CM (D o T" CD ii m • J. PIERPONT MORGAN PUBLICATION FUND REPORTS OF THE PRINCETON UNIVERSITY EXPEDITIONS TO PATAGONIA, 1896-1899 J. B. HATCHER IN CHARGE EDITED BY WILLIAM B. SCOTT BLAIR PROFESSOR OF GEOLOGY AND PAL/EONTOLOGY, PRINCETON UNIVERSITY VOLUME V. PALEONTOLOGY II. PRINCETON, N. J. THE UNIVERSITY STUTTGART SCHWEIZERBART'SCHE VERLAGSHANDLUNG (E. NAGELE) 1903-5 Q 115 P95 v.5 J. PIERPONT MORGAN PUBLICATION FUND REPORTS OF THE PRINCETON UNIVERSITY EXPEDITIONS TO PATAGONIA 1896- 1899 VOLUME V. MAMMALIA OF THE SANTA CRUZ BEDS I . EDENTATA II. INSECTIVORA III. GLIRES BY WILLIAM B. SCOTT PRINCETON UNIVERSITY PRINCETON, N. J. THE UNIVERSITY STUTTGART SCHWEIZERBART'SCHE VERLAGSHANDLUNG (E. NAGELE) 1903-5 PRESS OF THE NEW ERA PRINTING COMPANY LANCASTER, PA TABLE OF CONTENTS, VOL. V. PAGE INTRODUCTION i MAMMALIA OF THE SANTA CRUZ BEDS ... 3 PART I. EDENTATA 3 DASYPODA 7 TATUIOE 12 Stcgothcrium Amegh. .......... 12 DASYPODID^E ............ 40 Procutatus Amegh. .......... 40 Pareutatus, gen. nov. .......... 68 Prozaedius Amegh. .......... 69 Stenotatus Amegh. .......... 80 PELTEPHILID^E. ............ 88 Peltephilus Amegh. . 88 GENERA INCERT^E SEDIS .......... 104 Pr(zuphi>actus Amegh. ......... 105 Vctelia Amegh. ........... 105 GLYPTODONTIA 107 GLYPTODONTID^E . . . . . . . . . . . 115 Propalaohoplophorus Amegh. . . . . . . . . 115 Cochlops Amegh. .......... 140 Eucinepeltus Amegh. .......... 147 Asterostcmma Amegh. . . . . . . . . . 1 54 ? DCEDICURID-E 156 Mctopotoxus Amegh. . ......... 156 GRAVIGRADA 161 MEGALONYCHID^E ........... 178 Hapalops Amegh. .......... 179 Hyperlcptiis Amegh 261 Eucholoeops Amegh. . . . . . . . . . * . 265 Mcgalonychothcrium, gen. nov. ........ 278 Analcimorphns Amegh. ......... 281 SchismotJierium Amegh. ......... 295 v VI CONTENTS. Pclecyodon Amegh. .......... 3°7 PLANOPSID/E 32° Planops Amegh 322 Prepotheriiim Amegh. . . . . . . . . • • 328 MYLODONTID^; 345 Ncmathcrium Amegh. ......... 34^ Analcitlurium Amegh. . . . . . . . . -357 .EDENTATA INCERT^ SEDIS . . 358 Trematlicrium Amegh. . . . . . . . . . . 358 Adiastaltus Amegh. ........... 359 Plagioccelus Amegh 360 Anathitus Amegh 360 Entdops Amegh 360 RELATIONSHIPS OF THE EDENTATA 361 PART II. INSECTIVORA 365 NECROLESTID^E 365 Necrolcstes Amegh. ........... 365 PART III. GLIRES 384 HYSTRICOMORPHA 389 OCTODONTID.E ............ 389 CAPROMYIN& ........... 389 Neoreomys Amegh 389 Scleromys Amegh. ......... 401 Lomoinys Amegh. . . . . . . . . . 403 Olenopsis Amegh. ......... 404 LONCHERINM ........... 404 Stichomys Amegh. ......... 405 Adelphomys Amegh. ......... 408 Gyrignophus Amegh. ......... 409 Spaniomys Amegh. ......... 409 Graphimys Amegh. . . . . . . . . . 412 ERETHIZONTIDJE ............ 413 ERETHIZONTINM ........... 413 Steiromys Amegh. . . . . . . . . . 413 ACAREMYIN& ........... 421 Sciamys Amegh. .......... 42 1 * Acaremys Amegh. ......... 430 CHINCHILLID/E ............ 433 Perimys Amegh. . . . . . . . . . . 433 CONTENTS. Vll Prolagostomus Amegh. ......... 450 Pliolagostomus Amegh. . . . . . . . . . 458 Stotfttntys Amegh. .......... 459 Sphodromys Amegh. . . . . . . . . . . 459 CAVIID^E ............. 460 Eocardia Amegh. .......... 460 Schistomys Amegh. .......... 479 Phanomys Amegh. .......... 486 GENUS INCERTJE SEDIS .......... 487 Callodontomys ........... 487 BIBLIOGRAPHY 487 ERRATA 490 INDEX 491 DATES OF PUBLICATION OF THE PARTS OF VOLUME V. The dates of issue, as printed on the inside of the covers of the various parts, are approxima- tions made in advance and in each case antedate by a few days the time of actual issue to the sub- scribers. These dates should therefore be corrected as follows : Pp. 1-106. PH. I-XVI, published July 15, 1903. Pp. 107-226. Pll. XVII-XXXV, published November 4, 1903. Pp. 227-364. Pll. XXXVI-LXIII, published September 5, 1904. Pp. 365-499. Pll. LXIV-LXXI, published July 25, 1905. LIST OF TEXT ILLUSTRATIONS. PAGE. Fig. I. Skulls of Santa Cruz armadillos, x f. a, Stegotherium tessdatum ; b, Pro- zaedius exilis ; c, Stenotatus patagonicus ; d, Proeutatus lagena . . -j Fig. 2. Skulls of Santa Cruz armadillos, x f. a, Stegotherium tesselatum ; b, Pro- zaedius exilis ; c, Proeutatus lagena. ....... 9 Fig. 3. Skulls of Santa Cruz armadillos, x f. a, Stegotherium tesselatum; b,Pro- sa'edius exilis ; c, Proeutatus lagena; d, P. cenophorus. . . . . 10 Fig. 4. Right manus of Santa Cruz armadillos, x f . a, Prozaedius exilis ; b, Steno- tatus patagonicus ; c, Proeutatus robustus . . . . . . n Fig. 5. a, Right pes of Stcgotherium tesselatum, x f ; b, left pes of Proeutatus lagena, X f 12 Fig. 6. Pelvis of Stegotherium tesselatum, left side, X f . . . . . . 30 Fig. 7. Pelvis of Stegotherium tesselatum, x f ; a, dorsal view ; b, ventral view. . 3 1 Fig. 8. Upper teeth of glyptodonts, x \. a, Glyptodon asper (after Burmeister) ; b, Propalceohoplophorus aus traits ; c, Eucinepeltus petestatus. . . . 109 Fig. 9. Lower teeth of glyptodonts, x \. a. Glyptodon asper (after Burmeister) ; b, Propalaohoplophorus australis ; c, Eucinepeltus petestatus. . . . 109 Fig. 10. Skulls of glyptodonts, leftside, x \. a, Glyptodon asper (after Burmeister) ; b, Propalaohoplopliorus australis ; c, Eucinepeltus complicatus (mandible from E. petestatus). ........... 1 10 Fig, 1 1 . Skulls of glyptodonts, top view, x \ ; a, Glyptodon asper (after Burmeister) ; b, Propalceohoplophorus australis ; c, Eucinepeltus complicatus. . . . 1 1 1 Fig. 1 2. Bones of left fore-limb of glyptodonts, X \. a, Glyptodon asper (after Bur- meister); b, Propalceohoplophorus australis. . . . . . . 112 Fig. 13.' Bones of the left hind-leg and foot of glyptodonts, x \. a, Glyptodon asper (after Burmeister) ; b, PropalceohoplopJwrus australis. . . . . 114 Fig. 14. Upper teeth of Santa Cruz Gravigrada, x ^. a, Hapalops indiffcrens ; b, H. elongatus; c, Megalonychotherium atavus ; d, Analcimorphus gigantcus ; e, Schismotherium splendens ; f, Pelecyodon cristatus ; g, Hype rleptus garzoni- anus ; h, Planops magnus. . . . . . . . . . 162 Fig. 15. Lower teeth of Santa Cruz Gravigrada, x \. a, Hapalops longiceps ; b, H. indiffcrens; c, H. elongatus ; d, Eucliolccops fronto ; e, Pelecyodon arcuatus ; f, Prepotherium moyani ; g, Ncmatherium angulatum (marked N. sp.). . 163 Fig. 1 6. Skulls of Santa Cruz Gravigrada, x \. a, Hapalops longiceps ; b, H. elonga- tus ; c, Megalonychotherium atavus ; d, Analcimorphus giganteus ; e, Schis- motherium splendens ; f, Pelecyodon cristatus ; g, Planops magnus . . 164 1 Erroneously marked Fig. 3 in the text. ix X LIST OF TEXT ILLUSTRATIONS. Fig. 17. Skulls of Santa Cruz Gravigrada, top view, x £. a, Hapalops longiceps ; b, ff. ructimeycri ; c, Megalonychothcrium atavus ; d, EucJwlaeops fronto ; e, Analcimorphus giganteus ; /, Schismothctium fractum ; g, S. splendens ; //, Planops magnus . . . . . . . . . . . 165 Fig. 1 8. Occiputs of Santa Cruz Gravjgrada, x \. a, Hapalops longiceps ; b, Eucholoe- ops fronto ; c, Hapalops dongatus ; d, Pelecyodon cristatus . . . . 166 Fig. 19. Mandibles of Santa Cruz Gravigrada, x £. a, Hapalops indifferent ; b, H. rostratus ; c,H. elongatus ; d, Eucholceops fronto ; e, Schismotherium fractum (marked S. spletidens f) ; /, Prepotlicrium moyani ; g, Ncmatherium angula- tum (marked N. sp.) .......... 167 Fig. 20. ? Hapalops sp. Right scapula, x \ . . . . . . . . 169 Fig. 21. Hapalops ructimeycri, pelvis from the ventral and right sides, x \ . . . 170 Fig. 22. Humeri of Santa Cruz Gravigrada, x \. a, Hapalops longiceps ; b, H. ructi- meycri; c, Pelecyodon arcuatus ; d, f Nematherium sp. . . . . 171 Fig. 23. Hapalops longiceps, a, left ulna, x \. b, left radius, x \ . . . . 172 Fig. 24. Hapalops longiceps, left manus, x \ . . . . . . . 172 Fig. 25. Bones of the hind limb of Santa Cruz Gravigrada, x \. a, Hapalops (femur of H. elongatus, tibia and fibula of H. longiceps); b, Analcimorphus giganteus (marked A. leptocephalus) ; c, Prepotherium potcns . . . . . 173 Fig. 26. Pes of Santa Cruz Gravigrada, x \. a, Hapalops longiceps ; b, Analci- morphus giganteus (marked A. leptoccphalus) ; c, Pelecyodon arcuatus . . 1 74 Fig. 27. Dorsal side of right astragalus, nat. size, a, Hapalops elongatus ; b, Prepo- therium potens . . . • . . . . . . . . 175 Fig. 28. Distal end of right calcaneum, nat. size, a, Hapalops elongatus ; b, Prepo- therium potcns ........... 176 Fig. 29. Type of Hapalops rectangularis, x \. La Plata Museum .... 206 Fig. 30. Type of Hapalops ellipticus, x \. La Plata Museum ..... 206 Fig. 31. Type of Hapalop s indifferens, x {. La Plata Museum 208 Fig. 31. Type of Hapalops (Tapinothcriuni) aguirrei, x f . La Plata Museum . . 213 Fig. 32. Type of Hapalops aguirrei, x f. La Plata Museum . . . . . 214 Fig. 33. Eucholceops ciirtus, type, x \. Ameghino collection ..... 277 Fig. 34. Euchoteops curtus, type, x \. Ameghino collection ..... 277 Fig- 35- Schismotherium fractum, mandible, x \. Ameghino collection . . . 302 Fig. 36. Schismotherium fractum, left manus, x \. Ameghino collection . . . 302 Fig. 37. Pelecyodon cristatus, mandible, x \. Ameghino collection .... 309 Fig. 38. Ncmatherium sp., left astragalus and left calcaneum, x \. Ameghino collection ............ 350 Fig. 35.' Phalanges of digit III., left manus of Necrolcstes patagonensis, x \. a, from ulnar side ; b, from dorsal side . . . . . . . . 376 Fig. 36.' Femur of Necrolcstes patagonensis, x \ . a, front view ; b, rear view . . 377 F'g- 37-' Grinding teeth of Myocastor coypus, crown view, x \. a, right upper teeth ; b, right lower teeth 390 Fig. 38.' Skulls of Octodontidae, side view, a, Myocastor coypus, x § ; b, Capromys fournieri, x \ ; c, Ncorcomys australis, x f . . . . . . 391 1 Through an oversight these numbers have been duplicated. LIST OF TEXT ILLUSTRATIONS. xi Fig. 39. Skulls of Octodontidse, top view, a, Myocastor coypus, x f ; b, Capromys four- nicri, x \ ; c, Ncorcomys australis, x \ . . . . . . 393 Fig. 40. Grinding teeth of Viscaccia chilensis, crown view, x \. a, right upper teeth ; b, right lower teeth .......... 434 Fig. 41. Skull of Viscaccia chilensis, x \. a, left side; b, top . . . . . 435 Fig. 42. Type of Prolagostomus obliquidcns ; mandible, crown view, x 2 . . . 456 Fig. 43. Grinding teeth of Caviidas. a, right upper teeth ; a', right lower teeth of Doli- clwtis magellanica, x \ ', b, right upper teeth ; b1 ', right lower teeth of Cavia cobaya, x \ 461 Fig. 44. Eocardia sp., teeth of young individuals, lower right side, external and crown views, x \ . a, Dpf in very young stage ; b, Dp3, mT and ^, later stage. A. M. N. H 462 Fig. 45. Skulls of Caviidse, leftside, a, Dolichotis magellanica, x \ ; b, Cavia cobaya, X \ ', Eocardia cxcavata, x \ . . . . . . . . 464 Fig. 46. Eocardia montana, lower grinding teeth, x \. a, right side, crown view ; b, right side, external and crown views, A. M. N. H. ; c, left side, crown view, A. M. N. H 473 Fig. 47. Eocardia excavata, lower grinding teeth, external and crown views, x \. a, right side ; b, left side of same individual (No. 15,211) . . . . 475 Fig. 48. Eocardia modica, left lower grinding teeth, external and crown views, x \ . A. M. N. H 476 Fig. 49. Type of Eocardia petersoni, left mandibular ramus, crown view, x \ . 477 MAMMALIA OF THE SANTA CRUZ BEDS. PART I. EDENTATA. / BY WILLIAM B. SCOTT, PRINCETON UNIVERSITY. INTRODUCTION. FROM many points of view the fossil mammals of the Santa Cruz formation are of remarkable interest. They present a number of unusually instructive phylogenetic series and throw much welcome light upon the manner in which the evolution of the Mammalia has been accomplished. Further, they bring up questions of profound and far- reaching importance, concerning their relationships to the animals of the northern hemisphere, as well as to those of Africa and Australia. With these questions are connected the problems of geographical distribution and of the migrations of land animals, the former extent and connections of the continents, in brief, the whole mystery of the southern hemisphere. The able writings of Dr. F. Ameghino have directed the attention of palaeontologists to these and kindred questions, but, unfortunately, this wonderful Santa Cruz fauna has hitherto been but scantily represented in the museums of Europe and North America, and, in consequence, stu- dents of the Mammalia could gain only a very imperfect knowledge of these animals from brief diagnoses and inadequate illustrations. In order, therefore, to render the material useful to those who cannot examine the originals, an otherwise unnecessarily minute prolixity of description and fulness of illustration have seemed to be called for. This course is further made advisable by the extraordinary variability of many of these mammalian groups, which renders the usual systematic treatment so un- satisfactory when applied to them. 2 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. It has been my privilege to study all of the principal collections of Santa Cruz fossils, including almost all of the types. These collections are, in addition to the one at Princeton, those of the American Museum of Nat- ural History, New York, the Munich Museum, the British Museum, the La Plata Museum, and, most important of all, the private collection of Dr. F. Ameghino. Abundant use has been made of the free permission accorded me to figure and describe such material as suited my purpose. As this volume may fall into the hands of some who will have no op- portunity or occasion to consult Volume I of these Reports, it will not be superfluous to repeat here a number of statements from the general edi- torial preface. In the spring of 1901 the writer found it necessary " to visit the Mu- seums of La Plata and Buenos Aires and study the collections there gath- ered. He is glad of this opportunity to express his feelings of profound gratitude to those who did everything in their power to render these investigations helpful and satisfactory. "Dr. Florentine Ameghino, now director of the National Museum at Buenos Aires, but then living in La Plata, permitted the freest possible use of his great private collection of Patagonian fossils, a collection which is especially valuable because it contains by far the largest number of the type specimens of the genera and species named from Patagonian horizons. "Dr. F. P. Moreno, Director of the La Plata Museum, . . . placed his museum and all its resources unreservedly at the disposal of the visitor, who, living in the building for several months, enjoyed its hospitality in the most literal sense of the word. The Secretary of the Museum, Sr. R. Catani, and the Curators, Dr. Santiago Roth, Professor R. Hauthal, Dr. R. Lehmann-Nitsche and Sr. Carlos Bruch, were indefatigable in their assistance, and most hearty thanks are due to each and all of them for countless instances of helpful kindness." In addition, I wish to express my cordial thanks to my friend, Pro- fessor H. F. Osborn, who has given me unrestricted use of the fine col- lection of Santa Cruz fossils, made for the American Museum of Natural History by Mr. Barnum Brown. This collection admirably supplements that made by Messrs. Hatcher and Peterson for the Museum of Princeton University. How extensively this collection has been employed will be apparent from the plates. EDENTATA OF THE SANTA CRUZ BEDS. 3 Finally, I must make grateful and appreciative mention of the help rendered by my assistant, Dr. Marcus S. Farr, by Mr. Jacob Geismar, preparator, and by Mr. F. van Iterson, artist, who have labored with un- wearied zeal and without whose assistance the work could hardly have been undertaken. EDENTATA OF THE SANTA CRUZ BEDS. Following the suggestion of Oldfield Thomas ('87, p. 459) the Edentata will be here regarded as forming a separate subclass of the mammals, and in what follows no account will be taken of the so-called edentates of the Old World, the position of which is altogether uncertain. Discussion of the systematic position of the subclass, as a whole, and of the mutual relationships of its various subdivisions will be deferred until a detailed account of the Santa Cruz representatives of the group shall have been laid before the reader. It is my purpose in the present section merely to consider the more salient characteristics of the fossils. The following table gives the scheme of classification here adopted. I. DASYPODA. 1 . Tatuidce. 2. Dasypodidce. 3. Chlamydophoridce. 4. Peltephilidcz. II. GLYPTODONTIA. 1. Sclerocalyptidce. 2. Glyptodontidce. 3. Dcedicuridce. III. GRAVIGRADA. 1. Megalony chides. 2. Megatheriidce. 3. Mylodontidce. IV. TARDIGRADA. 1. Bradypodidce. 2. Cholccpidce. V. VERMILINGUIA. i. Myrmecophagidce. 4 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. In the Santa Cruz fauna the edentates form one of the most conspicuous elements, both in the abundance of individuals and in the number and variety of the genera and species. As a whole, they are strikingly dif- ferent from those of recent times, for of the three orders which are repre- sented among the fossils, armadillos, glyptodonts and ground-sloths, only the first-named persists to the present day, the other two being extinct- On the other hand, no trace has yet been found in the Santa Cruz beds of the true sloths or of the anteaters. It can hardly be doubted that both of these orders had already become differentiated and were in existence as such. If so, however, they must have originated in some other part of the South American continent and were prevented by climatic, or other barriers from extending their range into Patagonia. One fact which clearly justifies this assumption is the relatively small degree of structural change that took place between the edentates of the Santa Cruz and those of later periods, such as the Pampean. There are many differences of detail between the earlier and the later forms, but nothing comparable to what would be implied in the derivation of the sloths or anteaters from any known Santa Cruz fossils. As will be shown more at length in a later section, much the same statement applies to the armadillos of the Santa Cruz beds, with reference to their connection with those of modern times. Speaking broadly, the latter would appear not to have been derived from the former, which sug- gests that Miocene Patagonia was rather an outpost of the South Ameri- can fauna than the main area of its development. The Santa Cruz glyptodonts are, on the whole, markedly more primi- tive than those of the Pampean and in many structural details show a closer connection with the armadillos than do the latter, but, for the most part, the Santa Cruz genera do not appear to be directly ancestral to those of the Pampean. Like the armadillos, they seem to be aside from the main lines of descent which terminated in the giant types of the Pleisto- cene. On the other hand, the Gravigrada appear to be more directly ancestral to the great Pampean forms, and representatives, if not the actual ances- tors, of almost all the later genera may be observed in this fauna. How- ever, no entirely convincing solution of these problems can be obtained until the fossils intermediate in time between the Santa Cruz and the Pampean are more fully known. EDENTATA OF THE SANTA CRUZ BEDS. 5 A remarkable feature of the Santa Cruz edentates is their variability within certain well-defined limits. As a rule, the genera may be readily identified, but the species, especially of the Glyptodontia and Gravigrada, present extraordinary difficulties to the systematist. This variability, how- ever, confines itself to comparatively unimportant details, and the character- istics of the three orders and of the families and genera within those orders are already, for the most part, firmly established, though transitional forms from species to species and, less commonly, from genus to genus abound. • i. The Santa Cruz edentates are relatively small animals and a few of them are really minute. As compared with the ground-sloths and glypto- donts of the Pampean, they are pygmies, but the armadillos have a greater number of large species than exist at present, though none of them is gigantic, or comparable to such a form as Macroeuphractus. 2. Fully developed carapaces are found in all of the armadillos and glyptodonts of the period, but, as yet, no dermal ossifications have been found in connection with any of the ground-sloths. This is the less surprising, because very little is known of the skeleton of the Santa Cruz Mylodontidce, the only family in which these ossifications could be expected to occur. 3. The teeth are in all cases devoid of enamel, rootless and tubular, though they may be lobate, examples of which occur in all three of the orders. No trace of a milk-dentition has been observed. Premaxillary teeth and the corresponding mandibular teeth have been definitely found only in the armadillos, though rudimentary traces of such teeth are ap- parent in some of the glyptodonts and they may also occur in a few of the ground-sloths. 4. The skull has few common features throughout the series, each order having its own characteristic type of structure. The difference is largely in the relative development of the cranial and facial regions, which varies from the extremely elongate skull, with long, slender rostrum, of the arma- dillos, to the short, broad, deep and almost cubical skull of the glypto- donts. Sagittal and occipital crests are never very strongly marked, but they are present in most genera of all three orders and there is no such development of cranial air-sinuses as took place at a later period. In all of the known genera from this formation except Peltephilus there is a more or less prominent descending, suborbital process given off from the zygomatic arch ; it may be formed by the jugal alone or by the jugal and 6 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. maxillary, and in position it may be at the anterior or the posterior end, or in the middle of the arch. The arch itself is always complete, never rudimentary, though in the Gravigrada the jugal is usually loosely attached and has been lost from most of the specimens. 5. The neck has never more or less than seven vertebra, though in all of the armadillos and glyptodonts the apparent number is much reduced by coossification. In the same two groups the trunk is short and the number of trunk-vertebrae small and in the glyptodonts these vertebras are coossified into long "tubes," one thoracic, the other lumbo-sacral. In the Gravigrada, on the contrary, the trunk is very long and the trunk- vertebrae numerous. In both armadillos and ground-sloths the lumbar and posterior thoracic vertebrae have very complex accessory zygapoph- yses, which in the former are as fully developed as at the present time, but in the latter are somewhat less so than they became at a later period. The sacrum may be long (Dasypoda, Glyptodontia) or short (Gravigrada) but always articulates with both ilia and ischia. The tail is sometimes of moderate length and sometimes very long, but is always heavy and always has a complete series of chevron-bones. 6. The limbs and feet differ greatly in the three orders and have com- paratively little in common. The scapula is broad and has an ex- tremely prominent spine and acromion ; the coracoid is very large in the ground-sloths, reduced in the glyptodonts and armadillos, except Pelte- pliiliis. In all three orders the humerus has a similar general appearance, having small tuberosities, extremely prominent deltoid and supinator ridges and internal epicondyle, while the foramen is large. Ulna and radius are separate and, except in the ground-sloths, the former has a very large olecranon. All the carpals are free, but no genus has been found which has the centrale. The manus is pentadactyl and plantigrade, though it is not improbable that the Gravigrada had already begun to rest the ulnar edge of the hand upon the ground ; the metacarpals are free and, except in one species of armadillo, none of the phalanges are coossi- fied. The unguals are generally longer and more pointed than in the pes. The pelvis [differs much in the three groups, but the ischia are always extensively connected with the sacrum. The femur is long and has prom- inent trochanters and in some of the armadillos the great trochanter reaches extraordinary proportions. Tibia and fibula are free in the Gravi- grada, coalesced at both ends in the glyptodonts and armadillos. The EDENTATA OF THE SANTA CRUZ BEDS. 7 pes is pentadactyl and, except in the glyptodonts, is plantigrade, while in the latter group it is semidigi'tigrade. No coossification occurs in tarsus, metatarsus or phalanges, and the unguals, which in the ground-sloths are large claws, in the other two orders are more or less hoof-like, completely so in the glyptodonts. DASYPODA. The Santa Cruz armadillos form a peculiar assemblage of types, very unlike, as a whole, the modern representatives of the suborder, for only one, or possibly two, species would appear to be directly ancestral to ex- isting forms, while the majority belong to extinct lines. Some of these lines, like that of Proeutatus, for example, persisted till a much later per- iod than the Santa Cruz, and reached their culmination in the Pampean, but have no representatives in the recent fauna, while other series, like FIG. i. Skulls of Santa Cruz armadillos, x f . a, Stegotlurium tcsselatum ; b, Prozaedius exilis ; c, Stenotatus patagonicus ; d, Procntatus lagcita. Stegotlierium and the extraordinary PeltepJiilus, are not known to pass be- yond the limits of the Santa Cruz formation. At the same time, there is a very notable diversity among these armadillos and no less than* three families and seven genera have been described, most of the genera hav- 8 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. ing each several species. The discovery of more complete material may reduce these numbers, but the variety will continue to be remarkable. Attention has already been called to the difference between the Santa Cruz and the recent armadillos, a difference which can be made clear in a few words. No probable forerunner of Dasypus, Priodoiites, Tolypeiites, CJilamydoplionis, or Tatu, has been found in these beds, though some one of the species of Prozaedius was almost certainly an ancestor: of the recent Zacdyus, and it is possible, though far from certain, that some species of Stenotatns stood in the same relation to the modern Cabassous. In view of the stage of differentiation attained by the Santa Cruz armadillos, it is most improbable that all of these modern types should have originated since that period. This confirms the conclusion indicated by several other mammalian series, that in Miocene times Patagonia was not the principal theatre of evolution of the South American fauna. This would explain the entire absence from the Santa Cruz beds of many types which would naturally be expected to occur there. In general, the armadillos of this period may be said to have attained nearly the modern degree of specialization, though, in many details, prim- itive characteristics have been retained. As Ameghino has pointed out, ('94, 178) the carapace never has an anterior buckler, but is made up of movable, imbricating bands, except posteriorly, where a larger or smaller number of plates are joined together by their edges to make the pelvic buckler. In one genus, Prcetiphractus, (fide Ameghino) there is no pelvic buckler, all the plates being movable, and it is uncertain whether this was not also true of Stegotherium. In Peltephilus the pelvic buckler would appear to have been very loosely formed, the plates merely touching one another, though in this region they are not imbricating. The cephalic shield is usually composed of numerous small, non-imbricating, irregu- larly polygonal and rather heavy plates, which are finely pitted and dis- play no regular sculptural pattern, but in the altogether exceptional genus Peltephilus these plates are large, very thick and coarsely sculp- tured. A further remarkable peculiarity of the head-shield in this genus is the presence of one or two pairs of pointed, horn-Jike scutes upon the rostrum. It is a curious fact that no plates of the tail-sheath have been found in association with any of the genera, except Peltephilus. It seems most 'unlikely that all the other genera had unarmored tails and yet, in view of the large number of well-preserved specimens, including the EDENTATA OF THE SANTA CRUZ BEDS. 9 caudal vertebras, that have been collected, it is possible that such may have been the case. Considerable variety is displayed in the dentition, though in no species has any trace of enamel or of the milk-teeth been observed. The marked diphyodontism of the modern Tain makes this fact somewhat surprising. Premaxillary teeth and the corresponding mandibular teeth occur in two genera, Proeutatus and Peltephilus, and in the latter they are so closely approximated that the teeth of both upper and lower jaws form a continu- ous series. Prosaedius and Stenotatus have teeth like those of most recent FIG. 2. Skulls of Santa Cruz armadillos, x f . a, Stegothcriitm tesselatiim ; b, Prozaedius exilis ; c, Proeutatus lagena. armadillos, while in Proeutatus the teeth show an incipient division into lobes and have a complex masticating surface, produced by layers of dentine of different hardness and color, and with some resemblance to the teeth of the glyptodonts. In Peltepliihts the teeth are sharply pointed and form what appears to have been a formidable lacerating apparatus, while, finally, in Stegotherium the dentition is in such an extreme state of reduction that the animal must have been functionally all but edentulous. In all the known genera, except Peltephilus, the skull has a very elongate and usually a slender rostrum, and, with the same exception, the zygomatic arch has a prominent descending, suborbital process, which is 10 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. generally from the jugal, but sometimes from the zygomatic process of the maxillary also. The cervical vertebrae closely resemble those of the modern armadillos, one or two vertebrae coalescing with the axis. The trunk is short and in those genera in which the number is known does not contain more than eleven thoracic and four lumbar vertebrae ; in the lumbar and the posterior part of the thoracic regions, the vertebrae have the same complex mode of articulation, by means of accessory zygapophyses, as is found in recent genera. The sacrum is long and always has an extensive union with the FIG. 3. Skulls of Santa Cruz armadillos, x f . a, Stegotherium tcssclatum ; b, Prozaedius exilis ; c, Proeutatus lagena ; d, mandible of P. cenophorus, crown view of right ramus. ischia. The tail varies considerably in the different genera ; it is usually quite elongated, but in some of the genera, as Proeutatus, it is of only moderate length, though very heavy ; in Stegotherium the caudal vertebrae are remarkable for the great development of their transverse processes. The ribs, both costal and sternal, and the sternum differ in no important respect from those of the recent armadillos. The shoulder-girdle is practically the same as in the existing genera, but the humerus is noteworthy for the great size and prominence of the deltoid ridge, and the epicondylar foramen is always present. The ulna has a very large olecranon, which in most of the species terminates proxi- EDENTATA OF THE SANTA CRUZ BEDS. II mally in a prominent, incurved hook. The manus is always pentadactyl and all the digits bear claws ; in all known species the second digit is the longest of the series. In only one genus, Stenotatus, are any of the phalanges coossified. The lingual phalanges are always long, heavy, decurved and pointed, and were evidently well adapted to burrowing habits. The pelvis varies considerably in the different genera, but does not depart widely from the modern type. The femur is elongate and has a IV II! 'in FIG. 4. Right manus of Santa Cruz armadillos, x f . a, Prozaedius exilis ; b, Stenotatus patagonicus ; c, Proeutatus robustus. very prominent great trochanter, which in Proeutatus reaches remarkable proportions, the third trochanter is. also well developed in all cases. As in the recent armadillos, the tibia and fibula are invariably coossified at both the proximal and the distal ends. Like the manus, the pes is always pentadactyl, though in some of the genera, and especially in Peltephilus, the lateral digits are much reduced. The ungual phalanges are usually much shorter and broader than those of the manus and are often more like hoofs than claws. In size, there is much variety among the Santa Cruz armadillos, rang- ing from the minute Prozaedius to Proeutatus, some species of which are larger than any existing armadillo, except Priodontes, while the very incompletely known Peltephilus grandis may have equalled or even sur- passed the latter. 