-bedded 10 9. Sand, fine, containing three lenses and one 3" bed of sand and clay firmly cemented by lime and contain ing abundant bone fragments 6 10. Sands, fine, thin-bedded, with small amount of clay.. 15 183-3 Section II. East branch Calvo brook. 100 feet from junction. Feet 1. Soil, — brown, mixture of gravel and sand 15 2. Sand and fine gravel, containing numerous carbonized fragments of plants 3 3. Peat, brown, porous, mixed with mud; plants too frag mentary for determination 025 Unconformity. 4. Gravel, composed of angular pebbles one-half inch to four inches in diameter 1-5 Unconformity. 5. Sand, with small amount of thin-bedded clay, yellow, traversed by carbonized roots and root-tubes; prob ably an old soil _ 3 6. Clay, light brown; and sand, fine, clear, in alternate, very thin strata. Clay and sand about equal in amount 30 52-75 Section III. West branch of East branch of Calvo brook. Dip NZ 2°. _. , _, Feet 1. Gravel, and sand; surface wash 5 2. Gravel and fine sand, grey; loosely cemented by iron. 2 Unconformity. 3. Clay, very thin, even layers, forming strata three inches to one foot thick, which alternate with strata of fine sand. A few decomposed bones ¦. 10 4. Volcanic ash, white, microscopically fine-grained, thin- bedded, porous. Locally called "chalk" 1-5 5. Clay and sand, very thin layers grouped in alternate strata _. c 26-5 Ayusbamba (Peru) Fossil Beds. 139 Notes on measured sections. — The individual clay beds are nowhere thick and at all places are interbedded with fine sand. At the north edge of the basin, where 135 feet of lacustrine deposits are exposed, the section consists of alternating layers, one-tenth of an inch to four inches thick, of fine sand and banded, dark red clay in the midst of which occur three lenses of coarse sand. The layers of sand and clay interleave as lenses fifty to two hundred feet long. Minute folds and faults further interrupt the regularity of bedding. The clays are red, pink, or brown in tone, due to their content of ferric iron in hydrated form, and are believed to owe their origin to the decomposition of the surrounding pre-Cretaceous sandstones. No "claydogsj' or concretions were observed, but a few small, light-colored patches in the clays are highly calcareous in marked contrast to the clay in general. Apparently the process of segregation is in operation at the present time. The regularly banded white ash, interstratified with the clays, decomposes under slight pressure to an impalpable powder which has a gritty " feel." Microscopical study of this rock revealed the presence of glass arranged as threads and cusps and hooks, and constituting about 90 per cent of the mass ; laths of plagioclase and frayed ribbons of biotite complete the list of component minerals, and determine the classification of the deposit as dacitic ash. No true peat or coal was found among the beds, but at sev eral localities thin bands of an earthy mixture of sand, clay, and vegetable fragments were noted. This mixture was found by microscopic examination to consist of minute shreds of glass, tiny feldspar, quartz, biotite and muscovite fragments, together with broken bits of volcanic ash and portions of eal- cite crystals. The plant remains present were too fragmentary for determination. The remains of vertebrates are found among the upper grav els, on floors of tiny ravines, and embedded in clay or sand layers. The content of the calcareous sand lenses (No. 9, Sec tion I), commonly a mixture of sand, lime, and clay, is in places fully one half bone fragments. Bones are widely scattered horizontally, and in a given locality may be found unrelated parts of a skeleton mingled with bones of animals belonging to entirely different species. No entire skeletons were found in place, and it is probable that several feet of strata intervene between portions of the same carcass. The species represented by parts of skeletons are listed and described by JDr. Eaton (pp. 144-154 following). Field evidence justifies the conclusion that bones of animals which died on shore or floundered in bogs or quicksand were redistributed by surface wash and running water. 140 H. E. Gregory — Ayusbamba Fossil Beds. Origin and character of Lake Ayusbamba. — From the sec tions and descriptions given above it is evident that we are dealing with deposits which in part are truly lacustrine, — material laid down in a body of quiet water which existed for a relatively long period of time. On the assumption that each layer of sand and of clay represents the amount deposited during a single, rainy season, approximately 100,000 years would be required for the accumulation of the materials ex posed in the present fragmentary sections. It is probable that the lake beds had greater thickness. That they formerly extended much farther northward is shown by an unprotected, truncated section including 185 feet of strata perched high