12 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. To sum up : The Santa Cruz armadillos differ comparatively little in appearance or in structure from the modern ones, and yet it is apparent that they do not, as a whole, represent the main line of descent which IV FIG. 5. a, Right pes of Stegotherium tesselatum, x f ; b, left pes of Procutatus lagena, x |. ended in the recent genera. That evolution must have taken place in some other region of the South American continent, doubtless the same region as that which gave rise to the true sloths and the anteaters. TATUID^. STEGOTHERIUM Ameghino. (Plates I-IV.) Stegotherium Amegh. ; Enumeracion sistematica de Mam. Fos. de Pata- gonia, 1887, p. 25. Scotceops Amegh. ; Ibid., p. 25. Peltephihis Lydekker, in part; Anales del Museo de La Plata, 1894, T. Ill, p. 67. In Ameghino's first paper on the Santa Cruz fauna ('87$) he named two genera of edentates, which seemed to have nothing in common. One of these, Scotceops, was described from a fragment of the mandible, which included the alveoli of two teeth and a part of the ascending ramus. The second genus, Stegotherium, was founded upon a number of isolated f EDENTATA OF THE SANTA CRUZ BEDS. 13 scutes of the carapace, of quite peculiar type. In a subsequent publica- tion ('94«) the former was referred to the Monotremata, while the latter was regarded as most nearly allied to Peltepkilus. Until the collections made by Messrs. Hatcher and Peterson, no additional specimens of these extraordinary animals, other than scattered plates of the carapace, had been obtained. On examining the drawings and notes which I had taken with me to La Plata, Dr. Ameghino at once expressed the belief that these two supposedly different genera were really one and the same, a belief which has been abundantly confirmed by the material in the Princeton collection. In his last paper on the subject ('02, p. 65) the original de- scriber has formally retained the name Stegotherimn and treated Scotceops as a synonym. In the Princeton collection the genus is represented by two specimens which seem referable to S. tesselatum, for though they may possibly rep- resent two different species, the differences between them are more prob- ably due to individual variation. Of these specimens, one (No. 15,566) comprises the greater part of the carapace, about half of the skull, the atlas, the compound cervical, seven thoracic and four lumbar vertebrae, the sacrum and all of the caudal vertebras, save the three or four terminal ones, together with two ribs, the scapula, humerus, pelvis, femur, tibia and fibula. The second specimen (No. 15,565) has the anterior portion of the carapace, the skull complete, the neck except the sixth and seventh cervi- cals, two thoracic vertebras, and the right pes. Carapace. — The carapace differs quite markedly from that of any other known Santa Cruz genus. I am unable to say whether a pelvic buckler was formed or not, but it is clear that there was no anterior buckler, and in one of the specimens twenty movable bands may be counted in position (Plate I). In the anterior region the scutes are smaller and thicker, and their exposed portions have a more nearly square outline than those of the middle region ; in longitudinal section these scutes are lozenge-shaped, with long diameter in the fore-and-aft direction and with no notable dif- ference in thickness between the exposed and covered portions of the plates. Indeed, in this region there is but a partial imbrication of the plates and the mobility of the bands must have been relatively slight ; only a small change in the character of the plates would be needed to convert this portion of the carapace into a fixed scapular shield. In the middle region of the carapace the plates are much elongated, becoming 14 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. nearly three times as long as they are wide,- and each scute is clearly demarcated into covered and exposed portions. The anterior, covered portion occupies somewhat less than one half of the length of the plate ; it is considerably thicker than the exposed portion and, on the dorsal side, the line of junction between the two is marked by the abrupt, step-like descent which is usual in the armadillos. Though the small, square plates of the anterior region of the carapace are thus markedly different from the narrow, elongate plates of the middle region, there is no abrupt change, such as occurs in the genera having a definite scapular buckler, but a gradual transition from one to the other. The sculpture of the exposed portion of the scutes is very characteristic ; the pattern consists of a very low and narrow, but quite sharp, median, longitudinal ridge, which usually pursues an oblique course, and of raised lateral borders, while the whole exposed surface is finely pitted, or granu- lar. Near the line of junction between the exposed and the covered part of the scute is a transverse row of large and conspicuous piliferous pits, which are of somewhat irregular size and shape, the median one usually being larger than the others. The lateral and posterior borders of the plate are also pitted in an almost continuous line, though these pits are much smaller than those of the anterior transverse row. The appearance of the plates seems to indicate that the animal was in life quite thickly clothed with hair. Dentition.- -The teeth, which are of minute size, are of somewhat vari- able number, even on the two sides of the same skull, and combining the two specimens, we get the formula |=|. These teeth are of cylindrical shape and together occupy but a short space in the hinder portion of the jaws, leaving much the greater portion of the latter entirely edentulous. They are not, as in most armadillos, so bevelled by wear as to have a transverse, median ridge, but are worn obliquely from within outward. So extreme is the reduction of the teeth that they can hardly have had any functional importance. Skull (Plate II.) — On the whole, the skull has more resemblance to that of Tatu than to that of any other existing armadillo, though the elonga- tion of the rostrum and the great attenuation of the jaws produce a certain likeness to Priodontes. The cranium is short, broad and high, the face long, slender and tapering, the extremely slender mandible adding but little to the vertical diameter of the face. When viewed from the side, the EDENTATA OF THE SANTA CRUZ BEDS. 15 upper profile of the skull descends forward very gradually and almost un- interruptedly from the occipital crest to the tip of the rostrum, but is made slightly sinuous by the projection of the frontal sinuses, the posterior con- vexity of the nasals and the upturning of the end of the rostrum. In one of the specimens (No. 15,566) the frontal sinuses are very inconspicuous externally, making this portion of the profile somewhat concave. In Tatu the upper contour of the skull is quite similar, though modified by the great development of the frontal sinuses and the maxillary antra. The occiput is high and inclined forward slightly, broad at the base, con- tracting regularly and gradually to the top, resembling the occiput of Tatu in shape, but is less square in outline, being broader ventrally and nar- rower dorsally. As a whole, the occipital surface is convex transversely and, in addition, the upper half displays three vertical ridges, of which the median one, for the vermis of the cerebellum, is the most prominent, though decidedly less so than in the recent genus. The lambdoidal crest is almost obsolete, except near the dorsal summit, where it is quite thick and prominent and is emarginated by a broad, rectangular notch, at the bottom of which are two small but very deep, hemispherical fossae. In Tatu a similar, but much less distinct notch is present, while the fossae are almost obsolete. The foramen magnum is low and wide and, though relatively higher than in the modern genus, is more like that in the latter than that of Dasypus, being to a large extent formed by a broad, deep, V-shaped notch of the basioccipital between the condyles. The bones of the occiput are so completely fused together that their limits cannot be determined with certainty, but they seem to have quite similar proportions to those of Tatu. The basioccipital is short and broad, much wider posteriorly than anteriorly, as it" expands behind the tympanic and periotic, much as in the last named genus ; it is convex transversely — has a low, curved transverse ridge, which is separated by a shallow groove from the margin of the foramen magnum. In one of the specimens there is a faintly marked median keel. On each side of what is probably the line of suture with the basisphenoid, is a prominent, pitted tubercle, doubtless for the recti antici tendons. The posterior part of the basioccipital is bent downward at an obtuse angle, somewhat as in Tatu, but more abruptly, and is thicker and more rounded. The exoccipitals are broader than in the modern genus and are so extended that very little of the squamosal is visible from behind, while in Tatu much of this bone is 1 6 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. so visible. This is one of the few characters in which Stegotheriuui is more like Dasypns. The condyles are widely separated and very oblique, rising toward the outer sides; they are less completely sessile than in Tain, being demarcated from the occipital plane by deeper fossae, and on the ventral side are much more distinctly separated from the body of the basioccipital. In shape, they are transverse semicylinders ; the condylar elevation extends out laterally to the borders of the occiput, where it is separated from the squamosal only by a very narrow strip of the periotic, but the articular surface does not extend so far, and is quite deeply invaded by a lateral sulcus ; the ventral portion of the surface is produced farther laterally than the dorsal part. There is no paroccipital process nor any space for such a process between the condylar ridge and the periotic. Though the sutures between the supraoccipital and the exoccipitals have disappeared, it may reasonably be assumed that, as in Tatu, the former was very large, making up nearly the whole of the occipital surface, and forming the dorsal margin of the foramen magnum and the whole of the lambdoidal crest ; a small portion of the bone is bent over upon the roof of the cranium, though less conspicuously so than in Tatu, owing to the depth of the median notch. The periotic is exposed as a narrow strip between the exoccipital and the squamosal ; it has about the same relative breadth as in Tatu and is perforated by a similar vascular foramen as in the latter, but has no such groove leading into it. Just above the outer edge of the condylar eleva- tion is a small but deep depression in the periotic, which is not present in the modern genus. The mastoid process is short, but distinct, and is closely applied to the posttympanic process of the squamosal ; distally it ends in a concavity for the hyoid. The auditory, or petrosal, portion of the periotic is quite large and very superficial in position and is not en- tirely concealed from view by the tympanic. The latter is small and forms an incomplete ring of bone, C-shaped when viewed from the ven- tral side ; it is almost exactly like that of Tatu, but is a little broader, covering more of the periotic. The basisphenoid, though short and broad, is somewhat longer than the basioccipital and narrows forward slightly ; it has a raised line near each lateral border, and these lines converge anteriorly, enclosing a shield- shaped area, with a shallow fossa on each side of the median line, thus giving to the whole bone a very different appearance from the simply EDENTATA OF THE SANTA CRUZ BEDS. 17 convex form seen in Tatu. The presphenoid is quite long and broad, very thin and of nearly uniform width, so far as it is exposed in the roof of the posterior nares. The alisphenoid is small and is perforated by the foramen ovale, while its anterior edge forms the hinder border of the fora- men rotundum ; the descending process is very short. The orbitosphenoid seems to be somewhat larger, but the limits of the bone are hardly deter- minable, as both skulls are injured in this region. The parietals are short and broad, descending farther upon the sides of the cranium than in Tatu ; they form no sagittal crest, but only a narrow sagittal area, which widens anteriorly to the frontal suture, and is clearly demarcated from the temporal fossae by being raised well above them. In Tatu this area is broader, but is very obscurely marked, while in the fossil it is conspicuous, as it is not only raised, but its smoothness is in decided contrast to the roughened surface of the remainder of the parietals. Except near the anterior border, the sagittal area is much thickened and filled with cancellous bone. The squamosal is a large bone, lower, but longer than the parietal, so that it has a considerable connection with the frontal ; the suture with the exoccipital is very short, the squamosal touching that bone by hardly more than a corner, though it has a long suture with the mastoid portion of the periotic, and it takes no share in the formation of the lambdoidal crest. The auditory meatus makes a broad, deep notch in the squamosal. A deep groove extends upon the side of the latter, its ventral and pos- terior border being formed by a prolongation of the dorsal border of the zygomatic process, though this border is much less elevated than in Tatu. The glenoid cavity is altogether different from that of the modern genus, being a narrow, elongate, longitudinal groove, with no trace of a post^- glenoid process, and resembling that of a rodent rather than that of an armadillo. In Tatu, on the other hand, this surface is elevated, square, and nearly plane, and the postglenoid process, though much reduced, is yet distinctly present. The zygomatic process is extremely short, almost as short as in Tatu ; it is a shelf-like projection with raised external border which, however, is not nearly so elevated as in the recent genus ; the jugal covers it so that only a small tongue of the bone is externally visible. The jugal is quite long, forming nearly the whole of the zygomatic arch and is very different in shape from that of any existing armadillo ; its 1 8 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. anterior portion, which has a very short contact with the maxillary and an extensive one with the lachrymal, is slender and compressed, but with prominent and somewhat flaring suborbital border ; posteriorly it gives off a large, vertical plate of bone, with much thickened and rugose hinder border ; this plate extends as far as the posterior edge of the zygomatic process and recalls the process seen in the sloths and glyptodonts, but is placed much farther back and is postorbital rather than suborbital. The dorsal border of the jugal is almost straight, rising gradually to the junction with the lachrymal, while the ventral border has a steep inclination down- ward and backward. As a whole, the zygomatic arch is relatively longer than in Tatn and is much less decurved to form the suborbital border ; the jugal makes up a considerably larger share of the arch, extending farther both forward and backward. The arch also curves outward less from the side of the skull, enclosing a longer and narrower temporal fossa, a dif- ference which is increased by the shallower postorbital constriction. The lachrymal is quite large, though relatively rather less so than in Tatzt, and less extended posteriorly than in the latter ; this posterior ex- tension is slender and apparently solid, while in the modern genus it is so inflated as to have a hollow appearance. The facial surface of the lachrymal is convex but has not such a swollen appearance, nor is it inflected so far into the orbit, as in Tatu ; it is also less quadrate in shape and ends anteriorly in a point, which is inserted between the frontal and maxillary. The lachrymal foramen is larger and placed more in advance of the orbit than in the existing genus, and behind the foramen is a deep pit, or groove, leading into it, which is wanting in the latter. Although the frontals are very long and, as in Tatu, more than twice as long as the parietals, they form relatively little of the cerebral fossa, the postorbital constriction being but little forward of the coronal suture. This constriction is shallower than in the recent genus, and the expansion of the forehead in front of it is less abrupt. The sagittal area is con- tinued forward upon the frontals, ending in ill-defined temporal ridges. On each side of the sagittal area the posterior part of the frontals is somewhat rugose, elsewhere they have a dense and smooth surface. The forehead is quite different from that of Tatn, in which it is vaulted by the great development of the frontal sinuses, while in the fossil the two moderate convexities are separated by a median depression. In one of the skulls (No. 15,565) these convexities are distinct and in the other EDENTATA OF THE SANTA CRUZ BEDS. 1 9 (No. 15,566) they are hardly noticeable. Owing to the less inflated form of the forehead, the descent to the rostrum is less abrupt than in the recent genus. Anteriorly, the frontals are quite deeply notched to receive the narrow nasals, and there are long, pointed nasal processes. The nasals are very elongate, much more so than in Tatu, but other- wise of quite similar shape. Narrow posteriorly, they broaden forward, until near the anterior end they cover the whole width of the rostrum and curve farther down upon its sides than in the recent genus. Everywhere they are convex transversely and, for much of their length, they are con- vex longitudinally also, but anteriorly, owing to the slight upturning of the end of the rostrum, they become somewhat concave in this direction. Dorsally, the nasals project well beyond the premaxillaries, though not so far as in Tatu, and their free ends are abruptly truncated and rounded, not bluntly pointed as they are in the latter. The anterior nares are very oblique and have nearly the same shape as in the recent genus, but are rather lower and wider. The premaxillaries are likewise much longer than in Tatu, but do not rise so high upon the sides of the rostrum, of which they form less and the nasals more than in the recent genus. Posteriorly, the premaxillaries are very low and are extensively overlapped by the maxillaries. On the ventral side, the anterior ends of the premaxillaries are curiously similar to what is to be seen in the modern genus : there is a short median pro- cess and each bone has two lateral notches, the outer one above and a little in advance of the inner. The palatine processes are narrow, somewhat con- vex and of almost uniform width throughout, though broadening slightly toward the hinder end ; they curve uninterruptedly into the sides of the tubular rostrum. The incisive foramina are elongate and very narrow slits, separated by a slender spine and continued posteriorly by long, shallow grooves. The maxillaries, like all the bones that enter into the formation of the rostrum, are more elongate than in Tatu, while the facial portion is much less inflated, so that externally it projects much less beyond the plane of the teeth and the forward contraction of the rostrum is more gradual. However, this facial region is decidedly inflated and indicates the presence of large antra. The zygomatic process is much shorter than in the exist- ing genus and less expanded vertically, nor does it extend beneath the jugal, with which it has a very short and almost vertical suture. The in- 20 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. fraorbital canal is very short and has a much more anterior position than in the recent genus ; posteriorly it is continued as an open groove, which is not indicated in the latter. In correlation with the extreme reduction of the teeth, the alveolar process is quite insignificant, but its edentulous portion is extended forward for the whole length of the maxillary, as a delicate though distinct ridge, which sharply demarcates the palatal from the facial surface. The very long palatine processes are widest between the teeth, narrowing somewhat behind them and still more, though very gradually, in front of them. As a whole, the maxillary portion of the palate is slightly concave transversely, but each palatine process is convex in the same direction, which is produced by a deep median groove, with a low ridge along the line of suture. Groove and ridge are much more distinct in one of the specimens than in the other and are not apparent in Tatu. The palatines are quite large and form a considerable extent of the hard palate ; their external borders, as in the maxillary region, are thin ridges, which distinguish the lateral from the palatal surface ; these ridges con- verge posteriorly, where the infero-lateral surface of the palatines becomes quite broad, and are continued over upon the pterygoids. Unfortunately, the shape of the posterior nares cannot be clearly made out in either speci- men, as the edges are broken ; it is apparent, however, that the opening is much longer and narrower and extends farther forward between the pala- tines than in Tatu. The pterygoids are small bones, mostly concealed from view by the pos- terior extension of the palatines. Hamular processes and fossae are absent, but the free border is broadened and thickened, though without the swollen appearance seen in Tatu; this border forms an angulation between the ventral and posterior sides, such as does not occur in the modern genus. The vomer, which is very long and narrow, is not visible in the pos- terior nares, but extends along the ventral side of the mesethmoid. The latter is very extensively ossified, forming a complete nasal septum, with thickened dorsal and ventral borders. Beneath the cribriform plate it curves downward behind the vomer and unites with the palatines. The cranial foramina are quite characteristic. High up in the orbit is a long vertical slit, which encloses two separate foramina ; of these, the upper one is the optic foramen and the lower one is the foramen lacerum ante- rius. In the same vertical line with the latter, but well below it, is the EDENTATA OF THE SANTA CRUZ BEDS. 21 foramen rotundum and behind this, on the same horizontal line, is the foramen ovale. A large, irregular opening in front of the tympanic ring probably includes both the eustachian canal and the foramen lacerum medium, while the posterior lacerated foramen is a narrow, slit-like open- ing behind the petrous portion of the periotic. The glenoid foramen, which is present in Tatu, appears to be wanting, but the stylo-mastoid foramen is large and distinct. The condylar foramen has nearly the same position as in the existing genus, but is larger and more conspicuous. The mandible is extremely peculiar and although it may be not inade- quately described as that of Tatu in a very exaggerated form, it suggests, at first sight, a likeness to the jaw of an anteater. The horizontal ramus is very long, slender and laterally compressed ; its posterior portion has a slightly thickened alveolar border to carry the minute teeth, but, for much the greater portion of its length, it is a narrow, edentulous ridge ; the anterior portion tapers forward more gradually than in Tatu and ends in a blunter point and the inner surface of the jaw is quite concave. The symphysis is merely a very short contact between the rami at the fore- most end of the jaw. The ascending ramus is very low, but very broad antero-posteriorly, and the condyle is placed far behind the teeth, though relatively not so far as in Tatu, and is much lower in position than that of the latter; the masseteric fossa is obscurely marked, but large and becoming quite deep beneath the condyle. The anterior border of the ascending ramus is a long, gentle and slightly concave slope, though the coronoid proper is a very low, relatively broad, and recurved hook, entirely different from the high, slender and pointed coronoid of the existing genus. The sigmoid notch is very wide and shallow, in marked contrast to the much narrower and deeper notch of Tatu. The condyle is especially peculiar; it is sessile, longitudinal and scroll-shaped, being strongly curved toward the inner side of the jaw, and convex in both directions ; it is altogether different from the condyle of the modern genus. The notch between the condyle and angle is much broader and deeper than in the latter, in which the angle is greatly reduced, while in the fossil it is a broad, very thin plate and forms a blunt hook, which projects well behind . the condyle. There are two mental foramina, one which opens below the anterior teeth and is large and conspicuous, the other, much smaller, is considerably in advance of this. The inferior dental foramen, which is also large, is placed high up on the inner side of the 22 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. ascending ramus, with a broad and deep groove leading back from it toward the condyle, which groove is not shown in Tatu. Vertebral Column ; Ribs and Sternum. — The cervical vertebrae are of distinctively armadillo-like character and, in particular, resemble those of Tatu. In proportion to the size of the head the neck is short, though decidedly longer than in Dasypus, stout and heavy. The atlas is shaped much like that of Tatu, being short, broad and high and considerably surpassing that of the latter genus in the dorso-ventral diameter. The anterior cotyles are quite narrow and nearly plane transversely, high and concave dorso-ventrally ; each is notched near the ventral side and the articular surface is invaded by a sulcus corresponding to that on the occi- pital condyle. The posterior cotyles are broad, low and quite concave and present obliquely inward. The sides of the atlas are high, flattened, and nearly vertical on their outer faces, meeting the neural and inferior arches almost at right angles, which gives to the bone a characteristically quad- rate shape. The neural arch is narrow antero-posteriorly, the cotyles projecting freely in front of and behind it, and is moderately convex on the dorsal side, while the neural spine is a low, but heavy, rugose and quite conspicuous tubercle. The inferior arch is slender and less strongly curved than the neural. The neural canal is somewhat different in shape from that of Tatu, being considerably higher than it is wide and divided into nearly equal dorsal and ventral portions by the tubercles for the attachment of the transverse ligament, while in the modern genus the lower portion is the larger of the two. As in the existing genus, the transverse process is greatly reduced, though it is more prominent than in the latter, forming merely a roughened and thickened, imperforate eleva- tion on the posterior part of the dorso-lateral angle. The hinder opening of the vertebrarterial canal is above the inner part of the posterior cotyle and is so covered by the extension of the neural arch as to be concealed, except when the atlas is viewed from behind ; the canal passes forward and downward, opening in a conspicuous foramen on the outer side of the bone. The only other foramina are those perforating the neural arch for the passage of the first pair of spinal nerves. The axis and the two succeeding vertebrae (Plate IV, fig. i) are com- pletely fused into one long compound bone, though the elements of this may still be distinguished by the sutural lines. In length, the axis makes up nearly one half of the compound mass, exclusive of the odontoid pro- EDENTATA OF THE SANTA CRUZ BEDS. 23 cess ; the narrowest portion is just behind the cotyles of the axis and thence the mass widens posteriorly, though the widening is due princi- pally to the coalesced transverse processes, the centra remaining of nearly uniform breadth and very much depressed ; the mass has a faintly marked median, ventral keel, which is best developed on the axis, and on each side of this keel a number of obscure, oblique lines, converging forward ; the centrum of the fourth cervical is made opisthoccelous by the projection of its dorsal and ventral edges, though transversely it is plane. The odontoid process of the axis is slender and of depressed cylindrical, rather than conical form, and on its ventral side is a well-defined, saddle-shaped facet for the inferior arch of the atlas. The cotyles for the latter are low, broad and convex in both directions. In one of the specimens, but not in the other, the dorsal border is notched for the vertebrarterial canal, which opens just behind it and has a slightly more elevated position. The neural canal is quite high and of trihedral shape at the front end of the axis, becoming very low and broad on the fourth cervical, so that the combined neural arches slope downward and backward. The neural spine of the axis and the third cervical are fused together into one large, hatchet- shaped plate, much the greater part of which is contributed by the axis. In shape this compound spine seems to differ somewhat in the two speci- mens, though in neither is it sufficiently complete to admit of exact com- parison. On the fourth cervical the spine is very low, almost obsolete, and is not united with that of the third vertebra. The coalesced zyga- pophyses make a continuous ridge on each side of the neural arch, en- larged at the points of union between the vertebrae and becoming espe- cially conspicuous on the fourth. The transverse processes also form continuous ridges, ending behind in large, simple, diverging and rod-like projections, but for most of their length they are depressed, shelf-like plates, with thin edges. Thus, the vertebrarterial canal is a long tube, the large and conspicuous anterior opening of which is just behind the cotyle of the axis, while the posterior opening is concealed in the trans- verse process of the fourth cervical. On the ventral side of the trans- verse process each vertebra of the compound mass has a foramen opening into the vertebrarterial canal ; these foramina seem to be peculiar to the present genus. The spinal nerves make their exits through foramina, which in the axis perforate the pedicles of the neural arch, but elsewhere have an intervertebral position. The fifth cervical is shorter and broader 24 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. than the fourth and has a much depressed and transversely arched cen- trum, with concave posterior face which is extended out upon the trans- verse processes ; the pedicles of the neural arch are low and narrow, bringing the zygapophyses of each side very close together ; the neural arch is extremely slender, leaving a wide space between itself and the arch of the succeeding vertebra ; the transverse process is quite distinctly divided into dorsal and ventral portions and each of these is again divided into anterior and posterior processes, both of which function as additional zygapophyses, articulating with the corresponding processes of the fourth and sixth vertebrae. In neither specimen is the sixth or seventh cervical preserved. Of the thoracic vertebrae the first and second and the last five are pre- served in connection with one specimen, and the third and fourth with the other, but the nine vertebrae do not form a continuous series and the region must have had at least eleven. In general the thoracic vertebrae resemble those of Tatti but they are relatively heavier and there are some differences of detail. The first thoracic has a broad and depressed centrum, like that of the cervicals in shape, but much more elongate and narrower posteriorly ; the neural canal is quite large and the spine very long, broad, laterally com- pressed and much heavier than that of Tatu. At the upper end this spine is coossified with that of the second vertebra, but this is doubtless merely an individual peculiarity. The spine is strongly inclined backward with reference to the long axis of the centrum, but owing to the curvature of the vertebral column in this region it has a nearly erect position. The prezygapophyses, which are of the cervical type, are large, widely separated and placed on the pedicles of the neural arch but little above the level of the centrum, while the postzygapophyses are of the thoracic type and situated on the ventral side of the neural arch. Although they are both broken away, it is evident that the transverse processes were very large and, as in Tatu, extended forward, enclosing and almost concealing the last cervical. The second thoracic is similar to the first, but has a somewhat thicker centrum of more uniform breadth, a much smaller, transversely oval neural canal, prezygapophyses placed on the neural arch, and a higher, somewhat more slender and less steeply inclined spine ; the transverse processes are broken on this vertebra also, but enough remains to show that they were less massive than on the first. EDENTATA OF THE SANTA CRUZ BEDS. 25 The third and fourth thoracics have smaller, but still broad, depressed and opisthocoelous centra, and very small and low neural canal ; the neural spines are slender and have a more decided backward inclination than those of the first and second vertebrae ; the transverse processes are long, subcylindrical and upturned at the end, where they bear facets for the tubercles of the ribs and indicate that in this region the ribs had long necks. As in Tatu, each transverse process is pierced by a foramen which enters the process on the posterior and opens on the ventral side. Minute, incipient metapophyses are present on the fourth vertebra, arising from the front side of the transverse processes, near the base. The last five thoracic vertebras gradually take on the characters of the lumbars. The centra, which are remarkably depressed throughout, grow larger posteriorly ; the neural spines become shorter, heavier, less strongly inclined backward, more expanded and thickened at the free end ; the meta- pophyses increase rapidly in size, until, on the last vertebra, they are as long as the spine, inclining steeply forward and outward ; the transverse processes diminish as the metapophyses increase and are very short on all of these vertebrae. On the tenth and eleventh vertebrae (assuming that eleven is the number of the thoracics) the facet for the tubercle of the rib is brought into immediate juxtaposition to that for the head, which, on the tenth and especially on the eleventh, is very large, prominently projecting and deeply concave ; the perforation of the transverse processes continues as far back as the eighth vertebra. The accessory articular processes are already present on the seventh vertebra and they may well have been present on the sixth, as they are in Tatu. On the seventh thoracic the postzygapophyses, though still very small, are of the lumbar type and an articular surface is developed on the anapophysis, which is overlapped by a corresponding facet on the metapophysis of the eighth vertebra, and thus there are two pairs of postzygapophyses on the seventh and of prezygapoph- yses on the eighth. Between the ninth and tenth vetebrae an additional pair of articulations is developed, a posterior one on the ventral side of the anapophysis of the eighth and an anterior one on the dorsal side of the transverse process of the ninth. On the last two thoracics these articular surfaces become larger and more conspicuous. The last four thoracic vertebrae have deep grooves on the sides of the centra, extending downward and forward from the intervertebral foramina and continued anteriorly upon the ventral side ; they become deeper on 26 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. each succeeding vertebra and are most conspicuous on the last one. Curi- ously enough, these grooves are asymmetrical, being longer and deeper on the right side than on the left. The lumbars are four in number and this, with eleven thoracics, would give a total of fifteen trunk-vertebrae, the formula common in Tafit, though in that genus the number varies from thirteen to sixteen. The lumbar centra are of moderate size, not greatly exceeding those of the posterior thoracic region, nor do they increase much in size backward, though that of the third is somewhat larger that the others ; they are short, broad and depressed and the second has on the ventral side a pair of short, parallel ridges, which are repeated, though very obscurely, on the third and fourth ; all the centra, except the fourth, have grooves like those of the last four thoracics, which are best shown on the first. The neural spines are some- what longer and broader than those of the hindermost thoracic region and are recurved rather than inclined ; the free end of each spine is thickened and cleft behind to receive the anterior edge of the succeeding spine ; the metapophyses are exceedingly prominent and reach their maximum size on the third vertebra. Each of the lumbars has three pairs of articular processes in front and behind. The sacrum is much like that of Tatu, being very long and composed of nine vertebrae intimately fused together. As a whole and seen from the dorsal side, the sacrum is broad in front, narrows gradually to the end of its contact with the ilium and then again expands, but more suddenly, and attains its greatest breadth at the hinder end. Ventrally, the sacrum is very narrow in front, broadening posteriorly. These alternate con- tractions and expansions affect chiefly the transverse processes, the centra narrowing regularly from the first to the last, though in the middle region they become extremely thin and plate-like. The neural spines form a low continuous ridge and the neural canal is small. The first sacral vertebra has very prominent metapophyses and two pairs of prezygapophyses, like those of the lumbars, but on the other vertebras, except the eighth and ninth, the zygapophyses have entirely disappeared. Vertebrae one to three are connected with the ilia, ventrally by pleurapophyses and dorsally by the transverse processes, while the fourth reaches the ilia only by means of the latter. Next follow two vertebrae which are not in contact with the pelvis at all, succeeded by three which unite with the ischia by their greatly developed transverse processes. EDENTATA OF THE SANTA CRUZ BEDS. 27 Fifteen caudal vertebrae (Plate IV, fig. 2) in apparently uninterrupted succession, are associated with one of the specimens ; the series, however, is not complete, for another vertebra which is preserved, is evidently sepa- rated from the fifteenth by a gap, and several of the terminal joints are missing. These vertebras indicate a longer tail than has been observed in any other Santa Cruz armadillo and one which probably was not as long in proportion as that of Tatu, but was broader and more depressed. The first caudal has a short, broad, somewhat depressed centrum, with trans- versely oval and slightly concave faces ; on the ventral side are grooves, which start from the hinder border of the transverse processes, converge forward, enclosing between them a raised, triangular area. The neural canal is low, but quite wide, and the neural spine very low, while the zygapophyses are complete, though simple. The transverse processes are remarkably long and straight, extending directly outward from the centrum and slightly widened and thickened at the distal end. These processes, which are much the most striking feature of the vertebra, are very similar to those of the last sacral, and their breadth is nearly equal to the length of the centrum. Passing backward toward the end of the tail, the centra gradually become reduced in diameter, but increase in length ; none, however, is more than moderately elongate and they are relatively much shorter than the corresponding bones of Tatu. The maximum length is reached in the sixth caudal and is maintained with hardly any change to the fifteenth, and even the much more slender isolated vertebra, which may be taken as the seventeenth, is almost as long as the fifteenth. All the centra have the ventral grooves above described, but they gradually be- come very obscure ; on vertebras one to four these grooves are continued around the sides of the centra to the hinder opening of the neural canal. Small haemapophyses for the attachment of chevron-bones are present on all the caudals, except the first, and perhaps on that one also, but, if so, they are very feebly developed. Zygapophyses cease quite abruptly on the eighth vertebra, which has long anterior, but no posterior pro- cesses. Metapophyses, on the other hand, persist on all of the caudals, diminishing posteriorly. The neural canal diminishes rapidly, but re- mains, as a fine, hair-like tube, as far back as the fifteenth vertebra, on which it is, for most of its length, a very narrow groove ; no trace of the canal appears on the ? seventeenth. The neural arch is high, especially behind, where it carries the postzygapophyses, and even after the latter 28 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. have disappeared, the arch continues as a prominent ridge, with a wedge- shaped top, and is recognizable even on the ? seventeenth caudal. Distinct neural spines occur only on the first and second vertebrae. The transverse processes diminish gradually in length throughout the series, but are distinct even on the ? seventeenth. Vertebrae one to four have similar transverse processes, except that on the fourth the ends are vertically expanded and decurved in a way that does not occur in any other vertebra. At the fifth caudal a comparatively sudden change occurs, the transverse processes becoming broader and curving forward, and at the distal end the breadth of the process exceeds the length of the centrum, an arrangement which continues to the twelfth. These broad, wing-like processes are very char- acteristic of the present genus and are quite different from those in the corresponding region of Tatu, in which the breadth of the processes is much less than the length of the centrum, and consequently the intervals between the successive processes are much greater than in the fossil. Seven chevron-bones are associated with the same individual, none of them, unfortunately, in position ; they are triangular in shape and perfor- ated by a canal for the caudal artery and vein. Anteriorly, the chevron- bones are narrow in the fore-and-aft dimension and, when viewed from the end, have the shape of a nearly equilateral triangle, with a large perfora- tion ; posteriorly, they become shorter dorso-ventrally, broader and more canoe-shaped, while the canal is reduced. Of ribs, two are preserved. The first rib is of the usual armadillo pat- tern ; it is short, but extremely broad and plate-like, with concave inner, straight outer and convex ventral border. The other ribs are relatively broad and in shape resemble those of Dasypus, rather than those of Tatit. Of the sternum, the posterior segment, or xiphisternum, has been re- covered ; it is quite broad in front, tapering posteriorly, and its anterior end has two facets for the sternal ribs, separated by a distinct notch. Appcndicular Skeleton. — The scapula (Plate IV, fig. 3), is quite peculiar and differs from that of any other Santa Cruz genus, as well as from that of any existing armadillo with which I have been able to compare it, being remarkably small, both in height and in the breadth of the dorsal part. On the whole, the nearest resemblance is with the shoulder-blade of Tatn, though there are many differences. The neck is broad, more so than in Tatn, and there is no coraco-scapular notch, a marked distinction from Dasypus ; the coracoid border is concave for about half its length and then EDENTATA OF THE SANTA CRUZ BEDS. 29 becomes convex, curving gradually into the suprascapular border, while in both of the last-named genera the two borders meet at an angle. So far as it is preserved, the suprascapular border is regularly arched, but, as the postero-superior angle of the blade is broken away, I cannot determine whether or not it had the remarkable prolongation seen in most recent armadillos. It may be inferred, however, that the angle was much less produced in the fossil, because the glenoid border is nearly straight, not concave ; this border is thickened and forms a ridge, which is roughly parallel with the spine and, while rather more conspicuous than in Tatu, is much less so than in most other modern genera. The spine is placed slightly behind the middle of the blade, making the prescapular fossa a little larger than the postscapular ; it is high and very strongly recurved, so as to have a deeply concave posterior side. The acromion is broad, thin and curved forward ; so far as it is preserved, it resembles that of Tatu, except in having a smaller metacromion, but it is so broken that its length is in- determinable. The glenoid cavity is shallow, narrow transversely, but quite elongate, and the coracoid is small. The humerus (Plate IV, fig. 4) exhibits some peculiarities ; the head is elongate, narrow and quite strongly convex in both directions, projecting somewhat behind the plane of the shaft ; the external tuberosity, though broken, was evidently very large, while the internal one is greatly reduced, as in Tatu, bringing the bicipital groove, which is narrower than in the latter genus, to the inner angle of the proximal end. The deltoid area, though larger and more prominent than in Tatu or Dasypus, is not so well developed as in the other Santa Cruz genera ; it is broad and rugose with prominent borders, which give a concave shape to the sides of the shaft. The latter is short and heavy and of the usual shape, compressed and thick proximally, broad and thin distally ; the supinator ridge is very prominent, adding much to the breadth of the distal part and its outer border passes upward into a raised line, which extends on the hinder face of the shaft to the inner tuberosity ; the internal epicondyle is very large and massive and the foramen is also large. The trochlea is quite different from that of Tatu or Dasypus, being broad and low, but increasing in vertical diameter towards the inner side and ending on that side in an unusually prominent sharp-edged flange, which is highly characteristic ; the tuberosity for the head of the radius is much more convex and distinct than in the other Santa Cruz genera and shifted nearer to the median line. 30 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. The anconeal fossa is deeper than in the other contemporary armadillos, while the supratrochlear fossa is of only moderate depth. No portion of the forearm or manus has been found, which is especially unfortunate, as the humeral trochlea indicates a somewhat peculiar char- acter of the ulna and radius. The pelvis is very much like that of Tatu. The ilium is long, slender, and trihedral, with strongly everted anterior end ; the acetabular border is a thin ridge, external in position, which makes the gluteal surface pre- sent dorsally and the iliac surface ventrally. As in the modern genus, the anterior end of the ilium is not expanded into a plate, but is much thick- ened and club-like, with very rugose crista ; the suprailiac border is very FIG. 6. Pelvis of Stegotheriuin tesselatnm, left side ; x f . long and is extended farther back along the sacrum than in Tatu, mak- ing the ischial border much more concave, and the peduncle of the ilium is relatively shorter and heavier and the sacro-sciatic foramen is conse- quently smaller. The pubic border is broad, rounded and ill-defined ; near the acetabulum it supports an ilio-pectineal process, which is remark- ably large and rugose, though not very prominent. In no other known Santa Cruz armadillo is such a large process to be found. The acetabulum is large and presents downward almost as much as outward ; the dorsal border is given a notched appearance by the prominence of the anterior end and the articular surface is deeply invaded by the sulcus for the round ligament. The ischium is short, but broad and plate-like, and has a heavier appearance than in Tatn, the descending branch being much broader than in the latter. In the specimen before us the ischium is com- EDENTATA OF THE SANTA CRUZ BEDS. 31 pletely fused with the transverse processes of the last four sacral vertebrae, but with the posterior angle rising well above the sacrum and thickened to support the carapace. As the limits between the pubis and ischium cannot be distinguished, it is uncertain whether the latter enters into the symphysis or not. The pubis is quite slender, though decidedly stouter than in Tatu and forms a longer symphysis than in the latter ; the obtu- a FIG. 7. Pelvis of Stegotherium tesselatum, x §. «, dorsal view ; b, ventral view. rator foramen is relatively smaller than in the recent genus and of a more regularly oval shape. The femur (Plate IV, fig. 5) resembles that of Tatu; the hemispherical head is set upon a broad and thick, but distinct neck and presents upward more than inward ; the notch between head and great trochanter is much deeper than in Dasypus, broader and more V-shaped than in Tatu; the pit for the round ligament is a large, shallow, triangular depression on the posterior aspect of the head, emarginating the articular surface and not 32 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. enclosed by it. The great trochanter is high and thick, rising well above the level of the head, though hardly so large proportionately as in Tatu; the digital fossa, though better defined than in the latter, or in Dasypiis, is extremely small and shallow. The second trochanter is a long, prom- inent, rugose ridge, which is more widely separated from the head and is longer proximo-distally, but much less prominent than in Dasypiis. The third trochanter has about the same relative position as in Tatu, but is not so prominent, nor so much curved forward. The shaft is very broad and much more compressed antero-posteriorly than in either of the last named modern genera; it has a very decided outward curvature, which would be regular, were it not for the second and third trochanters ; aside from the former, the inner border is quite regularly concave, while below the third trochanter on the outer border is a sharp ridge, which ends in the tuberosity. The anterior face of the shaft is much less convex than in Tatu and the posterior face is nearly flat. The rotular groove is broad and shallow, decidedly more so than in Dasyptis or Tatu, being almost plane transversely ; there is no suprapatellar fossa. The condyles, which are widely separated, are small and of unequal size, the internal one con- siderably larger than the external. As in the armadillos generally, the tibia and fibula (Plate IV, fig. 6) are coossified at both ends. The tibia is of nearly the same length as the femur exclusive of the great trochanter ; the proximal facets are of nearly equal size, but of different shape ; the external facet is convex and the in- ternal is at a lower level and concave ; there is no tibial spine other than a slight elevation of the mesial border of the inner condyle. The cnemial process is long and prominent and is continued into a ridge which reaches to the distal end, as in Tatu. The shaft is strongly arched toward the inner side and is moderately curved forward ; its external border is a ridge distinct from that which fuses with the fibula. On the postero-internal angle of the distal end is a deep tendinal sulcus between the internal malleolus and the posterior tongue-like process. The astragalar surface is broad, but much compressed antero-posteriorly, and is divided into two facets, of which the external one is deeper and more concave ; the inter- condylar ridge ends posteriorly in a tongue-like process, which is much more prominent than in Tatu. The fibula is laterally compressed and plate-like ; the distal end, which forms a heavy external malleolus, bears a small but distinct facet for the calcaneum ; the sulcus for the peroneal tendon is very obscure. EDENTATA OF THE SANTA CRUZ BEDS. 33 The hind-foot (Plate IV, fig. 7), which belongs to No. 15,565, differs in many respects from any other pes that has been found in the Santa Cruz beds. The astragalus has the short, broad, depressed form usual in the arma- dillos, but the trochlea is more deeply grooved than in the other Santa Cruz genera and is divided into two very unequal condyles, of which the ex- ternal one is much the broader, while the internal is higher and more con- vex ; the fibular facet is somewhat everted at the plantar edge, and the external calcaneal facet is very large and concave and much produced ex- ternally, while the sustentacular facet is small, of elongate, subquadrate shape and entirely isolated from the other. The neck is short, broad and depressed and has a shallow depression on the dorsal side ; the head is transversely convex, very low in the dorso-plantar dimension. The calcaneum is conspicuously different from that of any other known Santa Cruz armadillo ; among existing genera, it most resembles that of Tatu. The tuber is very elongate, longer than in the latter, and com- pressed, but deep in the dorso-plantar diameter, with no expansion at the free end ; the dorsal border is nearly straight, the ventral somewhat sinu- ous ; at the proximal end is a very short, but distinct, tendinal sulcus. The external astragalar facet is short, but very broad transversely, projecting out beyond the side of the tuber, and its outer end bears a small facet for the fibula, which is continuous with the fibular facet on the astragalus, when the two bones are in position. The sustentaculum is very promi- nent, but narrow and pointed and bears a small, isolated, subcircular facet for the astragalus. The cuboid facet is small and but slightly concave, narrowing to ward the plantar side; external to it is a large, rugose tubercle. The navicular is broad, short and thin and is not extended up on the inner side of the astragalar head, as it is in most armadillos. On the plantar side is a prominent, hook-like process and on the distal end are three well- distinguished facets for the cuneiforms ; the cuboid surface is a narrow band on the plantar side. The entocuneiform is shaped much as in Dasypus, being relatively large, but thin and scale-like ; its facet for the navicular is concave, oblique and somewhat warped ; that for metatarsal I is saddle-shaped. The mesocuneiform is small, but not so much reduced as in Dasypus or Tafti, and its principal diameter is the dorso-plantar; the exposed dorsal surface is nearly square and both proximal and distal ends are concave. 34 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. The ectocuneiform is relatively larger than in Dasypus, though hardly so broad as in Tatu; on the dorsal surface the transverse diameter exceeds the proximo-distal, but the bone contracts much toward the plantar side ; distally, it expands beyond the head of metatarsal III and has a consider- able contact with metatarsal IV. The cuboid is quite small, but little exceeding the ectocuneiform in size and of irregularly pyramidal shape. On the outer side is the cal- caneal facet, which is external rather than proximal, almost plane and very oblique, sloping upward and inward and nearly meeting the large navicular facet ; the distal end is principally occupied by the large facet for metatarsal IV, that for metatarsal V being very small. As in the armadillos generally, the metatarsus consists of five members, the median three much larger than the laterals (I and V) which are greatly reduced in length, though not in breadth or thickness. In shape and pro- portions these bones most nearly resemble those of Tatu, though they are more massive. Metatarsal I is extremely short and heavy, no longer than a phalanx, to which it bears considerable resemblance ; the proximal end has a very large, saddle-shaped surface for the entocuneiform and the distal end an extremely low trochlea, with very short, though prominent, plantar keel. Metatarsal II is more than twice as long as metatarsal I and very heavy ; the proximal end is narrow, bears a very oblique and nearly plane surface for the mesocuneiform and rises well above the level of metatarsal III, so as to have an extensive lateral contact with the ectocuneiform ; the shaft is broad and depressed, of somewhat irregular shape, widening to the distal end, which has a very low trochlea, with a median depression on the dorsal side and a prominent keel on the plantar. Metatarsal III is the longest of the series and is narrower and thicker than metatarsal II ; the proximal end is slightly broader and considerably thicker than the shaft, which is of nearly uniform width, though broaden- ing somewhat at the distal end, and is of trihedral shape, not compressed planto-dorsally ; the trochlea is well developed, higher and reflected farther upon the dorsal side than in any other member of the series. Metatarsal IV is longer than metatarsal II, but considerably shorter than metatarsal III ; it has a broad, very oblique proximal end, which articulates with both ectocuneiform and cuboid, as in / FIG. 25. Bones of the hind limb of Santa Cruz Gravigrada, x \. a, Hapalops (femur of H. elongatus, tibia and fibula of H. longiceps) ; b, Analcimorphus leptoceplialus ; c, Prepotherium potens. in at least two genera, Schismotherium and Analcimorphus, the shaft is much more rounded and less compressed ; the third trochanter is present in every known specimen, but is much reduced in Prepotherium; the great trochanter is low, but very massive and the digital fossa is ex- tremely small ; the condyles usually resemble those of Megalonyx and the rotular trochlea is broad and shallow. PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. (17) The patella is almond-shaped and of no great thickness. ' (18) The tibia and fibula are never coossified. The tibia is short and heavy, but much less so than in the Pleistocene genera; the proximal end is antero-posteriorly compressed and has widely separated facets for the femoral condyles; the shaft is arched forward and the cnemial process, though heavy and rugose, is inconspicuous; the distal end is broad and much compressed antero-posteriorly; the inner malleolus is Pes of Santa Cruz Gravigrada, x c, Pelecyodon arcuatus. IV FIG. 26. a, Hapalops longiceps ; b, Analcimorphus leptocephalus ; very small, but internally to it there arises a prominent process, which is grooved by a tendinal sulcus ; the astragalar surface varies consider- ably in the different families and genera. (19) The fibula is stout and straight, with subcylindrical shaft and extremely massive distal end, which has no contact with the calcaneum. (20) The pes, though known in only a few genera, displays consider- able variety of structure. In the Megalony chides the astragalus is essen- tially similar to that of the Pleistocene members of the family ; it is rela- tively narrow and elongate, with trochlea which may be but slightly or quite distinctly grooved ; the neck is very short and the navicular facet is concave. In the Planopsidcg, as represented by Prepotherium, the astrag- alus is of quite a different type, being shorter and much broader and with quite deeply grooved trochlea ; the inner condyle is short and strongly convex and projects prominently toward the internal side, thus displaying in an incipient stage the odontoid form of this condyle seen in Mega- therium and Mylodon. EDENTATA OF THE SANTA CRUZ BEDS. 175 In the Megalonychidce the calcaneum resembles that of Megalonyx and Notkrotherium, especially in the broad, depressed, curved and plate-like tuber; the sustentaculum is not very prominent and its facet for the astragalus presents almost distally, so as to be nearly parallel with the surface for the cuboid ; the latter surface is quite concave and of subcir- cular shape, covering the entire dorso-plantar diameter of the distal end. In Prepotherium the calcaneum displays some significant differences ; the tuber is not notably different, being a similar broad, depressed and curved plate, but the sustentaculum is very much more prominent and its facet for the astragalus presents dorsally, at right angles to the plane of the cuboid facet ; the latter is remarkably narrow in the dorso-plantar dimension and below it is a thickened mass of bone. Doubtless, these differences indi- cate that Prepotheritim had already begun to rest the weight in walking upon the fibular border of the hind-foot. FIG. 27. Dorsal side of right astragalus, nat. size, a, Hapcdops elongatus ; b, Prepotherium potens. The remainder of the pes is known in only a few genera of the Mega- lonychidce, such as Hapalops, Analcimorphus and Pelecyodon, and shows an unexpected amount of difference between them, which, however, is chiefly confined to the relative proportions of the digits. The tarsal bones are all present and unankylosed and the digits number five, all functional and bearing claws. In Hapalops the three radial metatarsals (I-IH) are very short, and II and III are extremely heavy, while IV and V are much more slender and elongate ; V gives off from the proximal end of the fibular border a very large and prominent process, as in Megalonyx, in which PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. the metatarsals are far heavier, but retain their relative proportions. In Analcimorphus and Pelecyodon, on the other hand, the difference in length is very much less marked ; II and III are, it is true, much stouter than IV and V, but they are not strikingly shorter, and V has no such development of the proximal process as in Hapalops. «, b FIG. 28. Distal end of right calcaneum, nat. size, a, Hapalops elongatus ; b, Prepotherium potens. as, external astragalar facet ; as internal astragalar, or sustentacular facet ; cb, cuboid facet. The phalanges, which are all free, resemble those of the manus, but the unguals are considerably smaller. The systematic arrangement of the Santa Cruz Gravigrada offers an exceedingly puzzling and difficult problem. At that period the entire group would appear to have been in a state of flux, as though the types had not yet been definitely fixed, and I know of no series of fossil mam- mals which so strongly suggests indefinite variations, from which a com- paratively small number were chosen and fixed by natural selection. Not only is there a great number of types, but these types are also, within comparatively narrow limits, singularly variable and inconstant, so that it is exceptional to find two individuals which are clearly and unequivocally referable to the same species, and every imaginable transition may be found. To depend upon the usual criteria, would result in the formation of a different species for almost every specimen and the number of species, already very large, would be greatly increased by the Princeton and New York collections, in which few individuals agree at all closely with those in the collections of Dr. Ameghino and the La Plata Museum. Differ- ences of age may perhaps account for some of these variations and others may possibly be due to sex, for there are, in a few instances, indications EDENTATA OF THE SANTA CRUZ BEDS. 177 of secondary sexual characters, but the analogy of the recent edentates does not encourage us to expect any very notable sexual differences in the fossil skeletons. Even less than usual is it possible to be consistent in the employment of specific and generic criteria ; a character which in one group is altogether variable and of no taxonomic value, may in another be quite constant and prove of much assistance in distinguishing the species. While the genera may, as a rule, be separated without great difficulty, the only practicable course, in the present state of knowledge, is to regard the species as vague and elastic groups, partly on account of their variability and partly because so many have been established upon fragmentary remains. The satisfactory taxonomic arrangement of the Santa Cruz Gravigrada must await the gathering of much more extensive collections. I have attempted in the following pages to furnish the reader with material adequate to an independent judgment of these questions. Attention has already been called to the fact that the Gravigrada of the Santa Cruz beds have great