on the valley side overlooking the Chipura river. The containing wall of rock is complete except on the north side, where it has been entirely removed. Unlike the remaining portions of the rim, the north wall probably consisted of fluvial and glacial debris washed from the highlands. Moraines extend to the edge of the present lake deposits and may have formed the original barrier. During the life of the lake, fans from the high ridge at the south encroached upon its waters and sepa rated the original sheet into more or less detached bogs. This process, combined with the development of a channel through the unconsolidated northern barrier, led to the extinction of the water body. Judging from the physical data at hand, this mountain tarn may have beautified the landscape of the late Pliocene or any portion of the early Pleistocene epoch, — a con clusion which is in harmony with the paleontological evidence.* Ancient Lake Ayusbamba is not an isolated case of extinct water bodies in Peru. DueBasf speaks of similar deposits near the pueblo of Paruro, and the unpublished reports of engi neers and travelers indicate the existence of unexplored Tertiary and Pleistocene deposits scattered over the Andean highlands. * See the following article by Dr. George F. Eaton, pp. 141 to 154. f Loo. cit. Eaton— Ve?-tebrate Fossils from Ayusbamba, Peru. 141 Art. IX. — Vertebrate Fossils from Ayusbamba, Peru ; by George F. E*ton * With Plates V, VI, VII. _ "While engaged upon the field-work of the Peruvian Expedi tion of 1912, I had the pleasure of accompanying Dr. Albert Giesecke, President of the University of Cuzco, on a hasty visit to a locality near Ayusbamba, among the mountains about thirty miles south of Cuzco, where he had previously obtained some fragmentary vertebrate fossils. On this occasion a few hours only could be spent in the field ; but as it seemed prob able that by going over the ground carefully, further material might be secured, Professor Bingham, the Director of the Expedition, gave his consent to my making another visit to the locality, this time in company with Professor Gregory, the geologist, Mr. K. C. Heald, assistant topographer, and Mr. C. Duque. Although other important work caused the post ponement of this trip until- the middle of November, when the rainy season, unfavorable to fossil-hunting in the moun tains, had set in, we were able to obtain material of consider able value during the brief time our party was in the field. To Sr. Emeterio Calvo, the master of the delightful hacienda Ayusbamba, I owe my sincere thanks, not only for permission to collect upon his land, but also for the generous hospitality extended to our party. The fossils that form the subject of these notes occurred at an altitude of about 12,400 feet, in gravel and clay beds and in surface-wash along, the southern margin of a small lake, the original contours of which are partially indicated in the map (fig. 8) accompanying the preceding article by Professor Gregory. An excellent view, looking southerly across the fossil grounds, appears as fig. 6 of Professor Gregory's report. Very nearly the reverse view (N. 5° E. Mag.) taken from the south rim of the basin, is shown in text^-figure 1 of the present article. After taking this photograph the camera was turned a little to the right' (N. 30° E.) and the view shown in text- figure 2 was taken. These two views together cover practically all of the fossil grounds. Almost at the exact center of Professor Gregory's fig. 6, a mastodon's blade bone was found. The nearer view' of this spot (text-figure 3) is equally charac teristic of several other places where fossils occurred. In this photograph, taken while waiting for the protective jacket of burlap and plaster to dry, appears one of our faithful arrieros whose interest in collecting fossils made him very helpful. With few exceptions, fractured and dissociated material only * Osteologist of the Peruvian Expedition of 1912. Am Jour Sci.— Fourth Series, Vol. XXXVII, No. 218.— February, 1914. 11 142 Eaton— Vertebrate Fossils from Ayusbamba, Peru. was found. This indicates clearly that, in most cases, the bones of animals, perishing near the borders of this ancient lake, were widely scattered before being finally covered by alluvium from the neighboring heights. It is possible that Fig. 1. Fig. 1. View N. 5° margin of the basin. E. over Ayusbamba fossil beds from the southern some of this vertebrate material may have been originally embedded at a slightly higher level. I see no reason, however, to question the contemporaneity of the extinct species of animals represented in this collection. No vertebrate fossils had been previously described from this part of the Peruvian Andes. Therefore every recognizable specimen, that might add to our Eaton— Vertebrate Fossils from Ayusbamba, Peru. 143 wXnt 1 0Vthe.fextlnc* fauna of the ^gion, was collected, S f