phylogenetic importance and that represen- tatives, if not actual ancestors, of almost all the Pleistocene genera may be found in this fauna. It should be observed, however, that the number of Santa Cruz genera much exceeds that of the Pampean types, most of the former having died out without successors. As examples of this may be cited Ettckolceops, Analcimorphus, Pelecyodon, and many others. On the other hand, several of the genera may well have been the direct ances- tors of later forms. The Pleistocene Nothrotherntm might be sufficiently described as Hapalops with the dental formula reduced to £ and with the pterygoids curiously inflated. It is extremely probable that the North American Megalonyx is descended from some of the Santa Cruz Megalony- chidce, for there is the closest correspondence between them in all parts of the skeleton ; the Pleistocene genus is very much larger and more mas- sive and the skull has undergone considerable modification, but otherwise there is singularly little change. Among the Santa Cruz representatives of the family, the one most likely to prove the desired ancestor is Mega- lonychotheriitm, which already displays the characteristic type of dentition, but this genus is still too incompletely known for certainty in the matter. It is extremely unfortunate that the Planopsidce and Mylodontidce are so rare and are represented in the collections by such incomplete speci- mens. Under these circumstances it is impossible to decide questions of phylogeny with any degree of confidence. So far, however, as the evi- iy8 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. dence extends, there is much reason to believe that Prepotherium is nearly allied to the ancestor of Megatherium, and that Nematherium and Analci- therium were the fore-runners of Mylodon, Lestodon and Scelidotherium. Finally, should be remarked another notable difference between the Santa Cruz Gravigrada and those of the Pampean. In the former epoch the Megalonychidce were the dominating family, which included the greater number of genera and species and the overwhelming majority of individ- uals, while the other two families are so rarely found that they must have formed but an inconspicuous element of the fauna. In Pampean times, on the contrary, most of the Megalonychidce had become extinct and the Megatheriidce and Mylodontidce had greatly increased and assumed the dominating position. MEGALONYCHIDCE. In the Santa Cruz epoch, at least in Patagonia, this was the characteristic family of Gravigfada, far outnumbering in genera, species and individuals both of the other families combined, and it is the only one of the three in which the skeletal structure is at all completely understood, but enough is known of the other two families to display many of their contrasting characters. The present family includes many very small species, the smallest of the known Santa Cruz ground-sloths, as well as some of the largest, with every intermediate gradation of size. The teeth are non- lobate and may be arranged in continuous series, or, as is much more common, with the first tooth in each jaw isolated by diastemata and, though varying much in size and shape, always more or less distinctly caniniform ; - is usually implanted in the jaw near the maxillo-premax- illary suture, but in a few genera is placed considerably behind that suture. The molariform teeth are most frequently of transversely oval form, but are often rectangular or subtrihedral. The skull is elongate and cylindrical, usually with deep postorbital constriction and preorbital fossae. The sagittal and occipital crests vary much in development and, though never very prominent, may be quite distinct, very faint, or quite obsolete. The premaxillaries, which differ greatly in length, are yet of a nearly uniform type ; each is composed of three branches, which are almost always- slender and rod-like, but in Hyper- leptus form broad, tapering plates, with minute incisive foramina. The palate is very rugose and between the molariform teeth is strongly con- vex. The mandible has an edentulous beak or spout, which varies remark- EDENTATA OF THE SANTA CRUZ BEDS. 179 ably in length and shape, even in the same genus ; the condyle is set upon a very long, slender neck and this, together with the high coronoid and the very long angular process, gives to this part of the mandible a characteristically trifid appearance. The neck is elongate and slender, with small and rather weak vertebrae. The trunk, and especially the thoracic region, is very long and has numer- ous vertebrae, in some cases at least, as many as 25 ; the loins are short and heavy ; the articular processes in the lumbar and posterior thoracic regions are relatively simple, only one additional pair each of pre- and postzy- gapophyses being present. The tail is stout, but not so massive as in the Planopsidce. Compared with those of the other two families, the limb-bones are rather slender. The manus has very long, compressed and sharp ungual pha- langes, especially on the median three digits. The femur invariably has a prominent third trochanter. The astragalus is relatively long and narrow, moderately or faintly grooved and rarely shows any tendency for the inner condyle to assume the odontoid shape. The calcaneum has a short sus- tentaculum, the astragalar facet of which presents distally and is nearly parallel to the facet for the cuboid, which is large and circular. The pha- langes are heavier than those of the manus, but the unguals are shorter. There is no apparent reason to doubt that the pes was plantigrade and that the entire plantar surface was applied to the ground, unless the partial displacement of the cuboid to the plantar side of the astragalus should be regarded as such a reason. HAPALOPS Ameghino. (Plates XXX-XLV.) Hapahps Amegh.; Enumeracion sistematica, etc., 1887, p. 22. Eucholceops Amegh., in part; Ibid., p. 21. Xyophorus Amegh.; Ibid., p. 23. Parhapalops Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 318. Pseudhapalops Amegh.; Ibid., p. 319. AmpJiihapalops Amegh. ; Ibid., p. 319. Geronops Amegh.; Ibid., p. 320. Eugeronops Amegh.; Ibid., p. 397. Schismotherium Mercerat (non Ameghino) ; Rev. del Museo de La Plata, T. II, 1891, p. 5. l8o PATAGONIAN EXPEDITIONS: PALEONTOLOGY. Stenocephalus Mercerat ; Ibid., p. 10. Tapinotherium Mercerat; Ibid., p. 17. Eurysodon Mercerat; Ibid., p. 18. Eleutherodon Mercerat; Ibid., p. 24. Amarorhynchus Amegh.; fenum. Synopt. de Mamm. Foss. de Patagonie; 1894, p. 147. Mecorhinus Amegh.; Ibid., p. 156. Pseudhapalops Lydekker, in part ; Anales del Museo de La Plata ; T. Ill, 1894, p. 100. As the Megalonychidcz are to the other families of Santa Cruz Gravigrada, so is Hapalops to the other genera of the Megalonychidce, incomparably the most abundant and the most varied ; much more than half of all the ground-sloths contained in the collections of Santa Cruz fossils are refer- able to this genus. Future research may show that the formidable list of synonyms should be reduced, for several of these supposed genera have been established upon fragmentary and uncharacteristic types, and better preserved specimens may prove that more or fewer of them are entitled to generic distinction. There is a remarkable difference of size among the species of Hapalops, ranging from some of the smallest to some of the largest contemporary members of the family, and in the different species, so called, there is the greatest variability in this respect, giving an almost complete series of transitions from one extreme to the other. The dentition is fairly constant and characteristic ; the first tooth in both upper and lower jaws is in the same fore-and-aft line as the other teeth and is isolated by a diastema of varying length ; it is quite small, caniniform and, in most instances, obliquely worn ; in shape it may be cylindrical, obscurely trihedral, or laterally compressed ; - is implanted near the premaxillary suture. The molariform teeth are subquadrate, transversely oval, or faintly trihedral, somewhat as in Megalonyx. The skull is elongate and generally narrow ; the occipital and sagittal crests are never very distinct and may be entirely absent, and in almost all the species the supra-occipital is reflected over upon the roof of the cranium for a considerable distance. The facial part of the maxillary extends beyond - as a thin plate and forms the side wall of the anterior nares, without any thickening of the margin. The premaxillaries vary greatly in length, but are always composed of an anterior, slender branch and two EDENTATA OF THE SANTA CRUZ BEDS. l8l widely separated posterior branches, of which the external one is broader and flatter. The edentulous beak of the mandible varies in correspond- ence with the length of the premaxillaries, but always contracts forward gradually and is not deeply constricted in front of T ; the postero-external opening of the dental canal varies much in position ; it is usually in the ascending ramus, but in several species is in the horizontal ramus at the base of the coronoid. The latter position has been used by Ameghino as the distinguishing mark of Pseud hapalops, but transitions are not wanting, as is shown in the mandible figured in Plate XL, fig. 4, and in text-figure \$, p. 167. The vertebral formula is: C. 7 ; Th. 21-22; L. 3-4; S. 5-6; Cd. ± 20. The neural spines of the trunk-vertebrae are short, straight and, especially in the hinder portion of the trunk, are plate-like and broad antero- posteriorly. The manus does not differ very markedly from that of other contempo- rary members of the family in which the fore-foot is known, its principal characteristic being the elongation of metacarpals IV and V. The femur is broad and much compressed antero-posteriorly and the pes is quite characteristic. Metatarsals IV and V are much longer and more slen- der than II and III and there is an extremely prominent process on the fibular border of the proximal end of V. The species of Hapalops are very numerous, but the problem concern- ing the number and limits of these species cannot be solved with the available material. What has already been said as to the extreme diffi- culty of the taxonomic arrangement of the Santa Cruz Gravigrada applies with particular force to this genus, in which variability is so remarkable. The arrangement adopted in the following pages is to be regarded as merely tentative and subject to revision as more complete specimens are obtained. Relationships. That Hapalops is nearly related to both Nothrothe- rium and Megalonyx is abundantly clear from a cursory examina- tion of the skeleton, all parts of which are very similar to those of the two Pleistocene genera. In fact, there is every reason to believe that Nothrotherium was the direct descendant of some species of this genus. On the other hand it is probable that Megalonyx was derived, not from any Santa Cruz species of Hapalops, but from a closely allied contemporary genus, Megalonychotherium. 1 82 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. HAPALOPS LONGICEPS sp. nov. (Plates XXX-XXXIII.) This is one of the largest known species of this variable genus and is characterized by the great elongation of the rostrum ; the premaxillaries and the edentulous beak of the mandible being much longer than in any other known species. The species is described first, because the type- specimen (No. 15,523) is much the most complete single individual that has yet been found and forms a convenient standard of reference for the other species. Dentition (Plates XXXI, figs. 1,2; XXXII, fig. 2). The teeth dif- fer but little from those of the other representatives of the genus ; - is, as usual, small, caniniform, obscurely trihedral, inserted just behind the maxillo-premaxillary suture and separated from - by a considerable diastema. The other upper teeth (— ) are molariform ; - is subquadrate, with rounded angles; *• is considerably larger and more trihedral, - is more rectangular and - is very small, obliquely worn and without trans- verse valley ; on the posterior face of A is a shallow, vertical groove, which causes a faint bilobation. In the lower jaw T is caniniform, but smaller than - and more erect, rising higher than the other mandibular teeth, and separated from ^ by a shorter diastema than that of the upper jaw ; ^ and ¥ are transverse and rectangular, and their raised margins are quite deeply notched on the inner and outer sides by the transverse valley ; T is subcylindrical, as in most of the other species. MEASUREMENTS. Upper dentition, length • 058 £, width 008 " ^ 035 Lower dentition, length 044 Diastema, length 015 " " " 577 029 1, length (i. e. ant.-post. diameter) 008 Diastema, length 012 " width (i. e. transverse diameter) 007 T, length 006 £, length 007 " width 005 " width oio y, length 0075 *-, length 008 " width 0105 " width oil j, length 0085 A, length 007 " width oio " width 0105 j, length 009 £, length 0055 " width oio Skull (Plates XXXI, XXXIII, fig. i). When seen from the side, the skull is long and low; its upper contour rises quite steeply from the EDENTATA OF THE SANTA CRUZ BEDS. 183 occipital crest to the parietal eminence, which is on a line with the glen- oid cavity ; forward of this, the contour becomes concave at the postor- bital constriction, whence it rises and becomes convex at the frontal sinus, descending again very gradually to the muzzle. The cranium is long and the face short, though much less shortened than in most other species of the genus, a difference due chiefly to the relative development of the pre- maxillae and the mandibular beak, which in the present species are very much as in the Pleistocene genus Nothrotherium (Coelodon). As a whole, the occiput (Plate XXXIII, fig. i) has a shape resembling that of Megalonyx, but is inclined gently backward instead of forward ; it has a broad median vertical prominence, with a broad, shallow fossa on each side of it ; the prominence projects quite strongly above the foramen magnum, making the latter present downward rather than backward. The crest is distinct but not prominent. All the elements of the occiput have coalesced and the sutures are no longer visible, but the shape of these bones may be inferred from a comparison with other species. The basi- occipital is narrower and more convex than in Nothrotheriitm and on its posterior half are two lateral fossae separated by an ill-defined median ridge. The condyles are conspicuously larger than in the Pleistocene genus, but not so widely separated ; they are also broader transversely and taper more to the external ends. The exoccipitals are low and broad, forming relatively little of the occipital surface, and the paroccipital pro- cesses are almost obsolete. The supraoccipital is large and is reflected quite extensively upon the roof of the cranium, between the divergent parietals. The mastoid portion of the periotic is exposed o'n the surface of the skull, but is not demarcated by fossae from the exoccipital and squamosal, as it is in many other species of this genus ; a short but well defined mastoid process is present, with distal facet for the hyoid. As usual, the parietals are very large ; they have no sagittal crest, except near the anterior end, where the crest is very low, but quite distinct. The temporal surface is everywhere convex, in marked contrast to most of the Pleistocene genera, in which this surface is more or less concave. The frontals are long and are made convex by the sinuses, with a moderate depression along the median line ; the postorbital constriction is well marked and in this region the frontals bear the sagittal crest, which is longer than the parietal portion ; the crest does not bifurcate anteriorly 1 84 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. into temporal ridges. No definite postorbital process is formed, but its position is indicated by a small vascular foramen, which differs from that of Nothrotherium in presenting laterally instead of dorsally. The nasal suture is slightly concave, but there is no distinct nasal process. The nasals are narrow and moderately elongate, extending to the anterior rim of the orbit, while in Nothrotherium they excavate the frontals much more deeply and reach almost to the middle of the orbit. These bones are moderately convex in both directions and anteriorly each one is cut by a deep, narrow notch, forming thus a long, slender lateral process, which accompanies the maxillary to the edge of the anterior nares ; the median portion of each nasal is shorter and abruptly truncate at the end, so that the sides of the narial opening extend considerably farther forward than the roof, which is broadly emarginate. In Nothro- therium, on the other hand, the medial portion of the nasal is the longer, extending well beyond the maxillaries. The anterior nares are quite small and rudely semicircular, though somewhat higher than wide. The premaxillaries are strikingly like those of Nothrotherium as fig- ured by Reinhardt ('78, Tab. I, fig. 3) and are therefore very unlike those of the other Pleistocene genera. Each of these bones is Y-shaped and consists of three long and slender branches ; the anterior branch is very unusually elongate, which sharply distinguishes this species from all the other members of the genus ; it extends horizontally forward, ending in a bluntly rounded point and is closely applied to its fellow of the opposite side. Of the two posterior branches, the median one is simply a back- ward continuation of the anterior branch and forms the premaxillary spine, while the lateral branch curves strongly outward and articulates with a shallow depression of the maxillary just in front of the first tooth. The incisive foramina are relatively large, triangular openings, which have an oblique position and are quite widely separated by the spines. The maxillaries are very large and the preorbital portion is relatively shorter and higher than in Nothrotherium, but longer and lower than in the other Pleistocene genera, and ends abruptly in front of the first tooth, with a thin edge ; the alveolus of - forms quite a prominent, curved swelling upon the side of the jaw and between this prominence and the orbit is a deep fossa, which is a very conspicuous feature of the skull, when viewed from above or below. The depth of this fossa varies much in the different species of Hapalops, but is almost obsolete in Nothrotherium, in which EDENTATA OF THE SANTA CRUZ BEDS. 185 the first tooth has been suppressed. The dorsal border of the maxillary is curved, not straight as it is in the last named genus, and the anterior edge is nearly vertical ; between the lachrymal and the nasal the maxil- lary forms a short, transverse suture with the frontal. The alveolar border is straight and nearly horizontal. The palatine processes are long and narrow and in this individual are indistinguishably fused with the palatines and with each other. The hard palate is elongate and narrow, strongly convex and very rugose between the molariform teeth, but be- coming quite flat anteriorly, and everywhere perforated by numerous vas- cular foramina. In the edentulous space there is a well-defined groove on each external side, with raised outer border. The median anterior notch to receive the premaxillary spines is quite small and of a broadly open U- shape. The limits of the palatines cannot be made out. From the analogy of other species it may be inferred that they form little of the hard palate and are extended as large, vertical plates on each side of the posterior nares. The pterygoids are narrow, inconspicuous plates, closely applied to the descending processes of the alisphenoids, and not in the least like the swollen, bulla-like bones of Nothrotherium, which Reinhardt has described ('78, 336). The posterior nares resemble those of the last- named genus in shape, but they are narrower anteriorly, extend farther for- ward, to the line of the last tooth, but not so far backward, and with very different side-walls on account of the different character of the pterygoids and the much larger share taken by the alisphenoids in their formation. The lachrymal is a large, mammillate bone and, carried upon the zygo- matic process of the maxillary, forms a conspicuous prominence on the face and extends dorsally to the frontal. It agrees closely with that of Notlirotherium, but has a larger and more slit-like foramen. The jugal, on the whole, most resembles that of Nothrotherium ; ante- riorly it is expanded and articulates by an apparently movable joint with the maxillary and lachrymal ; the dorsal border of the anterior half of the bone is concave, describing nearly a semicircle and flared outward, to form the rim of the orbit ; the postorbital process is a low and rounded, but distinct angulation, while in the Pleistocene genus there is no trace of it. The postorbital part of the jugal is much longer and more horizon- tal than in the latter ; the suborbital process is a long, laterally com- pressed plate, with convex anterior and concave posterior border, making 1 86 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. it somewhat recurved ; it is narrower than in Nothrotherium, except at the distal end, which has no such emargination of the hinder border. The zygomatic process of the squamosal is also much like that of the Brazilian genus ; it is short, laterally compressed and nearly straight, and projects but moderately from the side of the skull ; its base is inflated by a large sinus and notched by the external auditory meatus ; the glenoid cavity is a large and deep oval pit, without definite postglenoid process. The cranial portion of the squamosal is long and low, extending from the occipital crest to the frontal. The mandible differs strikingly from that of any of the known Pleisto- cene genera. For most of their length, the short horizontal rami are well separated and form a broad jaw, but in front of the teeth they curve sharply inward to the symphysis, where they are completely fused to- gether. The predentary part of the mandible forms an unusually elon- gate, narrow and bluntly pointed spout or beak, with thin and much elevated lateral borders, so that the dorsal surface is deeply concave ; this spout is longer than in any other known species of the genus. The ventral border of the jaw is strongly sinuous, much more so than in Nothrotherium, convex below the teeth and concave behind them, again becoming convex at the angle. Between the first and second teeth the alveolar border is constricted and below this, on the outer side, is a large and deep pit. The coronoid process arises from the outer side of the ramus, leaving a broad groove between itself and the last tooth; it is high, compressed and recurved and shaped much as in Megalonyx. A broad and deep sigmoid notch separates the coronoid from the condyle, which, as in the latter genus, is set upon a long and slender neck ; it is large, hemispherical, with convex dorsal surface and deeply excavated ventral side. The angular process is a very large hook, similar in shape to that of Megalonyx, though longer and narrower; the inflection of the angle, found in all the Santa Cruz Gravigrada, is especially well marked in the present species. As in the last-named genus, the hinder part of the jaw has a trifid appearance, the coronoid, condyle and angle being quite symmetrically placed and of nearly equal lengths, while in Nothro- therium the small angle gives a very different appearance to this part of the jaw. The postero-external opening of the dental canal pierces the ascending ramus above the base. On the left side the foramen is double, doubtless an abnormality. EDENTATA OF THE SANTA CRUZ BEDS. I 87 MEASUREMENTS. Skull, length in median basal line 173 Length, occipital condyle to glenoid Skull, length in median line to anterior cavity 028 border of maxillary 137 Length from occipital condyle to last tooth .077 Skull, extreme length 189 Palate, length in median line (exclusive Cranium, length to anterior rim of orbit .118 of premaxilla) 060 Face, length from orbit to anterior " width at 1 025 ' nares 048 " " " preorbital fossae 028 Face, length from orbit to end of pre- " " "4 017 maxillary 083 " " " £ 013 Occiput, height 047 Mandible, length 140 " width at base 062 " " of predentary beak. . . .049 Cranium, width at postorbital constric- " " from condyle to ^ 065 tion 033 " depth at ^ 028 Cranium, width over lachrymals 065 " thickness at ^ 018 Zygomatic arch, length 090 " height of coronoid 064 Jugal, length of descending process 036 " " " condyle 045 Vertebral Column and Ribs (Plate XXX). — The vertebral column, though well preserved, is not sufficiently complete to show the exact number of vertebrae in each of the different regions, but it is highly probable that the formula was as follows : C. 7 ; Th. 22 ; L. 3 ; S. 6 ; Cd. 20 ±. The neck about equals the skull in length and is quite slender, though relatively heavier than in some of the smaller species. The atlas differs from that of all the Pleistocene genera in which this vertebra is known, and is most like that of Mylodon, but is relatively longer antero-posteriorly, narrower transversely and shallower dorso- ventrally; the anterior cotyles, which are deeply concave, are not so widely separated as in the last-named genus, and between them the in- ferior arch is deeply notched, more so even than in Megatherium; the posterior cotyles are quite large and sessile. The neural arch is thin and but moderately curved and the spine is represented by a very small tubercle ; the foramina for the first pair of spinal nerves are large and per- forate the arch near the anterior border. The inferior arch is narrower and shorter, but thicker and more curved than the neural and has a hypapophysial tubercle ; the large facet for the odontoid process of the axis is continuous with the posterior cotyles. The neural canal is lower and wider than in Mylodon, but ventrally becomes much narrower, and the tubercles for the attachment of the transverse ligament are not con- spicuous. The transverse processes most resemble those of Mylodon, l88 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. having an almost semicircular free border, making the greatest breadth of the vertebra in the middle of its course and not at the hinder border ; in front the processes extend to the border of the anterior cotyles, from which they are separated by notches in the Pleistocene genus ; the hinder margins do not extend beyond the posterior cotyles, as they conspicuously do in Mylodon. The posterior opening of the vertebrarterial canal has a somewhat more forward position than in the latter, in which the foramen is concealed when the vertebra is seen from above ; the canal divides almost immediately, one branch piercing the neural arch and the other passing forward and downward through the transverse process and open- ing on the ventral side ; in front of this ventral opening is another canal which perforates the transverse process obliquely forward and upward. Among the Pleistocene Gravigrada Megalonyx most resembles the pres- ent species in the course of these canals. The axis has a short, wide, depressed centrum, with ventral keel termi- nating in a tubercle on the hinder border, and with transversely oval and very slightly concave posterior face ; the anterior facets for the atlas are relatively larger than in the Pleistocene genera and differ in shape and position, projecting much farther below the centrum and rising less upon the sides of the neural canal. The odontoid process is relatively longer, more slender and pointed than in Mylodon, less so than in Megalonyx, while the neural canal is larger than in any of the Pleistocene genera and the arch wider ; the neural spine is broken away, but was evidently thin. The transverse processes are quite short and slender, more so than those of Megalonyx, which otherwise they resemble ; the vertebrarterial canal is also as in this genus. The other cervical vertebrae are much damaged and the sixth and seventh have been lost. The third vertebra is considerably smaller than the axis ; the centrum is depressed and oblique, with transversely oval faces, is slightly opisthoccelous and has a well-defined ventral keel. The pedicles of the neural arch are low, but the arch itself is broad and is flattened on the dorsal side ; the zygapophyses are large, especially the anterior pair. The spine and transverse processes are missing. The fourth cervical is like the third, but it is somewhat smaller and has a less prominent keel ; the transverse process is a slender rod, extended in the fore-and-aft direction and perforated at the base. The fifth is slightly smaller than the fourth. EDENTATA OF THE SANTA CRUZ BEDS. 189 Though several thoracic vertebrae have been lost from this skeleton, other species of the same genus indicate that the number was twenty-one or twenty-two. In the anterior part of the thorax the vertebrae have small centra, very broad neural arches and short, heavy spines, which incline backward, are thickened and rugose at the free ends, and so broad that hardly any intervals appear between the successive spines. The contrast in length between these short spines and the elongate processes of the great Pampean genera is very striking. Posteriorly, the centra become larger, especially in width, and on the ventral side of the penultimate thoracic are two small foramina, which on the last one become large and conspicuous ; the transverse processes gradually shorten and have a more elevated position, arising from the neural arch rather than the centrum ; the neural spines are somewhat shorter and less inclined, but broader and thicker. The accessory articular processes are not very well preserved, but seem to agree perfectly with those of other species of Hapalops and to consist of only one additional pair each of pre- and of post-zyga- pophyses. In this individual are three lumbar vertebrae, which closely resemble the last two or three thoracics, but are larger ; the centra are very broad and depressed, increasing in width posteriorly. The ventral foramina are very conspicuous, though this was a rather aged animal, with epiphyses united to the centra. The neural spines are broad and much thickened at the tip, but short and nearly erect ; the transverse processes are rather short, but very broad, depressed, plate-like and curved forward. Apparently the sacrum consists of six vertebrae, of which the first may be a lumbar, for its centrum is still separate from the others, though the spine is fused with the common ridge. In the middle part of the sacrum the centra become very thin and depressed, increasing again in thickness posteriorly. The ilia articulate with the first three, or perhaps, four ver- tebrae and the ischia with the last two. Of the caudal vertebrae, nine are preserved, the first four in their natural position. Evidently, the tail was very stout, but not very long, and the number of vertebrae was probably not much more or less than twenty. The first caudal is large and massive and might easily be mistaken for the lumbar of a smaller animal ; the centrum is short, broad and somewhat depressed, with transversely oval, nearly plane faces, and on the ventral side two parallel ridges, which bear facets for the first chevron-bone ; the 190 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. neural arch and canal are low and wide and the spine is heavy and quite prominent ; the zygapophyses, especially the anterior pair, are very large, projecting in front of and behind the centrum, while the metapophyses are low and rugose ; the transverse processes are long, broad and quite thick. The second, third and fourth caudals resemble the first and their centra are of nearly the same length, but grow narrower and thinner pos- teriorly, while the facets for the chevron-bones are more prominent, en- closing a deeper groove, and all the other processes are reduced. The third vertebra closely resembles the anterior caudal of Nothrotherium figured by Reinhardt ('78, Tab. II, figs. 4, 5). Next, after an interval, follows a group of four vertebrae, which may be provisionally called the seventh, eighth, ninth and tenth. In these the centra have become cylindrical and the chevron-facets are even more prominent ; these facets are no longer continuous ridges, but are separated by deep notches into anterior and posterior portions ; from the notch on each side a well-defined groove passes up to the hinder border of the transverse processes; the latter are short, but quite broad; the neural canal is very small, especially on the ninth (?), which has no spine. Lastly, there is an isolated vertebra, probably the twelfth or thirteenth caudal, in which the neural canal is hardly more than a pin-hole, the chevron-facets are much less prominent and the grooves almost obsolete. The only chevron-bone preserved is that attached to the first and sec- ond caudals; this is short and Y-shaped, broad antero-posteriorly and thickened to form the vertebral facets ; the distal, undivided portion is short and narrow, ending in a tubercle. MEASUREMENTS. Atlas, an tero -posterior length 031 Anterior thoracic, length of centrum. . . .023 " width 078 " " width of anterior face .017 " height, dorso-ventral 032 " " " " posterior face .020 Axis, length of centrum • 034 Anterior thoracic, width over transverse " width of anterior face 035 processes 067 " " " posterior face 028 Anterior thoracic, height of neural spine Third cervical, length of centrum 024 above centrum 046 " " width of anterior face . . .022 Anterior thoracic, width of neural spine " " " " posterior face . . .020 at tip 020 Fourth cervical, length of centrum 025 First lumbar, length of centrum 032 " " width of anterior face . .020 " " width of anterior face 037 " " " " posterior face .019 EDENTATA OF THE SANTA CRUZ BEDS. 191 First lumbar, width over transverse pro- cesses 075 First lumbar, height of neural spine . . . .036 First lumbar, width of neural spine at tip 030 Third lumbar, length 030 " " width of anterior face. . . .039 Sacrum, length 7185 Sacrum, width 01 anterior face of centrum .045 " " " posterior face 030 First caudal, length of centrum 026 " " width of anterior face 034 First caudal, width over transverse pro- cesses 115 Second caudal, length of centrum. .... .025 " " width of anterior face . . .032 Second caudal, width over transverse processes 084 Third caudal, length of centrum 024 Third caudal, width of anterior face 027 Third caudal, width over transverse pro- cesses 685 Fourth caudal, length 025 " " width of anterior face . . .030 Fourth caudual, width over transverse processes 082 ? Seventh caudal, length 024 " " width of anterior face . .024 ? Seventh caudal, width over transverse processes 062 ? Eighth caudal, length 024 " " width of anterior face . . .020 ? Ninth caudal, length 023 ? Eleventh caudal, length 020 " " width of anterior face .020 ? Eleventh caudal, width over transverse processes' 048 ? Thirteenth caudal, length 020 Compared with those of the other species of the genus, the ribs of H. longiceps are decidedly broader and heavier, though they are much more slender than those of the great Pleistocene genera. The vertebral ribs are long and quite strongly curved, forming a capacious thorax. The head of each rib is rather broad, much depressed dorso-ventrally ; the neck is elon- gate especially in the middle region of the thorax, and the tubercle is large, but flat and nearly sessile. A remnant of the tubercle is present on the penultimate rib, but not on the last one, which is very much shorter and more slender than the former. The sternal ribs are fully ossified, but their state of preservation is such that little can be determined concerning their shape and number. Of the sternum nothing remains. Appendicular Skeleton. — Only the distal portion of the scapula is pre- served and in a much damaged condition ; apparently there were no im- portant differences from that of the other species. The slender, elongate humerus ( Plate XXX, figs. 2, 2a ) is markedly similar to that of Megalonyx and Notkrothermm. The head is small and hemispherical and is set upon a rather more distinct neck than in the for- mer ; the tuberosities are better developed than in either of the genera named, especially the external one, which gives the bicipital groove a posi- tion on the inner side of the head, instead of opposite its middle. In the PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. length and slenderness of the shaft there is a close resemblance to Megalonyx, but a likeness to Mylodon is seen in the great development of the deltoid ridge, which is far larger than in the former, but in spite of this great development, the " musculo-spiral course" is even less distinct than in Megalonyx (Leidy, '55, PI. IX, fig. 2) ; the pectoral ridge is not conspic- uous. For most of its length the shaft is irregularly cylindrical, and is greatly broadened and antero-posteriorly compressed distally, though relatively less so than in Megalonyx, while the very prominent and mas- sive internal epicondyle is larger and the external smaller than in the latter, and the bony bridge over the epicondylar foramen is broader. The trochlea is wider than in the last-named genus, with much larger, sphe- roidal radial facet and slightly concave ulnar surface. The anconeal fossa is small and shallow, as in Mylodon; in Megalonyx it is obsolete. In their proportions and general appearance the forearm bones most resemble those of Megalonyx, though having a certain resemblance to those of Megatherium ; the extremely short and massive bones of Mylo- don are entirely different. The ulna (Plate XXXII, fig. 4) is moderately elongate and has a short olecranon, which, however, is relatively longer than in Megalonyx or Nothrotherium ; in shape it most resembles the olecranon of the former genus, but has no such transverse broadening of the proximal end ; the coronoid process is more prominent and the sig- moid notch more nearly approximates the arc of a circle in form ; the humeral facet is narrow and its internal division is much more produced distally than in the two Pleistocene genera ; the facet for the head of the radius is small and nearly plane. The shaft is short, laterally compressed, and somewhat curved ; the outer surface is deeply grooved, while the inner has only a shallow channel near the proximal end ; the distal end is con- tracted and bears a small, oblique facet for the pyramidal. The radius (Plate XXXII, fig. 3) is shaped much as in Megatherium, but with more decided antero-posterior and lateral curvature, and the more oval and projecting head gives it a less abruptly truncated appear- ance ; the humeral facet is quite deeply concave and the proximal surface for the ulna is very narrow transversely and confined to the posterior side of the head. The shaft is strongly curved and has a convex anterior and concave posterior surface ; its proximal portion is of transversely oval sec- tion, the breadth not greatly exceeding the thickness ; below this the shaft broadens abruptly, the internal border becoming a thin edge, and con- EDENTATA OF THE SANTA CRUZ BEDS. 193 tinues to widen to the distal end ; the ulnar border describes a regular, slightly concave curve, beginning below the bicipital tubercle, which is large, prominent and rugose, placed well below the head and on the pos- terior side of the shaft. The distal end of the radius is moderately wide and thick and has a large, low tuberosity on the dorsal face ; the carpal surface is concave, undivided and oblique to the shaft, descending to the styloid process. The manus (Plate XXXIII, fig. 2) is much less specialized than in any of the known Pleistocene genera, most resembling that of Megalonyx. All of the carpal elements are separate from one another. The scaphoid is very short proximo-distally, but very broad ; on the ulnar border it is thick, but contracts much to the radial side, where it is extended into a blunt, hook-like and slightly recurved process ; the radial facet is reflected far over upon the dorsal face, extending to and making a sharp angle with the surface for the trapezoid ; on the distal end are large facets for the trapezium and trapezoid and, on the palmar side, one for the lunar also ; contact with the magnum is extremely limited, while in Megalonyx it is quite extensive. The lunar is large and shaped quite as in Nothrotherium, but with the radial facet much more extended upon the dorsal side. On the palmar side the lunar extends beneath the scaphoid and on the ulnar side has a very large, deeply concave facet for the pyramidal ; distally, the lunar rests entirely upon the magnum and has no contact with the unciform. The pyramidal is large and of irregularly cubical shape ; it is longer proximo-distally than the scaphoid or lunar, but diminishes toward the ulnar border ; the ulnar facet is large, somewhat saddle-shaped and forms almost a right angle with the surface for the pisiform, which is entirely palmar ; on the radial side the pyramidal extends beneath the lunar, much as in Megalonyx. The pisiform is large and laterally compressed, and somewhat resem- bles that of Megalonyx, but is of more nearly circular form. As in Nothrotherium, the trapezium is free, while in the other Pleisto- cene genera it is fused with the scaphoid ; it is long, very narrow and thick, and distally articulates only with metacarpal II. When placed in its natural position, the obliquity of the trapezium is such as to suggest that the pollex diverged considerably from the other digits. 194 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. The trapezoid is shorter than the trapezium, but otherwise quite large, and on the dorsal side is broad, contracting to a blunt edge on the pal- mar ; the proximal end articulates with the scaphoid by a saddle-shaped facet, while the distal end is modelled to fit the curiously complex end of metacarpal II. The magnum 'is rather small and narrow and but slightly longer than the trapezoid ; proximally it is covered by the lunar, but the thin and elevated radial border is wedged in between the lunar and the scaphoid ; distally the magnum articulates only with metacarpal III. The unciform is large ; on the dorsal side it is both broad and long, but on the palmar side contracts to a blunt point, though without forming a distinct palmar hook ; the contact with the lunar, if present, must be very small and entirely lateral ; the distal end articulates with metacarpal III, which notches it in a curious way, and with metacarpals IV and V, the facet for the latter rising on the ulnar side almost to the proximal end. The metacarpus consists of five members, which are straight and have no such appearance of torsion as those of the Pleistocene Gravigrada and the recent ant-bear, the manus having the appearance of a plantigrade unguiculate. Metacarpal I has been lost from this specimen, but in other species of Hapalops it has much the shape and relative size of that of Nothro- therium. Metacarpal II is proportionately shorter and heavier than in the latter, longer and more slender than in Megalonyx ; the proximal end, which is slightly wider than the shaft, has a large facet on each side for the ad- joining metacarpals, but is connected only with the trapezoid, the facet for which is very complex, forming a deep groove on the radial and a plane surface on the ulnar side ; the shaft is short, stout, slightly curved and of irregularly quadrate section, broadening and thickening slightly to the distal end ; the carina is exceedingly prominent and the rest of the trochlea consists of a narrow surface on each side of it. Metacarpal III has much the same shape as in Megalonyx, while in Nothrotherium it is longer and much more slender ; the proximal end is very broad and has five different facets, for metacarpal II, the magnum, two for the unciform and one for metacarpal IV ; the magnum surface is a narrow groove ; the shaft is short and stout, much broader than any of the other metacarpals, and in its proportions is intermediate between meta- EDENTATA OF THE SANTA CRUZ BEDS. 195 carpal III of Megalonyx and that of Nothrotherium, longer and more slender than in the former, shorter and heavier than in the latter; the distal end bears a narrow trochlea, with immensely developed keel. Metacarpal IV is the longest of the series and relatively much longer than in any of the Pleistocene genera, except Nothrotherium, in which it is even more elongate ; the proximal end is moderately expanded trans- versely and palmo-dorsally, with facets for the unciform and for metacar- pals III and V; the shaft is laterally compressed and slender, of quadrate section, but with convex dorsal surface, not flat or concave as in metacar- pals II and III, with straighter lateral borders than in Megalonyx and without any such dorsal ridge ; the distal end also is narrower than in the latter. Metacarpal V also resembles that of Megalonyx, but is relatively longer and lighter ; in length it is inferior only to metacarpal IV and is more slender than any other, with the probable exception of metacarpal I ; the projection from the ulnar side of the proximal end is far less prominent and massive than in Megalonyx ; the proximal end articulates with the unciform by a facet which is oblique and almost lateral, but does not reach the pyramidal ; the shaft is very slender and somewhat curved, with decidedly concave ulnar border, and is of subcircular section ; the distal end is small and club-shaped. The phalanges are of similar shape in all of the digits, but with cer- tain modifications in each one ; on the whole, they most resemble those of Megalonyx, while in Nothrotherium they are peculiarly differentiated. The proximal phalanx is very short, though relatively longer than in the Pleistocene genera, the length slightly exceeding the width and being much surpassed by the dorso-palmar thickness. In shape this phalanx best agrees with that of Megalonyx, but its proximal end is rela- tively less thickened ; the proximal and distal surfaces are much alike, each having a very deep median groove ; in Nothrotherium these grooves notch the dorsal face much more deeply and are separated only by a nar- row bridge of bone. This phalanx is largest in digit III, smallest in V, and slightly larger in II than in IV. The second phalanx is very much longer and narrower than the first and has the proximal end much thicker palmo-dorsally than the distal, though the difference is rather less decided than in Megalonyx; the proximal trochlea has two concave facets, separated by a prominent median ridge, 196 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. which on the dorsal side becomes a conspicuous beak ; the distal trochlea is extensively reflected upon both dorsal and palmar faces and describes somewhat more than half a circle ; it consists of two rounded ridges, with a median groove between them ; on the dorsal side of the phalanx, above the distal trochlea, is a deep pit for the beak of the ungual. The second phalanx is of nearly the same length in digits II, III and IV, but is heaviest in III ; in digit V it is much shorter and more slender and the distal trochlea is reduced. The ungual phalanges, which differ only in size in the various digits, quite closely resemble those of Megalonyx, being very long, compressed, decurved and sharply pointed, with a shallow cleft at the tip ; the bony hood at the base of the claw has much the same relative development as in the latter, and the subungual process is similar, but somewhat nar- rower, and is pierced by two vascular foramina ; the proximal end is very deeply incised to form a trochlea for the second phalanx and the dorsal border is drawn out into a broad, blunt beak. In the pollex the ungual is less reduced than that of Megalonyx, and in the three median digits is very large, longest in III and somewhat shorter in II than in IV ; in V it is much smaller. In length, the three median digits much surpass the laterals I and V, and are of nearly equal lengths, the phalanges compensating for the dif- ferences in the metacarpals. Thus, the longest digit is III, which is due to the size of the ungual, while the larger ungual of II makes it nearly as long as IV despite its much shorter metacarpal. In order of length the digits are as follows : III, IV, II, V, I. In actual length there is hardly any difference between digits III and IV, but the position of the former with reference to the carpus makes it appear to be considerably longer. MEASUREMENTS. Scapula, breadth distal end over coracoid .068 Radius, width of proximal end 025 Scapula, anterior-posterior diameter of " " " distal end 030 glenoid cavity 03 2 Carpus, length in median line 030 Humerus, length from head 192 " width . . .- 059 " width of trochlea 044 Metacarpal II, length 038 " " over epicondyle 079 " " width of proximal end .016 Ulna, length 197 " " " " distal end 013 " " of olecranon 035 Metacarpal III, length 038 " width at sigmoid notch 028 " " width of proximal end .. .023 Radius, length 165 " " " " distal end 016 EDENTATA OF THE SANTA CRUZ BEDS. 197 Metacarpal IV, length 049 " " width of proximal end .013 " " " " distal end 014 Metacarpal V, length 043 " " width of proximal end .. .on " " " distal end 007 First phalanx, digit II, length 016 " " " III, length 017 First phalanx, digit III, width of proxi- mal end 016 First phalanx, digit III, thickness of proximal end 020 First phalanx, digit IV, length 015 First phalanx, digit IV, width of proxi- mal end 014 First phalanx, digit IV, thickness of proximal end 02 1 First phalanx, digit V, length 009 First phalanx, digit V, width of proxi- mal end 009 First phalanx, digit V, thickness of proxi- mal end OI2 Second phalanx, digit II, length 027 Second phalanx, digit II, width of proximal end 012 Second phalanx, digit II, thickness of proximal end 016 Second phalanx, digit III, length 025 Second phalanx, digit III, width of proximal end 015 Second phalanx, digit III, thickness of proximal end 020 Second phalanx, digit IV, length 0235 Second phalanx, digit IV, width of proximal end 0115 Second phalanx, digit IV, thickness of proximal end 017 Second phalanx, digit V, length 013 Second phalanx, digit V, width of proximal end 008 Second phalanx, digit V, thickness of proximal end oio Ungual, digit I, length 032 " " " width of proximal end .010 Ungual, digit I, thickness of proximal end 012 Ungual, digit II, length 050 " " " width of proximal end .012 Ungual, digit II, thickness of proximal end 017 Ungual, digit III, length 057 " " " width of proximal end .014 Ungual, digit III, thickness of proximal end 020 Ungual, digit IV, length 047 " " " width of proximal end .oil Ungual, digit IV, thickness of proximal end 019 Digit I, length (approx) 060 "II, " 104 " III, " 112 "IV, " no " V, " (approx.) 080 The pelvis differs notably from that of the large Pleistocene genera and has a certain resemblance to that of Bradypus; most of its length and width are made up of the ilia, the ischia being much smaller. The ilium has a broad, depressed and very short peduncle, the sacral surface extending back almost to the level of the acetabulum ; anteriorly the ilium reaches considerably beyond the sacrum and partially conceals the second lumbar vertebra, when viewed from the side ; the anterior plate is broad and flat, with acetabular border external, making the gluteal surface dorsal and the iliac surface ventral, even more strictly so than in Bradypus ; the acetabular border describes a considerable curve, with the concavity turned 198 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. outward ; the gluteal surface is moderately concave and the iliac crest somewhat thickened and rugose. In the huge Gravigrada of the Pleisto- cene the ilia are immensely expanded and everted, making the gluteal surface posterior rather than dorsal and the iliac surface anterior rather than ventral, while the crista is enormously thick. However, the difference from the Santa Cruz type of pelvis, obvious as it is, is not at all fundamental, for the great expansion and eversion of the ilia occur in many unrelated groups of very large terrestrial mammals, such as the elephants, the titano- theres, etc., and the change. in the form of the pelvis from the Santa Cruz to the Pleistocene ground-sloths is strictly analogous to that between Palceosyops and Titanotherium. The ischium is much shorter than the ilium, but the disproportion is not so great as in Bradypus ; it is depressed and broad, especially behind, where it is ankylosed with the transverse processes of the last two sacral vertebrae ; the sacro-sciatic foramen is quite small, but relatively larger than in Mylodon, and the tuberosity is larger and more prominent than in the latter. The pubis is slender and laterally compressed, expanding somewhat at the distal end, where it forms a short symphysis ; it is rela- tively much shorter than in Mylodon and the pelvic opening is conse- quently smaller, especially in the dorso-ventral diameter; the obturator foramen has approximately the shape of an equilateral triangle. The acetabulum presents directly outward and is of elongate oval shape ; the articular surface is quite narrow, because of the very large sulcus for the round ligament. MEASUREMENTS. Pelvis, length 262 Ilium, greatest width 108 " greatest width 340 Ischium, length 101 Ilium, length 161 Acetabulum, antero-posterior diameter. .050 The femur (Plate XXXII, fig. 5) resembles that of Nothrotherium in its proportions. The head is small and set upon a distinct neck and it presents more directly inward, less upward than in Megalonyx, and rises very little above the great trochanter ; the pit for the round ligament is a shallow, pyriform depression and is entirely enclosed in the articular sur- face. The great trochanter is a heavy, rugged mass, which rises higher proximally than in the Pleistocene genera ; the digital fossa is very small, but not so much reduced as in Megalonyx ; the second trochanter is more prominent than in the latter, but less rugose and less extended distally, EDENTATA OF THE SANTA CRUZ BEDS. 199 while the third trochanter is much larger and more prominent than in Megalonyx or Nothrotheritim, the only Pleistocene genera in which this process is retained. The shaft is intermediate in character between the two genera named, being somewhat broader and more flattened than in the latter, less so than in the former ; it is also relatively longer than in Megalonyx, considerably exceeding the humerus in length, while in the Pleistocene genus the two bones are nearly equal ; the anterior or dorsal face of the shaft is slightly convex and its proximal half bears two long, parallel ridges for muscular attachment, which are less prominent than in the last-named genus. The tuberosities are prominent, and the external one is large and rugged, while the inner one is quite small. The rotular groove is somewhat narrower than in Megalonyx and is extended much farther upon the dorsal face of the shaft, with its proximal end distinctly projecting from the shaft, which has an obscurely marked suprapatellar fossa. The condyles are small and present so directly backward as to be concealed when the femur is viewed from the front ; the inner condyle is considerably the larger of the two, being more prominent and more con- vex, while the outer one is slightly concave transversely ; the intercondylar notch is narrower than in Nothrotherium. On the proximal side of each condyle is a small facet for the flabellae, which are large, irregular nodules of bone. The patella (Plate XXXII, fig. 6, 6a) is most like that of Megalonyx, a broad, shield-shaped bone, covered on the dorsal side with irregular lon- gitudinal ridges, which give it a wrinkled appearance ; its distal portion is more prolonged and ends in a much sharper point, while the articular sur- face for the rotular groove, which is very slightly convex, has a relatively greater proximo-distal extension. In its proportions the tibia (Plate XXXIII, fig. 3, 3*2) is intermediate between that of Nothrotherium and that of Megalonyx ; it is considerably shorter than the femur, and in relation to that bone is somewhat shorter than in the former genus, longer and with narrower, less antero-posteriorly compressed proximal end than in the latter; the facets for the femoral condyles are separated only.by a narrow sulcus and the inner one is larger and more concave and stands at a lower level than the outer, which is convex and produced farther behind the plane of the shaft, though it has no such extension as in Megalonyx, and the fibular facet is a longer, nar- rower oval. The shaft is relatively longer, narrower and thicker than in 2OO PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. the last-named genus and its fibular border is far less concave ; the proxi- mal portion of the shaft is subtrihedral and the distal part is broad and antero-posteriorly compressed, but for most of its length is of irregularly oval section ; the cnemial process is very inconspicuous. The distal end is much like that of Nothrotherium, but the conspicuous process, grooved by a tendinal sulcus, which projects from the inner side (see Plate XXXIII, fig. 3#), is more prominent than in that genus or in Megalonyx, and the inner malleolus is less reduced than in the latter. The astragalar surface has two shallow facets divided by a low intercondylar ridge, which, on the dorsal border becomes a tongue-like process ; the external astragalar facet is continuous with that for the distal end of the fibula ; the latter surface presents distally rather than laterally, as is also true of both the Pleisto- cene genera. The fibula (Plate XXXIII, fig. 3, 30), though short and stout, is rela- tively much longer and more slender proportionally than in Mylodon; the proximal end is thick and club-like and bears an elongate, narrow facet for the tibia; the shaft is irregularly cylindrical and the distal end much enlarged and very massive. MEASUREMENTS. Femur, length from head 212 " " " great trochanter. .. .218 " width of proximal end 084 Femur, width of distal end over tuber- osities 076 Femur, width of rotular groove 026 " " over condyles 066 Patella, length 041 " width 037 Tibia, length 163 " width of proximal end1 062 " thickness of proximal end 057 Tibia, width of shaft in middle 02 1 " thickness of shaft in middle 028 " width of distal end 055 " thickness of distal end 028 Fibula, length 155 " width of proximal end 020 " thickness of proximal end 029 " width of shaft in middle oio " thickness of shaft in middle 014 " width of distal end 023 " thickness of distal end 030 The pes (Plate XXXII, fig. 4) belongs to the type of Megalonyx and Nothrotherium, both of which it resembles. The astragalus is much like that of the former genus, but somewhat longer and narrower ; the trochlea is much more deeply grooved and is quite distinctly divided into inner and outer condyles, of which the internal one is much larger both in the proximo-distal and dorso-plantar diameters ; at the distal end the trochlea 1 Reduced by lateral crushing. EDENTATA OF THE SANTA CRUZ BEDS. 2OI is invaded by a narrow V-shaped sulcus, which ends in a deep pit on the neck for the reception of the tongue-like process of the tibia ; the fibular facet is large and crescentic, as in Megalonyx, but with much more con- cave plantar border, narrower proximal portion and much less prominent everted process at the distal end. The external calcaneal facet is some- what narrower than in Megalonyx, but much more concave and more oblique to the proximo-distal axis, while the facet for the sustentaculum is less distal and more internal in position and is separated from the outer facet by a narrower sulcus. The neck is much shorter than in Nothrotherium and even somewhat shorter than in Megalonyx, but has a navicular facet like that of the latter, concave at the distal end and reflected well over upon the tibial side. An important difference from the last-named genus is in the position of the cuboid facet, which is a convexity on the plantar side of the neck, while in the Pleistocene genus it is on the fibular side. In the astragalus of Nothrotherium the most striking difference from that of Hapalops is the much longer neck, which is constricted by a deep notch on each side, ending in a convex head. The calcaneum also resembles that of Megalonyx, which Leidy de- scribes as "having very much the appearance of the os ilium of some smaller animal" ('55, 41). The tuber is long, but much less elongate and with a far less slender neck than in the two Pleistocene genera, expanding much more abruptly into a very broad, depressed, falcate plate, which has a longer tibial than fibular border, while the proximal border is much thickened and rugose, with prominent tubercles on the plantar side ; the distal end is very heavy, with a great prominence on the fibular side. A number of differences from the calcaneum of Nothro- therium may be observed in the distal portion ; the external astragalar facet is smaller, more simply convex and less reflected upon the dorsal side; the sustentaculum is smaller and its facet is smaller and more distal, less dorsal ; the cuboid surface is more oval. The navicular quite closely resembles that of Megalonyx, but is more nearly circular and the low convexity on the proximal face, which fits into the distal end of the astragalus, is less prominent; on the tibial side the border is much raised, so that the proximo-distal length on this side is more than twice as great as on the fibular; the large, convex facets for the meso- and ectocuneiforms are more closely approximated than in the Pleistocene genus, while that for the entocuneiform is entirely lateral. 202 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. The entocuneiform has been lost from the specimen. The mesocuneiform is broad and extremely short proximo-distally, and is much less extended in the dorso-plantar dimension than the ectocuneiform. The latter is quite large, especially on the dorsal side, tapering to a blunt point on the plantar ; the distal end is wedge-shaped and fits into the deep groove on the head of metatarsal III. The cuboid is rather small, relatively narrower and more pyramidal than in Megalonyx, and is so placed in the tarsus that its long axis is oblique to that of the calcaneum and astragalus, and it lies partially upon the plantar side of the neck of the astragalus, to which it affords consider- able support. The calcaneal facet forms a prominent convexity on the fibular side and that for the astragalus is large, slightly concave and dorsal in position, the two surfaces meeting at the proximal end, to which they give a wedge-like shape. Distally, the facet for metatarsal IV is very large and that for V is very narrow, much narrower than in Megalonyx. A large plantar sesamoid is preserved in connection with this pes ; it is flattened and scale-like, but quite thick and heavy and of an irregularly pentagonal shape with rounded angles, and its principal diameter is trans- verse. This sesamoid is placed upon the plantar side of the cuneiforms, extending under metatarsals I and II. The five metatarsals are strikingly like those of Megalonyx and Nothrotherium, with somewhat closer resemblance to ' the latter. As in both of the genera named, the three inner members (I-III) are very short and the two outer ones (IV, V) much longer. Metatarsal I is short and slender, far more so than in Nothrotherium, in which this bone is very stout ; the facet for the entocuneiform is large and saddle-shaped, the shaft very short and subcylindrical and the distal carina very low. Metatarsal II is much larger in all its dimensions than I and is rela- tively shorter and heavier than in Nothrotherium, much more slender than in Megalonyx ; the broad proximal end has a transversely concave surface for the mesocuneiform ; the shaft is very heavy and the distal trochlea is very large with heavy, prominent carina. Metatarsal III is much the most massive of the series and, except I, the shortest ; its length slightly exceeds the breadth, while in both of the Pleistocene genera the breadth exceeds the length ; the two sides of the EDENTATA OF THE SANTA CRUZ BEDS. 203 facet for the ectocuneiform meet at an obtuse angle and on the fibular side of the head is a very large plane surface for the fourth metatarsal ; the broad distal trochlea has a very prominent and thick carina, which, however, does not attain such proportions as in Megalonyx. Metatarsal IV is in very striking contrast to III, being more than twice as long and very much more slender; it is relatively longer, straighter and of more regular shape than in Megalonyx and has more nearly the proportions of Nothrotherium ; the proximal end is narrow and of great dorso-plantar thickness and bears an oblique facet for the cuboid, and extensive lateral facets for the adjacent metatarsals, and the relative posi- tion of these three facets is such that the bone is given a strongly diverg- ent direction, as in Nothrotheriiim ; the shaft is relatively slender and elongate, almost straight and of subquadrate section with rounded angles ; the trochlea is narrow, not much wider than the shaft, but very thick and with very prominent carina. Metatarsal V has much the same characteristics as in Nothrotherium and Megalonyx ; the cuboid facet is very much narrower than in those genera, especially the latter ; the shaft is depressed and shorter than that of IV and gives off from the fibular side near the proximal end a very large, triangular process, which is unfortunately broken, but was doubtless shaped as in other species of Hapalops and very similar to that of Nothro- thermm; the distal trochlea is quite different from that of II, III and IV, being merely an elliptical convexity, without carina. The phalanges are very much like those of the manus, but considerably shorter, and those of digits II and III are much heavier. The first pha- lanx of the hallux is relatively long, laterally compressed and slender; its proximal trochlea is deeply concave and but feebly grooved for the carina ; near the distal end is a deep dorsal pit to receive the beak of the ungual. In digit II the first phalanx is short, wide and very thick, especially at the proximal end, and both trochleae are very deeply grooved in the median line, while in digit IV it is of nearly the same size as in II. All the phalanges of the fifth digit have been lost. The second phalanx is like that of the manus in form, but in digits II and III, at least, it is very much heavier. In the second digit this phalanx is moderately elongate, though attaining no such length as it has in Nothrotherium, and in the third it is very short and ex- tremely heavy. 2O4 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. The ungual phalanx of the hallux is considerably shorter than that of the pollex, but broader and thicker. Digit II has a very much larger ungual, which is shorter and more massive and is more strongly decurved than the corresponding claw in the manus, and the distal cleft is more extended along the dorsal border. The third digit has a still longer and heavier ungual, the proximal end of which is extremely massive ; owing chiefly to the size of this ungual, digit III is considerably longer than II, though the difference is decidedly less than in Nothrotherium. As a whole, the pes is considerably larger than the manus, especially exceeding the latter in the massiveness of its component parts. MEASUREMENTS. Calcaneum, length 075 width of proximal end 065 " " " distal end 038 Astragalus, length 042 " width of trochlea 029 " " distal end 023 " thickness of distal end 016 Navicular, length on tibial side 016 " fibular side 005 " width 026 Metatarsal I, length 020 " proximal width oio " distal width 008 Metatarsal II, length 025 " " proximal width 017 " " " thickness 016 " " distal width 015 " " " thickness 020 Metatarsal III, length 026 " proximal width 023 thickness 027 " " distal width 017 " " " thickness 023 Metatarsal IV, length 055 " " proximal width 014 " " " thickness 025 " " distal width 014 " " " thickness 023 Metatarsal V, length 045 " " proximal width ? .027 " " " thickness 017 Metatarsal V, distal width 013 " " " thickness 014 First phalanx, digit I, length 019 " " " " proximal width.. .010 " " " " thickness. .0135 " " " " distal thickness . .0085 First phalanx, digit II, length 016 " " " " proximal width. .013 " " " " proximal thick- ness 019 " " " " distal thickness. .013 " " " III, length 019 " " " " proximal width. .017 " " " proximal thick- ness 028 " " " " distal thickness. .017 " " IV, length 016 " " " " proximal width. .012 "•' " proximal thick- ness 022 " " " " distal thickness. .015 Second phalanx, digit II, length 026 " " proximal width. .013 " " proximal thick- ness 018 " " " " distal thickness. .012 " III, length 022 " " proximal width. .018 " " proximal thick- ness 024 " " distal thickness. .015 EDENTATA OF THE SANTA CRUZ BEDS. 205 Ungual, digit I, length 026 Ungual, digit III, length 060 " " " proximal width on " " " proximal width 020 " " thickness 015 " " " " thickness... .028 " " II, length 049 Digit I, length 057 " " " proximal width 013 " II, " 097 " " " thickness . . . .018 " III, " 102 Restoration (Plate XXX). As there is no available material for a resto- ration of Megalonyx or Notkrotherium, Owen's well-known figure of My- lodon ('42, PI. I) has been selected as a standard of comparison and the skeleton of H. longiceps has been drawn in a similar attitude. Between the Santa Cruz and the Pampean genus the contrasts are much more numerous and striking than the resemblances. In the former the head is relatively small, with elongate rostrum, slender, rod-like premaxillaries and long, pointed mandibular beak; the neck is long and light, and the trunk, especially the thoracic region, is extraordinarily elongate, a very marked difference from the rather short and extremely bulky trunk of Mylodon; the neural spines of all the trunk-vertebrae are far shorter than in the latter ; the tail, though heavy, is not nearly so massive. The pelvis has a very different appearance, owing to the much less extreme ex- pansion, eversion and rotation of the ilia and to the shorter pubes and descending processes of the ischia. The limbs are far more slender than in Mylodon, the feet pentadactyl and very little modified, all the digits being functional and provided with claws ; although the manus may have already acquired, in an incipient degree, the rotation which brought the ulnar border to rest upon the ground in walking, it is probable that the pes was simply plantigrade. On the other hand, this skeleton has a number of suggestive resem- blances to that of the recent Tardigrada. In making such a comparison, it should be remembered that the latter are extremely specialized and adapted to a very unusual mode of life ; the whole skeleton is modified in accordance with the habit of suspending the weight of the body and the feet are transformed into mere hooks. In spite of such mechanical differences between the strictly arboreal Tardigrada and the doubtless as strictly terrestrial Gravigrada, there is much to suggest a common origin of the two groups, and these correspondences are particularly clear in the skel- eton before us. The type of skull and dentition is essentially the same, and the extremely elongated trunk is very like that of Chofapus; the tail is, of course, very different, but this is sufficiently accounted for 206 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. by the radically different manner of life. Scapula and pelvis are very similar in the two groups, and even the limb-bones, notwithstanding their very striking differences of proportions, have many features in common. Even the feet, unlike as they at first appear, are yet so fundamentally similar as to offer no difficulty to the assumption that the two groups were derived from the same ancestral stock. HAPALOPS RECTANGULARIS Ameghino. (Plate XL, Figs, i, i°.) Hapalops rectangularis Amegh. ; Enumeracion sistematica, etc., 1887, p. 22. Hapalops ellipticus Amegh.; Ibid. Schismotherium rectangularis Mercerat ; Rev. del. Mus. de La Plata, T. II. 1891, p. 9. Eucholceops ingens Lydekker, in part ; Anales del Mus. de La Plata, T. II, 1894, p. 99. The type of this species, and therefore of the genus, is a small frag- ment of the left mandibular ramus, in the La Plata Museum. Unfortu- nately, this fragment is very uncharacteristic and might belong to any one FIG. 29. FIG. 30. Type of Hapalops rectangularis, x \. Type of Hapalops ellipticus, x \. La Plata Museum. La Plata Museum. of several species. In the collection made by Mr. Brown for the Ameri- can Museum of Natural History is an excellently preserved mandible (No. 9222) with all of the teeth in place, which agrees very clearly with the corresponding portion of the type and is probably referable, to the same species. The first lower tooth is small, of compressed elliptical shape, with oblique abraded surface, which presents forward and outward ; -2, which fol- lows after a short diastema, is very broad and rectangular, with rounded angles ; ^ is similar, but more distinctly quadrate, while T is of the usual, subcylindrical shape. EDENTATA OF THE SANTA CRUZ BEDS. 2Oy The edentulous beak of the mandible is short and the chin rises quite steeply, with a concave profile ; the ascending ramus has a less sinuous ventral border than in H. longiceps, and the coronoid process, which is rather low and narrow, is more recurved, making a deeper sigmoid notch ; the angle is broad and heavy, but not very long, and has the ventral bor- der inflected, which makes the external side convex and the inner side concave. The postero-external opening of the dental canal is in the ascending ramus and presents so directly forward as to be nearly invisible in side view. MEASUREMENTS. Lower dentition, length 036 f width 0073 " " " j_f 025 Mandible, length from condyle 103 •j-, length (i. e., an tero-posterior diameter) .004 " " " angle 109 " width (i. e., transverse diameter) 005 " " of predental beak . . . .025 5-, length 0065 " depth below j : .024 " width 009 " thickness below 3- 013 3-, length 0065 " length condyle to y 045 " width 009 " height of coronoid 047 T, length 0075 " " " condyle 037 Associated with this mandible are a calcaneum and astragalus, so pecu- liar as to indicate the perfect distinctness of the species, provided, of course, that the association is not accidental. The astragalus has the nar- row and elongate shape common throughout the family, but the trochlea has quite a different shape from that of the other species ; its distal por- tion is relatively broader and the proximal part narrower, making the tibial border more oblique ; the inner condyle is shorter proximo-distally, more elevated and convex, and with a much more distinct tendency toward the assumption of the odontoid form than in any other known species of the genus, or, indeed, of the family. The calcaneum has the form com- mon to all the members of this genus, but is distinguished by the close approximation of the two astragalar facets, which are separated only by a very narrow sulcus, and by a slight reflection of the inner facet upon the dorsal side of the sustentaculum. MEASUREMENTS. Astragalus, length 030 Calcaneum, length 05 1 Astragalus, width of trochlea, proximal " proximal width of tuber. .. .044 end 016 " width of tuber at neck 015 Astragalus, width of trochlea, distal end .02 1 " " " distal end 023 " " neck . .016 2O8 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. HAPALOPS INDIFFERENS Ameghino. (Plate XXXIV, Figs. 1-5.) Hapalops indifferens Amegh. ; Enumeracion sistematica, etc., 1887, p. 22. Hapalops ( ? ) indifferens Mercerat; Rev. del Mus. de La Plata, T. II, 1891, p. 13. Rucholceops ingens Lydekker, in part ; Anales del Mus. de La Plata, T. Ill, 1894, p. 99. The type of this species, which is in the La Plata Museum, is an incom- plete right mandibular ramus, with the first tooth broken to the level of the jaw and the other teeth missing. To this species may be referred an indi- vidual in the Princeton collection (No. 15,110), which agrees very well with what is preserved of the type, save in regard to the position of the mental foramen, which in the latter is remarkably far forward, but this is FIG. 31. Type of Hapalops indifferens, x \. La Plata Museum. doubtless individual merely. The specimen consists of the anterior half of the skull, with mandible complete and all the teeth in place ; one cer- vical, ten thoracic, two lumbar and one caudal vertebrae ; the left ulna, lacking the distal epiphysis, and metacarpals II-IV of the left manus ; the left femur and a considerable portion of both hind-feet. In the upper jaw A is smaller than that of H. longiceps and of more oval section, and is implanted farther behind the maxillo-premaxillary suture ; the remaining upper teeth differ little, save in size from those of the last named species ; *• and A are usually more rectangular, while - has a more oblique position and has no vertical groove on the posterior face. In some individuals the outer side of a, a and A displays a vertical sulcus. Of the lower teeth T is small, erect, of oval cross-section and is separated by a short distance from ^ ; % and ^ are transverse and rectangular and i. is subcylindrical. EDENTATA OF THE SANTA CRUZ BEDS. 209 MEASUREMENTS. Upper dentition, length 050 &-, width 007 " " " -^6- 03 1 Lower dentition, length 041 1, length (z.^.antero-posterior diameter) .006 " " " ^ 027 " width (/. e., transverse diameter) 005 y, length 005 2-, length 006 " width 004 " width 008 5, length 007 &, length 007 " width oog " width 009 -g, length 007 A, length 007 " width 009 " width 0085 f, length 009 $-, length 005 5 " width 009 The skull varies considerably in its appearance and proportions ; in the more typical examples the skull is long and slender, with comparatively narrow muzzle and palate ; the postorbital constriction is shallower and more gradual than in H. longiceps, the forehead is narrower and the sagit- tal crest on the frontals is lower and thicker ; the nasals are shorter in the median line, but each has a very elongate lateral process which accom- panies the maxillary to the edge of the anterior nares. The preorbital fossa of the maxillary is quite shallow and the facial portion of that bone is continued to an unusual distance in front of - as a thin plate ; the dor- sal margin of this plate is strongly curved, making its vertical anterior edge very short dorso-ventrally. The premaxillaries, as is shown by a skull in the Ameghino collection, resemble those of H. longiceps in form, but are much less elongate, the difference being principally in the anterior branch, and the median notch in the palatine processes of the maxillaries for the spines of the premaxillae is larger and more regularly U-shaped. The mandible differs in only a few details from that of H. longiceps ; the predental beak is shorter and its dorsal border is much more nearly horizontal and is lower with reference to the level of the teeth ; the sym- physis is shorter and the profile of the chin rises more steeply, though compared with most other species of the genus, the beak is very long. The condyle is set upon a shorter neck than in H. longiceps and is thicker and more convex ; the coronoid process is lower, wider, more erect and less recurved, and the angular process is also shorter and wider and is less distinctly inflected. The postero-external opening of the dental canal is on the side of the ascending ramus. In the type-specimen the mental foramen has a much more anterior position than in the other mandibles referred to this species, but that is probably individual. 210 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. MEASUREMENTS. Skull, length from orbit to anterior nares .03 1 Palate, width at £ 012 " width at postorbital constriction . .033 Mandible, length from condyle 132 " " over lachrymals 054 " " " angle 134 Rostrum, width at base 026 " " of predental beak . . . .036 " " " anterior end 029 " " from condyle to T. .. .059 Palate, length in median line 054 " height of coronoid 059 " width at 1 026 " " " condyle 046 " " " preorbital fossae 024 " depth below ^ 027 " " " %• 014 " thickness below 3 016 Except for their smaller size, the vertebrae of the various regions are so like those of H. longiceps as to require no particular description. The ulna likewise differs but little from that of the last named species ; it is shorter and straighter and the shaft has a relatively greater transverse and smaller antero-posterior diameter, while the facet for the head of the radius is larger and more distinctly demarcated. The metacarpals differ from those of H. longiceps only in size. The femur, on the other hand, is quite different ; the head is set upon a less constricted neck and presents more obliquely upward, less inward ; the great trochanter is much lower, so that there is no notch between it and the head ; the process, though low, is very heavy and encloses a small, but deep digital fossa ; the second trochanter is much less prominent and more distal in position ; the shaft is notably narrower and less antero-pos- teriorly compressed ; the rotular groove is more concave and has more elevated borders, while the condyles display no noteworthy peculiarities. The pes is represented by the calcaneum, navicular, mesocuneiform, metatarsal IV and several phalanges. The calcaneum is quite strikingly different from that of H. longiceps; the tuber is narrower, thicker, less depressed planto-dorsally and more strongly arched, with more concave plantar face; the proximal end is much less expanded and its internal angle is much more thickened ; the process from the fibular side near the distal end is much less prominent and the two facets for the astragalus are farther apart. The other foot-bones require no description. MEASUREMENTS. Ulna, estimated length 176 Metacarpal II, distal width 012 " " of olecranon 030 Metacarpal III, length 036 " width at sigmoid notch 028 " " proximal width 019 Metacarpal II, length 035 " " distal width 015 " " proximal width 012 Metacarpal IV, length 044 EDENTATA OF THE SANTA CRUZ BEDS. 2 1 I Metacarpal IV, proximal width on Calcaneum, distal width 027 " " distal width . . '. OI2 " width at constriction 020 Femur, length from head 2OI Navicular, length on tibial side 013 " " " great trochanter ... .196 " " " fib ular side oio " proximal width 071 " width 024 " distal width over tuberosities . . . .062 Metatarsal IV, length 049 " " " " condyles 055 " " proximal width 014 " width of rotular groove 030 " " " thickness 023 Calcaneum, length 071 " " distal width 013 " proximal width 053 " " " thickness 019 The specimen upon which the foregoing description is founded was col- lected by Mr. Hatcher at Corriken Aike on the coast of Patagonia. HAPALOPS GRAND^VUS Mercerat. (Plate XLIII, Figs. 6, 6".) grandcevus Mercerat; Rev. del. Mus. de La Plata, T. II, 1891, P- 13- This species is very close to H. indifferens and may indeed be refera- ble to it, but the differences would appear to be quite constant. The fol- lowing description is drawn chiefly from a well-preserved mandible in the American Museum of Natural History (No. 9538) which agrees quite closely with Mercerat's type in the La Plata Museum. The first lower tooth, which in H. indifferens is of the usual subcylindrical form, in the present species is markedly trihedral, with the base of the triangle directed inward and slightly backward and the apex outward and slightly forward, two vertical sulci, one on the outer side near the posterior border and the other on the inner side near the anterior border, give the tooth a characteristically fluted or columnated appearance. The other teeth are like those of H. indifferens; ? and ^are transverse and rectangular, though a little broader on the internal and on the exter- nal side, and T is irregularly cylindrical and of curiously different shape on the two sides of the jaw. The mandible differs from that of H. indifferens in a number of respects, the most obvious of which is the somewhat shorter predentary beak, which has a more flared and depressed dorsal border. The condyle is set upon a shorter neck, narrowing the notch between condyle and angle ; the pos- terior border of the coronoid process is more curved, and the postero- 212 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. external opening of the dental canal is smaller and has a more inferior position at the base of the ascending ramus. MEASUREMENTS. Lower dentition, length 042 ^ , length 008 " " " -S? 0255 "width 008 j, length (i. t., antero-posterior diameter) .0055 Mandible, length from condyle 125 " width (i. e., transverse diameter) 005 j, length 007 " width 009 y, length 0075 " width 009 " of predentary beak . . . .032 " condyle to ^ 055 " depth at ^ 029 " thickness at -y 016 height of condyle 040 HAPALOPS ROBUSTUS Ameghino. Hapalops robustus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 316. Typical examples of this species seem very distinct, but the grada- tions are such that the propriety of separating it from H. indifferens is doubtful. It is not represented by well preserved specimens in the New York or the Princeton collection and I shall therefore quote Ameghino's diagnoses of it. " Size a little greater than H. indifferens, but more robust ; distinguished by the very broad palate, a little narrower in the middle than before or behind ; - small and cylindrical, T subelliptical, with postero-external side very broad and antero-external very narrow. Length of upper dental series 53 mm., of lower 38 mm. ; breadth of palate at -, 16 mm. ; at -, 22 mm." ('91', 316). "Size a little smaller than H. indifferens (it was erroneously stated to be a little larger in my description). The mandibular symphysis is shal- low and very elongate ; the part which extends in front of the first tooth is 35 mm. long. Length of skull from hinder edge of occipital condyles to the anterior border of the maxillary 170 mm. The maxillaries are prolonged in front of the first tooth more than in the other species ( 1 2 mm. on the palate)" (94", 145). The distinguishing feature of the skull is its great breadth, especially in the facial region, and the depth of the preorbital fossae, which are shal- low and ill defined in H. indifferens. In both species the molariform teeth have similar rectangular shapes. EDENTATA OF THE SANTA CRUZ BEDS. 213 HAPALOPS AGUIRREI (Mercerat). Tapinotherium aguirrei Mercerat; Rev. del Mus. de La Plata, T. II, 1891, p. 17. Hyperlepttis sectus Amegh., in part; 6num. synopt. d. Mamm. Foss. de Patagonie, 1894, p. 152. Eucholceops ingens Lydekker, in part; Anales del Mus. de La Plata, T. Ill, 1894, PI. LIX, fig. 2. The type specimen, a skull without mandible, which is in the collection of the La Plata Museum, is unfortunately much injured by crushing, which greatly obscures some of the more important diagnostic features. The species is of the type of H. robustus, to which it may prove to be refer- able, but it displays some peculiarities and certain suggestive approxi- mations to Encholceops, so that, for the present at least, it is advisable to keep it distinct. The specimen has already been figured by Lydekker ('94, PI. LIX, fig. 2), under the name E. ingens. H. aguirrei is one of the largest species of the genus, but in pro- portion to the size of the skull the teeth are strikingly small. The first upper tooth has the usual laterally compressed, oval section and is set much externally to the line of the other teeth, almost as much as in Eucholceops, and is separated from - by a long diastema ; a, 3- and A are of transversely oval shape and quite compressed antero-posteriorly ; of these teeth A is the largest and - the smallest ; A is much the smallest of the entire molariform series and 1 • r .-.• r • iVPC 0. 15,011. .109 .113 .117 .112 .137 .038 .047 .136 •135 .136 .132 .IDS .IOI .105 .101 .032 .036 .032 •033 .038 •037 .038 .045 .049 .052 .047 .050 .026 .030 .029 .025 .048 .050 .044 .046 .048 .047 .045 .048 .020 "" JD22 .023 .021 .043 .048 .048 .046 .OI5 .OI9 .021 .Ol8 •O2O .022 .O2I .O2I 222 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. No. No. No. No. No. No. I. 2. 15,597- 15,545- 15>l6°- 1 Palate, width at 4 ........................ 013 .on .012 .012 .010 « " « & ........................ oio .on .012 .011 .010 Rostrum, width over 1 ................... .026 .030 .029 .030 No. No. No. Mandible, length from condyle ............ .107 ?.ios " " " angle .............. -114 -"3 " " of predentary beak ....... .026 .026 ? .026 depth at s .................... .025 .024 .027 " height of coronoid .............. ' .05 3 .051 Vertebral Column, Ribs and Sternum. — The vertebral column has the following formula : C.y ; Th. 21-22 ; L. 3-4 ; S. 5-6 ; Cd ± 20. The atlas is relatively longer, higher and narrower than in H. longiceps and the neural arch is separated from the posterior cotyles; the neural canal is higher and narrower than in the latter species and the transverse processes are smaller ; the internal branch of the vertebrarterial canal is an open groove. The axis has a well-defined ventral keel, the facets for the atlas rise higher upon the sides of the neural canal, but project less below the centrum than in H. longiceps ; the odontoid process is rela- tively long and slender ; the neural canal is high and narrow and the spine is a hatchet-like plate, much more extended antero-posteriorly in some individuals than in others. The third cervical has a short, broad, de- pressed centrum, with indistinct ventral keel ; the neural arch is broad, the canal relatively large and the spine is a low ridge ; the transverse process, which is perforated by a short canal, does not project far out- ward from the side of the centrum, but is much extended antero-poste- riorly ; the pleurapophysial element is divided into nearly equal anterior and posterior portions, of which the former is rather more slender and pointed. The fourth cervical resembles the third, but has a slightly longer and narrower centrum, smaller neural canal, and more distinct spine. In the fifth, the spine is still more distinct and the anterior division of the trans- verse process is considerably shortened. The sixth vertebra differs from the fifth chiefly in the character of the transverse process, which is clearly distinguished into diapophysial and pleurapophysial elements ; the latter .is a large, compressed plate, which projects far below the level of the cen- trum ; the neural arch is very narrow antero-posteriorly. The seventh EDENTATA OF THE SANTA CRUZ BEDS. 223 cervical has a broader centrum than the sixth, with long, imperforate transverse processes, which are slightly expanded at the distal end, ter- minating in a recurved hook ; the neural arch is very narrow and the spine, through far shorter and more slender than that of the first thoracic, is yet much larger than on any other cervical. As a whole, the neck is short and slender, narrowing posteriorly, but increasing in dorso-ventral thickness, owing to the successively longer spines. The first thoracic has a centrum which about equals in size that of the seventh cervical, and the prezygapophyses are of cervical type ; the neural canal is low and wide, the arch is very broad and the spine, though but moderately developed, is yet the largest in the anterior part of the thorax ; this spine is elongate, broad and quite thick, and is expanded at the tip, making the anterior and posterior borders concave, but with only a slight backward inclination. The transverse processes are long, straight and ex- panded at the ends, which bear deep concavities for the tubercles of the first pair of ribs. The second thoracic differs considerably from the first, having a smaller centrum, much shorter transverse processes, and a longer, more slender and more inclined neural spine ; the prezygapophyses are still quite widely separated by a deep notch. In the succeeding vertebrae the centra are reduced, their small size in this region being one of the most characteristic features of the vertebral column ; the neural spines become shorter, more slender and more steeply inclined ; the transverse processes shorter and small, club-like metapophyses begin to appear upon their bases. This type of vertebra continues to the eight thoracic, after which the centra begin to enlarge and increase regularly in size backward, those in the hinder part of the region being far larger than those in the forward part ; on the last nine vertebrae are the two foramina opening on the ven- tral side of the centra, though, for the most part, these foramina are quite small. The neural arches are very broad in both directions and the spines become broader, thicker and more erect, though the spines of all the trunk-vertebrae have a more or less decided backward inclination. The last four thoracic vertebrae are of quite a different type from those which precede them and are unlike the lumbars ; the neural spines are rather short, but broad antero-posteriorly, and have but a slight backward slope ; the transverse processes bear no distinct facets for the tubercles of 224 PATAGONIAN EXPEDITIONS.' PALAEONTOLOGY. the ribs, but on the last thoracic that for the head of the last rib is like a step cut in the base of the transverse process ; short anapophyses are given off from the hinder borders of the transverse processes. The postzy- gapophyses of the last three thoracics and the prezygapophyses of the last two have the semicylindrical form characteristic of the lumbar region ; the accessory postzygapophyses first appear on the nineteenth thoracic, as small, ventrally facing facets, overlapping the accessory prezygapophyses of the twentieth vertebra, which are carried upon small, shelf-like pro- jections from the base of the principal pair of prezygapophyses. The lumbar vertebrae have broad and depressed centra, with two large foramina opening upon the ventral side of each ; the neural spines are some- what longer than those of the posterior thoracic region, but rather narrower and more erect ; the transverse processes are broad, depressed and thin, but of no great length ; the metapophyses diminish in size posteriorly and on the second lumbar are smaller than those of the last three thoracics ; the zygapophyses and accessory articular processes are like those, already described, of the posterior thoracic region, and no additional ones appear upon the lumbars. The sacrum consists of five vertebrae, all of which are large, though decreasing in size posteriorly ; the centra are broad and much depressed and are slightly concave on the ventral side, with ventral foramina on the first, fourth and fifth ; the neural canal is wide and low ; the foramina for the passage of the sacral nerves are large, especially those between the second and third vertebrae. The first sacral has well developed prezyga- pophyses and the last bears much smaller postzygapophyses ; those of the other vertebrae are indicated by roughened tubercles, and the neural spines are fused into a continuous ridge. Even in quite young individuals no division of the transverse processes into dia- and pleurapophysial ele- ments is apparent ; the first and second sacrals have large processes for articulation with the ilia, and the third has smaller processes, which touch the ilia only by the anterior border, while those of the fourth do not reach the pelvis and those of the fifth are connected with the ischia. As no specimen with a complete tail has yet been found, the number of caudal vertebrae is uncertain, but as in the other species of the genus, was probably about twenty, and they are relatively less heavy than in the large species. The first caudal has a short, broad and thick centrum and very elongate transverse processes, which are narrow and of only moder- EDENTATA OF THE SANTA CRUZ BEDS. 225 ate thickness ; the neural canal is still quite large and the spine promi- nent and heavy. Passing backward, the successive centra gradually lose the broad, subcubical form and tend to assume a more cylindrical shape ; the neural canal diminishes in size, but is complete to the tenth or eleventh vertebra, and zygapophyses are present on the same number, the anterior pair always much exceeding the posterior in size ; the trans- verse processes grow shorter and relatively wider and are especially expanded at the distal ends, where many of them are more or less dis- tinctly bifid. Near the end of the tail the vertebrae are very small and the processes rudimentary. In the anterior and middle regions of the tail the chevron-bones are Y- shaped, as in Megatherium, but with relatively shorter haemal spines ; these spines are longest in the anterior region and diminish posteriorly in length, but retain or even increase their fore-and-after breadth. Proxi- mally, the chevrons bear two pairs of facets for the vertebral centra, of which the anterior pair is larger and persists longer, the posterior pair becoming mere roughened ridges. In the hindermost part of the tail the chevrons are canoe-shaped, very short proximo-distally, elongated antero- posteriorly and pointed at both ends, much as in the armadillos and glyptodonts. As a whole, the vertebral column displays an interesting combination of characters ; its nearest resemblance is to the type of the Pleistocene Gravi- grada, but with such differences as might be expected in a more ancient, more primitive and very much smaller and lighter animal, while the very elongate trunk is much like that of Cholczpus. The actual length of the presacral part of the vertebral column is almost the same as in Myrme- cophaga jitbata, but in proportion to the skull and limbs it is far longer, while the tail is much shorter. The ribs are incompletely known, but the parts of the thorax are suffi- ciently represented in the various individuals to give a good idea of the whole. The first rib is very short and has a long, straight and very slender neck and a large, saddle-shaped tubercle ; the shaft has its broad side directed forwards and expands distally, where it is fused with the sternal rib. Most of the succeeding ribs are relatively rather short and are strikingly rod-like and slender, forming a decided contrast to those of the larger species, such as H. longiceps ; in the hinder portion of the thorax the tubercles are sessile and obscurely indicated, but apparently 226 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. only the last rib lacks the tubercle entirely. Seen from the side, the longer ribs display a double curvature, somewhat as in Cholczpus, though in a less marked degree. The sternal ribs are thin and blade-like, antero-posteriorly compressed, and with principal diameter directed dorso-ventrally ; the distal end bears a facet for the body of the mesosternal segment, and a rounded, tubercle- like projection for the ventral process of the segment. The sternum is imperfectly known and it is not possible to determine the number of segments of which it is composed. The manubrium, which bears considerable resemblance to that of Cholczpiis, is of cruciform shape, with long, narrow anterior projection ; the body of the presternum is broad, deeply concave on the dorsal side, and with narrow, elongate and saddle-shaped facets for the first pair of ribs ; the posterior end is narrowed and has a smooth surface for the first segment of the mesosternum ; this surface presents obliquely upward and backward. The segments of the mesosternum resemble those of Mylodon, as is true of all the Santa Cruz Gravigrada in which this structure is known. Each segment consists of a flat, depressed plate, with slightly concave anterior and convex posterior faces, and at the angles are facets for the heads of the sternal ribs ; from the ventral side of the plate arises a very large, club-shaped process, with constricted neck, which carries four concave facets for the tubercles of the sternal ribs ; except for these facets, the surface of the process is every- where rugose. No specimen containing the xiphisternum has yet been found. The following measurements of the vertebrae are from No. 15,545, except those of the lumbar vertebrae, which are taken from No. 15,011. MEASUREMENTS. Neck, length 140 Thorax, length (following curve). ..... .416 Loins, length 099 Sacrum, length 115 Atlas, length 030 width 050 dorso-ventral height 0265 Ax s, length of centrum 025 width of anterior face 029 " " posterior face 013 " " neural spine 026 Third cervical, length of centrum " " width of anterior face . . . " " " " posterior face . . Fourth cervical, length of centrum " " width of anterior face . . " " " " posterior face. First thoracic, length of centrum " " width of anterior face . . . " " " " posterior face . . First thoracic, width over transverse pro- cesses ,018 .0125 .014 .017 .013 .014 .018 .014 .017 .050 EDENTATA OF THE SANTA CRUZ BEDS. 227 MEASUREMENTS. First thoracic, height of spine from cen- trum 038 First thoracic, width of spine at tip 017 Third thoracic, length of centrum 019 " " width over transverse processes 041 Third thoracic, height of neural spine. . .033 " " width of neural spine at tip oio Last thoracic, length of centrum 02 1 " " width of anterior face ... .022 " " width over transverse processes ,. 7.049 Last thoracic, height of neural spine . . . .040 " " width of neural spine. . . .018 First lumbar, length of centrum 025 " " width of anterior face 025 " " width over transverse pro- cesses 080 First lumbar, height of neural spine 044 " " width of spine at tip 020 Second lumbar, length of centrum 026 " " width of anterior face. .025 Third lumbar, length of centrum 023 width of anterior face 026 width over transverse processes 064 Third lumbar, height of neural spine. . . .047 Fourth lumbar, length of centrum 025 " " width of anterior face . . .026 " " height of neural spine ., .045 First sacral, width of anterior face 029 Last sacral, width of posterior face 026 First caudal, length of centrum 019 " " width of anterior face 023 " " width over transverse pro- cesses 076 Second caudal, length of centrum 018 " " width of anterior face . . .023 " " width over transverse processes 070 Third caudal, length of centrum 020 " " width of anterior face 021 " " width over transverse processes 060 Fourth caudal, length of centrum 021 " " width of anterior face .. .020 " " width over transverse processes 056 Fifth caudal, length of centrum 02 1 " " width of anterior face 019 " " width over transverse pro- cesses 055 Sixth caudal, length of centrum 020 " " width of anterior face 018 " " width over transverse pro- cesses. 052 Seventh caudal, length of centrum 019 " " width of anterior face .. .016 " " width over transverse processes 046 Appendicular Skeleton. — The scapula has a short, broad blade, divided by the spine into fossae of nearly equal width ; the suprascapular border is quite short and anteriorly curves gradually into the coracoid border, while behind it forms a decided angle with the glenoid border; the latter is much thickened on the neck of the scapula and, though thinning away proximally, remains a distinct ridge for most of its length. The neck of the scapula, even excluding the coracoid, is very broad and short. The spine is of moderate height and pursues a somewhat curved course, end- ing in a very large acromion, which unites with the coracoid, as in all known Gravigrada. The coracoid is very large, forming the anterior third 228 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. of the glenoid cavity and, proximal to this cavity, expanding into a broad plate, which is suturally connected with the blade of the scapula and eventually fuses with it, while a shorter and more rod-like process coal- esces with the acromion. The coracoscapular foramen is quite small and of subcircular shape. The clavicle is rather slender and is more curved than in Mega /onyx, less than in Megatherium or Mylodon ; this curvature is single and pre- sents the convexity forward ; the sternal end is moderately expanded. The humerus (Plate XLI, fig. 4) is very like that of H. longiceps, but much smaller and lighter ; the proximal end is shaped much as in Mega- lonyx, though the tuberosities are more widely and distinctly separated and their proportions are reversed, the inner one exceeding the outer in size ; the bicipital groove is broad and shallow ; the deltoid area is rela- tively somewhat narrower than in H. longiceps and has less elevated borders. The distal trochlea is proportionately narrower than in the latter species and the radial part of the trochlea is relatively larger and more hemispherical, while the ulnar facet is narrower and has a less prominent inner flange. Otherwise, the distal end is almost exactly as in H. longiceps. Except for their smaller size and somewhat more slender proportions, the ulna and radius are so like those of the larger species as to require no extended description. Very little of the manus is preserved in association with any of the specimens and the few parts that are known differ only in size from the corresponding parts of H. longiceps. MEASUREMENTS. No. No. No. No. 15,545- 15,160. 15,597- I5,i55- Scapula, length of blade .101 " greatest width of blade .082 " width of glenoid cavity .019 Humerus, length 151 .152 " width of proximal end 040 .040 " " " distal trochlea 028 .030 " " " " end over epicondyles ... .060 Radius, width of proximal end 019 .018 " " distal end '. .023 .021 Ulna, length . 1 56 " " of olecranon 025 .026 .025 EDENTATA OF THE SANTA CRUZ BEDS. 22Q No. No. No. No. 15,545- 15,160. 15,597. 15,155- Ulna, width at sigmoid notch 022 .020 .020 Metacarpal II, length -0295 " " width of proximal end .017 " " " " distal end .0115 " " thickness of distal end .016 Save in size, the pelvis differs little from that of H. longiceps. The ilium is quite long and broad and runs nearly parallel with the sacrum, though somewhat everted at the anterior end ; the acetabular border is external, making the broad gluteal surface dorsal, as in all this group. The ischium is much shorter than the ilium and the sacro-sciatic foramen is a longi- tudinal oval. The pubis is a slender, compressed rod and the symphysis is short; the obturator foramen is triangular, with principal diameter parallel with the pubis. The femur (Plate XLI, fig. 5) is relatively longer and more slender than in H. longiceps, though there is little difference in appearance ; the head is small and hemispherical and on its postero-internal side, hardly visible from the front, is the pit for the round ligament, a large, irregular depression, which does not extend to the margin of the articular surface ; the great trochanter is less prominent than in H. longiceps and the notch between this process and the head is shallower; the second trochanter is extended well down upon the inner side of the shaft, while the third tro- chanter has a little more proximal position than in the larger species. The shaft is less antero-posteriorly compressed than in the latter and its surfaces are more convex. The distal tuberosities are less developed. The patella is long, narrow and thin ; its distal prolongation is much narrower than in H. iongiceps, remarkably so in some individuals. The tibia and fibula (Plate XLI, fig. 6) differ little, except in size, from those of H. longiceps, but much individual variation, due partly to differ- ences of age, is observable ; the only feature calling for notice is the flatness of the astragalar facet of the tibia. The pes (Plate XLI, figs. 1-3, 7) is of a type entirely similar to that of H. longiceps, differing only in a few details, but the variations in the form of the calcaneum and astragalus are remarkable, no two specimens of these bones being in all respects alike. The astragalus has the narrow, elongate shape seen in all the species of the present genus, but the tro- chlea is much less distinctly grooved than in H. longiceps and is less 230 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. deeply invaded by the notch from the distal end, while the facet for the navicular is somewhat less deeply concave. The calcaneum has much the same general shape as in H. longiceps, but the tuber is thinner planto- dorsally and is less expanded and rugose at the free, or proximal end ; this difference is especially marked in the younger and smaller individuals ; the position of the two facets for the astragalus and of the cuboid facet differs more or less in every specimen, though they are essentially similar to the corresponding surfaces on the calcaneum of H. longiceps. The remaining bones of the tarsus display no peculiarities that require notice. The metatarsals resemble those of the larger species, with the quite constant exception that metatarsals IV and V are shorter in proportion to the length of metatarsal III, and that the latter, though extremely short and heavy, is yet rather less massive. The phalanges differ only in size from those of H. longiceps. MEASUREMENTS. No. No. No. No. No. 15,011. 15,545- 15,160. 15,507. 15,155- Pelvis, length 1 97 .200 " greatest width 225 .235 Ilium, length 114 .115 " greatest width 075 .077 Ischium, length 083 .085 Acetabulum, antero-posterior diameter 034 .032 Femur, length from head .172 " " " great trochanter .175 " width of proximal end .063 " " " distal end over tuberosities . . .054 " " " " condyles .048 " " " rotular trochlea .024 Patella, length .032 .038 " greatest width .025 .022 Tibia, length . 1 24 " width of proximal end -049 .05 1 " thickness of proximal end -039 .040 .041 " width of shaft in middle .018 -0175 " thickness of shaft in middle .015 .015 " width of distal end .043 " thickness of distal end .021 .021 Fibula, length .121 " width of proximal end .013 " thickness of proximal end .020 EDENTATA OF THE SANTA CRUZ BEDS. 231 No. No. No. No. No. 15,011. 15,54.5. 15,160. 15,597. 15,155. 15,545 Fibula, width of shaft in middle .008 " thickness of shaft in middle .010 width of distal end .02 1 " thickness of distal end .018 Calcaneum, length " width of proximal end " " at constriction " " of distal end .023 Astragalus, length .03 1 " width of trochlea .021 " " distal end .016 Metatarsal I, length .013 " " proximal width .007 " " distal width .007 " " " thickness .009 Metatarsal II, length 022 .024 " proximal width 012 .013 " distal width oio .01 1 " " thickness .016 .017 Metatarsal III, length 020 .024 .022 " proximal width 016 .017 .017 Metatarsal III, distal width 015 .015 .015 " " thickness 020 .022 .020 Metatarsal IV, length 035 .040 " proximal width 013 .012 " distal width oio .01 1 " thickness 016 .018 Metatarsal V, length 029 " proximal width 025 " " distal width 007 " " " thickness 009 First phalanx, digit II, length " " proximal width " " " thickness First phalanx, digit III, length " " proximal width " " " thickness Second phalanx, digit II, length " " proximal width " " " " " thickness.. . . Ungual, digit II, length " " proximal thickness Ungual, digit III, length " " proximal thickness .057 .047 .015 .023 .032 .0225 .016 .024 .013 .on .016 .023 .017 .015 .021 .041 .013 .Oil .017 •035 .026 .009 .OIO .on .012 .017 .013 .013 .020 .020 .0095 .017 .036 .0155 .047 02 1 232 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. HAPALOPS ANGUSTIPALATUS Ameghino. (Plate XLIII, Figs. 2-5.) Hapalops angustipalatus Amegh. ; Rev. Argent. Hist. Nat, Vol. I, 1891, p. 316. This is another species of doubtful validity, for it may very well prove to be identical with some of the species which have been established upon the mandible alone. The type specimen is the facial portion of a skull, with all of the teeth, except -, in position. In the Princeton collection the species appears to be represented by a specimen (No. 15,562), com- prising a considerable part of the skeleton, which was collected by Mr. Hatcher at Corriken Aike. This individual consists of the skull, of which only the base is preserved, without mandible, seven thoracic and four lumbar vertebrae, parts of the scapula and humerus, the radius, ulna, meta- carpals II and III, femur, patella, tibia and part of the pes. H. angustipalatus is distinctly larger than H. elongatus; individuals of the latter yield measurements which form a series of gradations from the smaller to the larger specimens, while the dimensions of H. angustipalatus are separated by a wide gap from those of the largest representatives of H. elongatus. Another difference from the latter is in the relative size and proportions of the skull, which is considerably smaller in comparison with the vertebrae and limb-bones, and broader in proportion to its length than in the last named species. The teeth are not especially characteristic; the caniniforms (A) are relatively large, sharply pointed by abrasion and are placed somewhat more externally to the line of the other teeth than is usual in this genus. The molariform teeth are large and of more or less distinctly rectangular outline, except &, which is very small and transversely oval. The skull is relatively broader than in most examples of H. elongatus and the occipital condyles and foramen magnum are larger, while the basioccipital and basisphenoid are broad and quite flat transversely. The descending processes of the alisphenoids and the pterygoids, which form the side-walls of the posterior nares, are less produced downward than in H. elongatus. The hard palate is more decidedly convex between the molariform teeth than in the latter species and wider between the canini- forms, while the anterior median notch for the premaxillary spines is distinctly smaller. On the other hand, the preorbital fossae of the maxil- EDENTATA OF THE SANTA CRUZ BEDS. 233 laries are deeper, producing a stronger constriction of the palate at the diastema. MEASUREMENTS. Upper dentition, length 046 Skull, length occipital condyles to an- " " " £"•&• 030 tenor nares 145 " " " 1~A 0385 Cranium, length to edge of orbit 1 16 1, length (i. e., antero-posterior diame- Face, length orbit to anterior nares.. . .033 ter) 006 Occiput, width at base 057 " width (i. e., transverse diameter). . . .005 Skull, width over lachrymals 055 ^, length 006 Zygomatic arch, length 083 " width 008 Occipital condyle to glenoid cavity, £, length 007 length 023 " width 009 Occipital condyle to •&, length 071 A, length 006 Palate, length in median line 045 " width 0085 " width at i 020 £, length 0105 " " " preorbital fossae 023 " width 007 " " " ^ 013 Skull, length in median line 122 " " " - 0115 Rostrum, width over 1 034 The thoracic vertebrae, especially those from the posterior part of the region, are considerably larger than the corresponding ones of H. elongatus, more so than would be expected from a comparison of the skulls alone ; they have higher, broader, thicker and more erect spines. Only on the last thoracic are the small ventral foramina visible. The lumbar vertebrae (Plate XLIII, fig. 5, 5" 5*) form a series of four, which in this specimen are in an unusually complete state of preservation. The centra are broad and depressed, increasingly so toward the sacrum, and, although this animal is fully adult, the ventral openings of the canals which traverse the centra are very conspicuous, especially on the second vertebra, becoming quite small on the last. The neural spines are higher, broader, more thickened at the free end and less inclined backward than in H. elongatus ; the transverse processes are quite short, broad and de- pressed, and are curved forward, they are longest on the second lumbar. The accessory articular processes, which are particularly well shown in this individual, are of the type already described as characteristic of the Megalonychidce. Two pairs of such processes are developed, an anterior pair placed upon a shelf-like projection of the neural arch, ventral and external to the prezygapophyses, and a posterior pair which arise from the hinder angulation of the transverse processes. 234 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. The ribs, so far as they are preserved, are similar to those of H. elon- gatus but are relatively somewhat broader and stouter. The two segments of the mesosternum (Plate XLIII, figs. 3, 3", 4, 4°) most resemble the second and fifth segments of Mylodon (Owen, '42, PI. IX) to which they closely conform in plan of structure ; the dorsal portion of the more anterior segment is an elongate and narrow plate, broadening and becoming more depressed posteriorly; the ventral portion is corres- pondingly elongate antero-posteriorly. The eight facets for the sternal ribs are as in all the other Santa Cruz Gravigrada in which the sternum is known. The more posterior segment is much broader and the ventral part is much less extended in the fore-and-aft direction. MEASUREMENTS. Last thoraqic, length of centrum 025 " " width of anterior face ... .027 " " " over transverse pro- cesses 056 height of neural spine . . . .036 " " width of neural spine at base 023 " " width of neural spine at tip 022 First lumbar, length of centrum 027 " " width of anterior face 030 " " height of neural spine . . . .038 " " width of spine at base ... .023 " " " " " "tip 023 Second lumbar, length of centrum 028 Second lumbar, width of anterior face. . .030 " " " over transverse processes ?. 100 " " height of neural spine .. .041 Third lumbar, length of centrum 027 " " width of anterior face ... .031 " " " over transverse pro- cesses 092 " " height of neural spine ... .036 Fourth lumbar, length of centrum 025 " width of anterior face. . .033 " " " " posterior face. .037 " height of neural spine .. .031 " " width of spine at tip. . . .023 The bones of the fore-limb closely resemble those of H. elongatus but are somewhat longer and decidedly heavier. The scapula differs in a number of particulars, having a more sinuous coracoid border and broader prescapular fossa ; the glenoid cavity is more deeply concave and the spine bears a more distinct metacromion. Of the humerus, somewhat less than the distal half is preserved; in the trochlea the articular surface is continuous, as is usual throughout the order, and yet the groove between the radial and ulnar facets is con- siderably deeper than in H. elongatus and the latter has a shorter prox- imo-distal diameter, being reflected less upon the dorsal face of the bone ; i EDENTATA OF THE SANTA CRUZ BEDS. 235 the internal epicondyle and the supinator ridge are very heavy and promi- nent, but the supratrochlear and anconeal fossae are even shallower than in the last named species. The ulna is but little longer than that of H. elongatus and considerably stouter; the olecranon is somewhat broader at the free end and the humeral facet is of a rather different shape, being wider and also extend- ing farther up on the external side. The shaft is quite heavy and the strongly convex curvature of the posterior border gives it quite a dif- ferent appearance from that of the preceding species. The radius differs very little, except in being heavier, from that of H. elongatus; the broadening of the shaft below the proximal half is some- what greater and more abrupt and on the anterior side of the distal end is a broad and deep sulcus for the extensor tendons ; the carpal facet is unusually concave. MEASUREMENTS. . Scapula, width 089 Radius, length 137 " antero-posterior diameter of " width of proximal end 020 glenoid cavity 029 " " " distal end 026 Scapula, width of glenoid cavity 022 Metacarpal III, length 033 Humerus, width of distal trochlea 034 " " proximal width °I95 " " " " end over epi- " " distal width 013 condyles 065 " " " thickness 0185 Ulna, length 161 Metacarpal IV, length 038 " " of olecranon .027 " " proximal width oio " width at sigmoid notch 024 " " distal width 012 " of distal end 013 " " " thickness .015 The femur differs considerably from that of H. elongatus; the head is larger and rises considerably above the level of the great trochanter, and the pit for the round ligament is extended to the edge of the articular sur- face ; the great trochanter is lower and there is no notch between this process and the head ; the shaft is considerably broader and more com- pressed antero-posteriorly, while the third trochanter and external tuber- osity are more prominent ; the rotular groove is shallower. The tibia differs from that of the preceding species only in its length and greater relative stoutness, and the same description applies to the calcaneum and metatarsals III and IV. Compared with H. e/oiigafns, the hind limb exceeds the fore limb more in length. 236 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. MEASUREMENTS. Femur, length from head 190 Tibia, thickness of distal end 023 " " " great trochanter . .187 Calcaneum, length 065 " width of proximal end 071 width of proximal end 053 « <• " distal end over tuber- " " at constriction 020 osities 065 " " of distal end 025 " " distal end overcondyles .054 Metatarsal III, length 027 Patella, length 039 " " proximal width 019 " greatest width 029 " " distal width 017 Tibia, length 140 " " distal thickness 0235 " width of proximal end 055 Metatarsal V, length 035 " thickness of proximal end 043 " " proximal width 033 " width of shaft in middle 020 " " " thickness 015 " thickness of shaft in middle 019 " " distal width oio width of distal end 046 " " thickness 012 ? HAPALOPS PONDEROSUS, sp. nov. (Plate LIV, Figs. 2, 2°.) A large species which may perhaps be referable to Hyperleptiis rather than to Hapalops, but the median notch of the palate which receives the premaxillary spines would seem to indicate that the premaxillae had the shape chararteristic of the present genus. The type specimen (Princeton Museum, No. 15,520) consists of the skull, without mandible, humerus, femur, proximal half of the tibia, and the calcaneum ; it was collected by Mr. Hatcher, probably at Corriken Aike. The first upper tooth is small, of longitudinally oval section and abraded almost horizontally. The molariform teeth are unusually large and rect- angular, not quite like those of any other specimen ; - is of almost square section ; - is a transverse rectangle and the largest of the series ; - is simi- lar, but a little smaller, while - is much reduced in size. The two series of molariform teeth are almost exactly parallel, making the palate of uni- form width between them. MEASUREMENTS. Upper dentition, length 062 ^, length 009 " " " 4-6- 041 " width 0115 J-, length (i. e., antero-posterior diameter). .007 A, length 008 " width (i. e., transverse diameter) 006 " width 01 1 i, length 008 £, length 006 " width oio " width 009 EDENTATA OF THE SANTA CRUZ BEDS. 237 The skull also is of a somewhat peculiar type. The occiput is quite high and slopes forward and upward more than in most species of Hapa- lops. From the occipital crest the upper contour of the skull rises slightly to the parietal eminence, which is quite low, and thence descends very gradually to the muzzle, so that the dorso-ventral diameter of the skull is nearly uniform throughout. The brain-case is broad and capacious, the postorbital constriction shallow and the expansion forward from it unusu- ally gradual ; the sagittal crest is not developed, save for a short distance upon the frontals, which on the sides are uncommonly concave to form the wall of the orbits ; the preorbital fossae are of moderate depth. The occiput is broadly convex, with a median ridge for the vermis of the cerebellum and a shallow fossa on each side ; the condyles are quite large, projecting well below the level of the basioccipital and are widely separated by the large foramen magnum. The occipital crest is quite prominent on the sides, becoming inconspicuous dorsally, where the supraoccipital is reflected for a short distance upon the cranial roof. The hard palate is moderately convex between the molariform teeth, flattening anteriorly ; its rugosities receive a somewhat characteristic appearance from their being arranged in three or four longitudinal rows, or ridges ; the median notch for the premaxillary spines is broad and U-shaped. MEASUREMENTS. Skull, length in median basal line 148 Skull, width over lachrymals 056 " condyle to anterior nares. .174 Zygomatic arch, length 100 Cranium, length from condyle to rim of Distance from condyle to glenoid cavity. .027 orbit 135 " " " " i 087 Face, length from rim of orbit to anterior Palate, length in median line 060 nares 043 " width at i 026 Occiput, height 046 " " " preorbital fossae 029 " width at base 065 " " <•' & 018 Skull, width at postorbital constriction. .036 " " " & 019 The humerus differs but little from that of//, longiceps ; the shaft is somewhat more slender, the deltoid area narrower, with less rugose and prominent edges; the distal trochlea is rather wider and has a more hemispherical facet for the radius, while the anconeal fossa is distinctly deeper; the internal epicondyle is quite as massive and prominent, but the bony bridge over the foramen is considerably narrower. 238 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. The femur also is very like that of H. longiceps in size and proportions ; the head is somewhat larger and the pit for the round ligament is of more pyriform shape, its apex extending to the hinder margin of the articular surface. The great trochanter is relatively higher, making deeper the notch between itself and the head ; the digital fossa is larger and deeper, more so than in any other specimen in the collection ; the third trochanter has about the same relative position as in H. longiceps, but projects more prominently and is narrower proximo-distally. The shaft is broader, especially its proximal portion. The rotular groove is broad and shallow, with raised internal border, while the tuberosities are unusually large and rugose. In the tibia, so far as it is preserved, the only noteworthy difference from that of H. longiceps is the greater slenderness of the shaft. The calcaneum resembles that of the last named species ; the proximal end of the tuber is more expanded and less oblique, making the lateral borders more concave; the external astragalar facet is larger, and the projection from the outer side of the distal end more prominent. MEASUREMENTS. Humerus, length 1 94 Femur, width of distal end over tuber- " width of distal end over epi- osities 078 condyles 075 " " " rotular groove 032 " " " " trochlea 041 Tibia, width of proximal end 072 Femur, length from head 216 " thickness of proximal end 051 " " " great trochanter . . .219 Calcaneum, length 076 " width of proximal end 090 " width of proximal end 066 " " " shaft above second tro- " " at constriction 023 chanter 070 " " of distal end 032 " " " distal end over condyles .069 HAPALOPS INFERNALIS Ameghino. Eucholceops infernalis Amegh. ; Enumeracion sistem., etc., 1887, p. 21. Pseudhapalops infernalis Lydekker; Anales del Museo de La Plata, T. Ill, 1894, p. 103. As Lydekker has pointed out (loc. cit), this species is not referable to Eucholceops. Unfortunately, the type specimen, the anterior part of a skull, is in a much damaged condition, but apparently indicates a species dif- ferent from any of the preceding representatives of Hapalops. The upper EDENTATA OF THE SANTA CRUZ BEDS. 239 caniniform (A) is of medium size and of the usual compressed oval section ; it is inserted somewhat behind the anterior border of the maxillary and is separated by quite a long diastema from i. The two series of molariform teeth are almost exactly parallel, making the palate of uniform width in this region. These teeth (A~i) are characterized by their relatively large antero-posterior diameter; in shape they are rectangular with rounded angles ; A is the largest and A the smallest of the series. The preorbital fossae of the maxillaries are unusually deep. MEASUREMENTS. Upper dentition, length 060 £, width OIO *•-&• 035 A, length 006 Diastema, length 017 " width 009 1, length (/'. e., antero-posterior diameter) .008 £, length 0055 " width (i. e., transverse diameter) 006 " width 008 £, length 006 Palate, width at preorbital fossae 030 " width 008 " " "3. 016 S-, length 008 " " "4 016 HAPALOPS ROSTRATUS Ameghino. (Plate XLIII, Figs, i, i«.) Xyophorus rostratus Amegh. Enumeracion sistem., etc., 1887, p. 23. f Xyophorus simus Amegh., Ibid., p. 23. Although the type of this species is an unsatisfactory fragment of the mandible belonging to a very young animal, the name may be employed for those small representatives of Hapalops, with very short predentary beak of the mandible, which Ameghino has placed in a distinct genus, Xyophorus. The following description is taken from a specimen in the Princeton collection, which consists of an imperfect skull, with mandible, one lumbar, five sacral and four caudal vertebrae, the right os innominatum, part of the right radius and femur and two phalanges of the pes. So far as the teeth are concerned, this species hardly differs at all from H. elongatus ; - is of slightly compressed, longitudinally oval cross-section, and is obliquely bevelled by abrasion ; - is quite small and of subquadrate form ; a has a transversely rectangular shape, while - has some tendency to assume a transversely oval shape. In the mandible, T is of quite dif- ferent size and form on the two sides, being noticeably lower and broader on the right side than on the left ; the diastema is very short. The only other tooth preserved is ^, which is of the usual form. 240 PATAGONIAN EXPEDITIONS '. PAL/EONTOLOGY. MEASUREMENTS. Length of diastema between A and ? . . .014 A, width 0075 1, length (/'. e., antero-posterior diam- Lower dentition, length 033 eter) 0055 " " " ^_¥ 022 5 " width (/. e., transverse diameter). .. .005 Diastema between T and j, length 0065 i, length 006 T, length 0045 " width 0065 " width. 004 i, length 006 j, length 006 " width 0075 " width 008 A length 005 What little remains of the skull differs hardly at all from that of H. elongatus except in size ; the rostrum is a little shorter and wider and the preorbital fossae rather deeper than in most individuals of the latter, but it is extremely probable that the premaxillae were decidedly shorter. The jugal has the same general shape as in H. elongatus, with the usual broad, descending, suborbital plate ; the posterior process is, however, quite different, being broader and more compressed, much less slender and rod- like; while the notch for the insertion of the zygomatic process of the squamosal is much better defined. The mandible is shorter and wider than in H. elongatus and has quite a different type of predentary beak ; this beak is shorter, broader behind, narrowing forward much more rapidly, and ending in a point instead of a rounded border ; the edentu- lous margins are much more everted or flared and the symphysis is less deeply excavated on the dorsal side. In side-view, the short beak gives to the mandible quite a different appearance. The postero-external open- ing of the dental canal occupies the same relative position as in H. elongatus. MEASUREMENTS. Zygomatic arch, length 060 Mandible, width of predental beak in Skull, width over lachrymals 045 " front of T 021 Rostrum, width at base 028 " depth of ramus below 3- 022 " over 1 029 " thickness of ramus below 3-. .013 Mandible, length of predental beak .. . .0225 The type of Xyophorus simus is a similar, uncharacteristic fragment of the mandible, which, though considerably larger than that of X. rostratus, may very well belong to an old individual of the same species. EDENTATA OF THE SANTA CRUZ BEDS. 241 HAPALOPS ATLANTICUS Ameghino Xyophorus atlantictis Amegh. ; Rev. Argent, de Hist. Nat.T. I, 1891, p. 320. Xyophorus andinus Amegh.; Ibid., p. 321. This species, which is as yet known only from three mandibles in the Ameghino collection, differs from the preceding one principally in size, being much larger and more robust. The lower teeth are similar in char- acter to those of H. rostratus, but the series varies in length from 38 to 43 mm.; the horizontal ramus is deeper dorso-ventrally and the preden- tary beak equally short, so that the profile of the chin rises somewhat more steeply forward. The border of the ascending ramus is more inclined backward and the postero-external opening of the dental canal is distinctly lower in position. In the largest of the three individuals the depth of the horizontal ramus below -5 is 30 mm. HAPALOPS RECTANGULIDENS Ameghino. Parhapalops rectangulidens Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 310. Parhapalops rectangiilaris Amegh.; Enum. Synopt. de Mamm. Foss. de Patagonie, 1894, p. 146. Eleutherodon heteroclitus Mercerat ; Rev. del Mus. de La Plata, T. II, 1891, p. 24. ? Parhapalops pygmcetts Amegh. ; Enum. Synopt. de Mamm. Foss. de Patagonie, 1894, p. 146. In almost all of the species of Hapalops the last lower molar is of more or less distinctly cylindrical form ; in the present species, however, this tooth is antero-posteriorly compressed and its principal diameter is trans- verse. In addition to the type in the Ameghino collection, there is in the La Plata Museum a mandible (type of Eleutherodon heteroclitus Mercerat) which agrees well with the type-specimen in size and in the peculiar form of T, though differing very markedly in the shape of ^ and 7. The analogy of other species would indicate that the agreement in the shape of T is of greater taxonomic significance than the difference of -% and ^. Hence, the two species should be at least provisionally united. The first tooth (T) has the usual oval cross-section and is separated from ^ by a short diastema. In the type ^ is subquadrate, while in the La Plata specimen this tooth is more antero-posteriorly compressed and trans- 242 PATAGONIAN EXPEDITIONS! PAL/EONTOLOGY. versely oval. In both individuals 7 resembles -%, while T is transversely extended and not subcylindrical. The mandible itself displays no important peculiarities ; the predental beak most resembles that of H. rostratus, being short, broad at the base and tapering rapidly forward, with strongly everted or flared dorsal borders. MEASUREMENTS. Type. La Plata Specimen. Lower dentition, length 034 -O295 " " " v-ii 023 -Ol85 T, length (/. e., antero-posterior diameter) 0055 .005 " width (i. e., transverse diameter) 0045 -0035 y, length 007 .005 " width 009 .008 j, length 007 .005 " width 0085 .009 f, length 007 .006 " width 0085 .008 HAPALOPS CONGERMANUS Ameghino. Amphihapalops congermanus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 319. Amphihapalops gallaicus Amegh. ; Ibid., p. 319. Amphihapalops cadens Amegh. ; Ibid., p. 320. This very imperfectly known species is of doubtful validity ; it is of medium size and is distinguished by the elevated position of the postero- external opening of the dental canal, which is placed higher upon the ascending ramus than in any of the preceding forms. The three species which Ameghino has named do not differ from one another more than would be expected from the very different ages of the type-specimens. Ameghino has proposed a genus, Pseudliapalops, which is characterized by the position of the postero-external opening of the dental canal ; this foramen opens laterally, instead of anteriorly, and is situated upon the horizontal rather than the ascending ramus. Although this is a fairly con- stant character, with comparatively few intergradations, it does not seem to be of sufficient importance to require a generic distinction. The astraga- lus found with the type-specimen of P. observation is was evidently in only EDENTATA OF THE SANTA CRUZ BEDS. 243 accidental association and is referable to some much smaller species, per- haps of a different genus. HAPALOPS RUETIMEYERI Ameghino. (Plates XXXVII, Figs. 4, 6 ; XXXVIII, Figs. 4, 6 ; XXXIX, Figs. 4, 4°, 6, 6" ; XLII, Figs. 4-8.) Hapalops ruthmeyeri [sic] Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 153. Pseudhapalops rtdimeyeri Amegh.; fenum. Synopt. d. Mamm. Foss. de Patagonie, 1894, p. 151. Pseiidhapalops ruetimeyeri Lydekker ; Anales del Museo de La Plata, T. Ill, 1894, p. 101. Pseudhapalops observations Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 319, Geronops circularis Amegh.; Ibid., p. 320. Eugeronops circularis Amegh.; Ibid., p. 397. Pseudhapalops circularis Amegh., Sec. Censo de la Repub. Argent., T. I, 1898, p. 199. This is a small species, considerably smaller than H. elongatus and dif- fering from the latter not only in the position of the external dental fora- men of the mandible, but also in several details of structure of the skull and skeleton. A finely preserved specimen, collected by Mr. Brown for the American Museum of Natural History (No. 9,250), consisting of the greater part of a skeleton, agrees so well with the type, that it may be re- ferred to the same species, though the unfortunate absence of the man- dible prevents the reference from being quite certain. As is almost in- variably the case among the Santa Cruz Gravigrada, there are many individual differences between the two specimens, increased, no doubt, by their difference in age ; in spite of its slightly larger size, the type is a very young animal, with widely open palatal suture, while the New York specimen is thoroughly adult. A third skull, likewise in the collec- tion of the American Museum (No. 9,293) may be provisionally referred to the same species, though it differs in some significant respects from both of the others, and in this case also the absence of the mandible makes the reference uncertain. The first upper tooth (-) is quite small and is placed a little farther behind the anterior edge of the palate than in H. elongatus. In two of 244 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. the specimens this tooth has the usual bevelled crown, but in the third (No. 9,293) we find a very interesting difference, at least on the right side, the crown of the left side being broken ; in the specimen in question the tooth is not bevelled and caniniform, but transversely grooved, like the molariform teeth. This is the only known instance of the kind among the Santa Cruz Gravigrada and is doubtless an individual abnormality, but it is of interest as showing how readily the caniniform may be changed into a molariform tooth, as has occurred, for example, in Megatherium. The diastema is of varying length, though always quite short, and the molari- form teeth are transversely rectangular ; - is quite small, - and - con- siderably larger, and & very small. MEASUREMENTS. Type. No. 9,293. No. 9,250. Upper dentition, length 043 .041 .040 " " 1-i 029 .027 .027 1, length (i. e., antero-posterior diameter) 005 .005 .005 " width (i. e., transverse diameter) °O35 -003 .004 1, length 005 .005 .005 $ " width 006 .007 .007 •3-, length 006 .006 .0063 " width 008 .0085 .008 ±, length 006 .006 .006 " width 0075 .008 -0075 i, length 003 .004 .0035 " width 007 .006 .0065 The skull (Plates XXXVII, figs. 4, 6; XXXVIII, 4, 6; XXXIX, 4, 4", 6, 6a.) has much the same general appearance as that of//, elongatus, but besides being smaller, differs in a number of details. The occiput is low and the cranium is moderately arched upward to the parietal eminence ; the brain-case is full and broad, but the postorbital constriction is not very conspicuous, owing to the very moderate expansion of the forehead, which is but slightly convex. No sagittal crest is present, but a faintly marked sagittal area may be traced over nearly the entire length of the cranium ; the area is narrowest in the frontal region, expanding pos- teriorly, and in one of the skulls (No. 9,250) its hinder margin curves downward and then forward, becoming continuous with the dorsal border of the zygomatic arch and thus demarcating the area of the temporal fossa in a manner which is unusual in the Santa Cruz Gravigrada, but very common among the Pleistocene genera. EDENTATA OF THE SANTA CRUZ BEDS. 245 Laterally, the occipital crest is quite prominent, but it dies away dor- sally ; the supraoccipital is reflected far over upon the dorsal side of the cranium, especially in one of the specimens (No. 9,293) in which this reflection is carried to an unusual extent; the condyles are small and nearly sessile and the paroccipital processes are obsolete. The squa- mosals and frontals do not differ in any important manner from those of H. elongatus, while the lachrymals are rather smaller and less prominent. The nasals are broad posteriorly, where their sutures with the frontals form two straight lines meeting at a very open angle; anteriorly they have blunt median points and deep lateral notches, making very long lateral processes, which project beyond the edge of the anterior nares. The premaxillaries are of the type usual in this genus, but with certain characteristic features ; they are distinctly shorter and heavier than those of H. elongatus, the postero-external branch is heavier, the spine is more slender and the anterior branch is shorter. The maxillaries differ little from the other small species of the genus, except that they have a shorter facial portion than in H. elongatus and that, usually, the preorbital fossae are narrow and shallow. The palatines are very thick and a peculiar, smooth surface slopes upward and backward from the level of the palate to the margin of the posterior nares ; this surface is variable in extent and is much more distinctly shown in some individuals than in others. The hard palate is of nearly uniform width between the molariform teeth, the two series of which are almost parallel ; the degree of roughness and con- vexity of this region varies much, perhaps according to the age of the individual. The front margin of the posterior nares is placed somewhat farther back than in most of the species. The mandible is still incompletely known ; its most characteristic feature is the position of the postero-external opening of the dental canal, which presents laterally and is placed at the base of the ascending ramus. From the length of the premaxillaries it may be inferred that the predental beak was short. MEASUREMENTS. Type. No. 9,293. No. 9,250. Skull, length in median line, including premaxillae .126 " excluding " 105 .108 .105 " occipital condyle to anterior nares 124 .128 .124 to end of premaxillae . 1 36 Cranium, length occipital condyle to edge of orbit 094 .099 .094 Face, length orbit to anterior nares 034 .03 1 .034 246 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. Type. No. 9,293. No. 9,250. Occiput, height -036 .040 " width at base .050 .05 1 Distance, occipital condyle to glenoid cavity 021 .022 .023 « " « » &. 062 .065 .060 Skull, width at postorbital constriction .027 .028 " " over lachrymals .046 .047 Zygomatic arch, length .068 .071 .066 Palate, length in median line 044 .043 .045 " width at 1 017 .018 .016 « « « preorbital fossae 021 .020 .020 " " « S. oio .0125 .010 " " "6. OIO .OI3 .Oil The skeleton, which is known only from the American Museum speci- men, No. 9,250, closely resembles that of H. elongatus, except in its distinctly smaller size. The vertebrae are somewhat smaller than in the latter, but have relatively more robust neural spines, especially in the lumbar and posterior part of the thoracic regions. In the hinder part of the thoracic region the foramina opening on the ventral side of the centra are reduced to very small proportions, in fact, almost obliterated, while in the lumbar region they remain open, reaching their maximum size in the third vertebra of this series. As in H. elongatits, the sacrum consists of five vertebrae, the neural spines of which are coalesced into a continu- ous ridge with thickened dorsal border. The caudal vertebrae are rela- tively somewhat heavier than in the last named species and have slightly longer and heavier transverse processes. The comparatively unimportant differences between the vertebrae of the present species and those of H. elongatus may be largely due to differences of age. MEASUREMENTS. First thoracic, length of centrum 018 Third thoracic, height of neural spine .030 " " width of anterior face .. .014 " " width of neural spine " " " " posterior face . .015 at base 012 " " " " over transverse " " width of neural spine processes .... ? .033 at tip oio " height of neural spine. ?.O3i Last thoracic, length of centrum 022 " width of neural spine at width of anterior face . . .024 base on " " " over transverse Third thoracic, length of centrum ... .016 processes 047 " " width of. anterior face . .012 " " height of neural spine . .038 " " " posterior face .034 " " width of spine at base . .017 EDENTATA OF THE SANTA CRUZ BEDS. 247 Last thoracic, width of neural spine at tip 019 First lumbar, length of centrum 023 " " width of anterior face 024 " " " " posterior face . . . .026 " " " over transverse processes 049 Second lumbar, length of centrum 025 " width of anterior face .025 " " " " posterior face .026 " " " over trans- verse proc- esses 046 Third lumbar, length of centrum 026 width of anterior face . . . .026 width over transverse pro- cesses 048 " height ot neural spine . . .039 Fourth lumbar, length of centrum 026 " " width of anterior face . . .027 " " " over transverse processes 054 " " height of neural spine . . .040 Sacrum , length 119 First sacral, width of anterior face 030 Fourth sacral, width of posterior face . . .027 First caudal, length 022 MEASUREMENTS. First caudal, width of anterior face 030 " " " over transverse pro- cesses 085 Second caudal, length of centrum 022 " " width of anterior face . . .026 " " " over transverse processes 08 1 Third caudal, length of centrum 022 " " width of anterior face . . . .026 " •' " over transverse pro- cesses 076 Fourth caudal, length of centrum 022 " " width of anterior face ... .022 " " " over transverse pro- cesses 068 Fifth caudal, length 022 " " width of anterior face 021 " " over transverse pro- cesses 068 Sixth caudal, length 023 " " width of anterior face 020 " " " over transverse pro- cesses 063 Seventh caudal, length 022 " " width of anterior face . . .018 " " " over transverse processes 059 In the humerus (Plate XLII, fig. 4), the differences from H. elongatus are but trifling; although this bone is actually shorter than in the latter species, its relative length, as compared with that of the skull, is nearly the same, and the proximal portion is somewhat heavier; the bicipital groove is rather more distinctly marked and the inner border of the deltoid area is extended proximally almost to the head, not dying away so gradually as in the other species. The supinator ridge is hardly so broad as in H. elongatus, but has a thicker free border and the trochlear facet for the radius is somewhat less convex ; the supratrochlear fossa is decidedly smaller and shallower and the anconeal fossa very much more so. The fore-arm bones (Plate XLII, figs. 5, 6) also differ very little save in size from those of H. elongatus; the ulna is somewhat more curved in both directions, especially laterally, while the radius has a somewhat 248 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. larger proximal facet for the ulna and a less prominent bicipital tubercle, and the inner border of the distal half of the radial shaft is somewhat more distinct. MEASUREMENTS. Humerus, length 1 29 Ulna, width at sigmoid notch 0195 " width of proximal end 037 " " of distal end oio " " " trochlea 027 Radius, length 1 1 1 « " over epicondyles 050 " width of proximal end 019 Ulna, length 128 " " " distal end 023 " of olecranon 020 " greatest width of shaft 020 The pelvis (see text-figure 21, p. 170) is very similar to that of H. elongatus, with a few differences. The ilium is somewhat more everted, making the acetabular border more concave, and has a more curved crista ; the acetabulum is smaller and more circular and the fossa for the round ligament is less extensive ; the obturator foramen is of a different shape, the dorso-ventral diameter being greater and the antero-posterior diameter less ; the descending process of the ischium, behind the obturator foramen, is more slender and the symphysis appears to be somewhat shorter. MEASUREMENTS. Pelvis, length 190 Acetabulum, antero-posterior diameter .032 " greatest width 225 " dorso-ventral diameter . . .027 Ilium, length 114 Ischium, length 076 " greatest width 080 Symphysis, length 039 In the femur (Plate XLII, fig. 7) the head is more oblique, directed more proximally and rising higher above the level of the great trochanter than in H. elongatus ; the pit for the round ligament is smaller and shal- lower ; the second trochanter is rather more prominent and the third tro- chanter broader proximo-distally ; the condyles are of similar shape, but even less prominent, so that the notch between them is smaller. The tibia (Plate XLII, fig. 8) is almost a copy pf that of H. elongatus, on a somewhat reduced scale ; the facets for the femoral condyles are a little more closely approximated and the spine slightly more pronounced, while the cnemial process is even more reduced. The shaft and distal end differ in no significant way, but the postero-internal margin of the astraga- lar facet is more prominent and the intercondylar ridge less so. The fibula (Plate XLII, fig. 8) differs from that of H. elongatus rather more than does the tibia ; the proximal end is thicker antero-posteriorly EDENTATA OF THE SANTA CRUZ BEDS. 249 and the shaft is more slender; the distal facet for the tibia is smaller and that for the astragalus more nearly plane. The astragalus is less grooved than in the last named species, which is due principally to the smaller development of the inner condyle ; the neck is distinctly shorter and the internal calcaneal facet is smaller and some- what better demarcated from the navicular facet on the plantar side of the neck. MEASUREMENTS. Femur, length from head 1 50 Tibia, thickness of distal end 020 " " " great trochanter. . . .150 Fibula, length 109 " width of proximal end 056 " width of proximal end. 014 " " " distal end over tuberosi- " thickness of proximal end 017 ties 048 " width of shaft in middle 007 " " " condyles .045 " thickness of shaft in middle 009 Tibia, length 119 " width of distal end 020 " width of proximal end 046 " thickness of distal end 018 " thickness of proximal end 035 Astragalus, length 029 " width of shaft in middle 018 " width of trochlea 020 " thickness of shaft in middle 012 " " " distal end 015 HAPALOPS GRACILIDENS Ameghino. (Plates XLIV, Figs. 2, 2", 2b, 2" ; XLV, Fig. 4.) Hapalops gracilidens Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, P- 3i7- In the Princeton collection, this species is represented by two skulls, without mandibles, which were found by Mr. Hatcher, one (No. 15,529) at Killik Aike, and the other (No. 15,525) at Lake Pueyrredon ; the latter has been considerably distorted by lateral pressure, which much exag- gerates the difference between the two specimens. The teeth are strikingly small even in proportion to the small size of the skull, and this is especially true of the individual from Lake Pueyrre- don. The first upper tooth (-) is subcylindrical and relatively large, its alveolus forming quite a prominence upon the side of the face ; the dia- stema is short and the molariform teeth (-".-) are of transversely rectangu- lar shape ; - is slightly larger than the others, while - is extremely small, particularly so in the type. The teeth of the two sides form paral- lel rows. 250 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. MEASUREMENTS. Type. No. 15,525. No. 15,529. Upper dentition, length .037 " " " 1-A 023 .022 -0235 1, length (i. t., antero-posterior diameter) .006 " width (/. e., transverse diameter) : .004 1, length .005 .005 "width .006 .0055 3, length .0055 .0055 " width .0065 .007 A, length .0045 .005 " width .006 .0065 i, length .003 .003 5 " width 004 .005 .005 In appearance and proportions the skull is one of the most peculiar to be found in the present genus and the peculiarities are best displayed in the Killik Aike specimen (No. 15,529), (Plate XLIV, fig. 2). The occi- put is both broad and high and the cranium is strongly vaulted ; from the parietal eminence, which is longer than usual and extends forward to the frontal suture, there is a steep descent forward to the forehead and thence a very slight descent to the end of the rostrum ; the contrast in dorso- ventral height between the cranial and facial regions is thus very marked. An occipital crest can hardly be said to exist, and the sagittal crest is either entirely absent (No. 15,525) or very feebly indicated on the frontals only (No. 15,529), in which case it is associated with a sagittal area on the parietals ; the supraoccipital is very extensively reflected over upon the dorsal surface of the cranium, especially in the Lake Pueyrredon specimen. The parietals form more of the cranial walls than usual, while the squa- mosals are relatively small ; the frontals have less of an hour-glass shape than in most species of the genus, for the expansion in front of the post- orbital constriction is slight and very gradual. The maxillaries have no especially characteristic features except the small size of the preorbital fossae and the flatness of the palate. MEASUREMENTS. No. 15,525. No. 15,529. Skull, length from foramen magnum to anterior nares ?. 106 Cranium, length from foramen magnum to edge of orbit 087 .084 Face, length orbit to anterior nares P.O22 Occiput, height 036 .032 " width at base 043 043 EDENTATA OF THE SANTA CRUZ BEDS. 251 MEASUREMENTS. No. 15,525 No. 15,529 Skull, width at postorbital constriction 026 .029 " " over lachrymals .041 Zygomatic arch, length 055 .054 Palate, width at -1 .012 " " " preorbital fossae .018 " " "2 on .012 " " "£..._. on .on HAPALOPS FORTICULUS Ameghino. Psetidhapalops forticulus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 319. Pseudhapahps altiramis Amegh. ; 6num. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 150. The most characteristic feature of this species is to be found in the shape of the lower caniniform tooth (-) which is large and laterally com- pressed and projects from the side of the jaw almost as much as in some of the species of Eucholaops. The mandible has an extremely short pre- dental beak and the profile of the chin curves uninterruptedly into the ventral border of the horizontal ramus, the two together describing a con- siderable segment of a circle. The postero-external dental foramen is large and opens laterally, not anteriorly, and is placed in an unusually inferior position, upon the side of the horizontal ramus below the base of the coronoid. In the collection of the La Plata Museum is a portion of the lower jaw which agrees quite exactly \vith the type of the present species. The specimen to which Ameghino has given the name Pseudhapahps altiramis (loc. cit., p. 150) appears to be merely a more robust and older individual of the present species, with lower caniniform of more triangular and less laterally compressed shape. MEASUREMENTS. Type. P. altiramis. Lower dentition, length 039 .037 " " " j_j 022 .023 T, length (i. e., antero-posterior diameter) 007 .007 " width (i. e., transverse diameter) .005 j, length 0065 .006 7, length 006 .006 " width 009 252 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. MEASUREMENTS. Type, P. altiramis. j, length oo8 " width oio Depth of jaw at ff 025 .025 HAPALOPS GRANDIS Ameghino. Pseudhapalops grandis Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 151. This appears to be a fairly well characterized species, despite its varia- bility in certain respects ; it resembles the preceding one in the form of the jaw, but is very much larger. The species is represented by three specimens in the Ameghino collection and by a fourth in the La Plata Museum. In the type T is of moderate size, in a second individual it is smaller and more cylindrical, and in a third it is much compressed, the cross-section suggesting the canine of a small machairodont. The pre- dental beak of the mandible is longer than in H. forticulus, but otherwise the shape of the jaw and the position of the postero-external dental fora- men are much as in the latter. MEASUREMENTS. Lower dentition, length 045 Mandible, length from condyle 120 " " " jj._? 029 " of predental beak 032 T length (i. e., antero-posterior diameter) .006 depth below ^ 033 " width (i. e., transverse diameter). ... .005 HAPALOPS LONGITUDINALIS Ameghino. Pseudhapalops longitudinalis Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 319. Although known only from a single fragment of the lower jaw, this is probably a valid species, unless it should prove to be merely an indi- vidual abnormality. It is characterized by the very exceptional shape of T, which, instead of being cylindrical or transverse, as it is in all of the other known species of the genus, is elliptical with the major axis in the antero-posterior direction. MEASUREMENTS. Lower dentition, length ?_T 0245 ff, width ... .008 5-, length (i. e., antero-posterior diam- 3, length 008 eter) 007 " width 006 2, width (i. e., transverse diameter). . . .0085 Depth of jaw below 5 024 j, length 0065 EDENTATA OF THE SANTA CRUZ BEDS. 253 The skulls of Gravigrada, six in number, which Mr. Hatcher collected at Lake Pueyrredon, appear with one exception, to belong to species dif- ferent from those which have been found on or near the Atlantic coast. The specimens, all of which are in a hard concretionary matrix, are not in a very satisfactory state of preservation and have suffered more or less distortion from pressure. No two individuals are alike and, in the absence of much more extensive materials, it is extremely difficult to determine how many species are represented. The exception noted above is a small skull (No. 15,525) which agrees very well with H. gracilidens from the coast region. Of the others, one is a very well marked species and is described below as H. vulpiceps, and the remaining four may be provisionally assigned to one species, H. platycephalus, for, though they are quite dissimilar in size and -appearance, these dissimilarities are evi- dently in part due to differences of age, in part t6 the varying direction and amount of the pressure to which they have been subjected ; the remaining differences should probably be ascribed to the variability which is so striking in the entire group. HAPALOPS VULPICEPS sp. nov. (Plate XLIV, Figs, i, la, \b.} In the proportions of the skull this species differs notably from all other known Santa Cruz Gravigrada, rather resembling, especially in side-view, the skull of a carnivore. Of the dentition, the upper series is represented by -, broken to the level of the jaw, - and - intact and the empty alveoli of ^ and -; all the lower teeth are preserved in a more or less broken condition. The upper caniniform (-) is relatively large and, though separated from 4 by a considerable diastema, is yet implanted unusually far behind the anterior end of the palate, farther than in any other species of the genus ; in cross section this tooth is a longitudinal, much compressed oval ; - is relatively small and of transversely oval form; - and -, which were evidently much larger than -, were apparently of almost equal size, and - is small and much compressed antero-posteriorly. In the mandible T is small, obscurely trihedral, with two faint vertical grooves, which demar- cate an external pillar; 2 and ^ are quite large 'and transversely rect- angular, while T has the usual subcylindrical shape. 254 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. MEASUREMENTS. Upper dentition, length 0425 £, width 006 " " " i-6- 025 Lower dentition, length 0335 i, length (i. e., antero-posterior di- " " " z_4 023 ameter) 0075 T> length 0045 " width (/. e., transverse diameter) . . . .004 " width 004 1, length 005 j, length 0065 " width 007 " width 008 2, length 007 -s> length 0065 " width 0085 " width 008 A, length 007 ?, length • 007 " width 008 " width 007 A, length 003 As already remarked, the skull has a highly characteristic appearance. The cranium is long, broad and quite low, the upper contour rising but slightly from the summit of the occiput to the inconspicuous parietal emi- nence ; the postorbital constriction is long, but not deep, the forehead is gently convex and the preorbital region, or rostrum, unusually long, narrow and tapering. It is this elongate, tapering rostrum which, more than any other feature, gives its peculiar appearance to the skull. The sagittal crest is feebly developed and only upon the frontals in the region of the postorbital constriction. The occiput is low and broad, somewhat inclined forward, and decidedly convex in both directions, with a median prominence which lodges the vermis; the condyles are quite large and prominent, but the paroccipital processes appear to be entirely obsolete. In marked contrast to nearly all the other species of Hapalops, the supra- occipital is hardly at all reflected upon the dorsal side of the cranium. The parietals, which are large, have no sagittal crest, but, on the contrary, a well defined groove along the sagittal suture, and an ill-defined sagittal area, which is broadest in the middle and narrows both before and behind. The zygomatic process of the squamosal is much swollen at the base, indicating an unusually large sinus. The tympanics, frontals and lachrymals do not differ in any significant way from those of the other species of the genus. The nasals are narrow and elongate; they are broadest at the frontal suture and narrowest about the middle of their course, expanding again at the anterior end, where they show the usual lateral notches. The maxillaries have an elongate facial portion, in front of the orbits, and the preorbital fossae are very shallow ; the hard palate EDENTATA OF THE SANTA CRUZ BEDS. 255 is moderately convex and of uniform width between the molariform teeth, while the anterior part is flat and relatively narrow, in correspondence with the slenderness of the rostrum. The mandible, which is represented only by the horizontal rami, lacking the predental beak, is characterized by the external dental foramen, which presents laterally rather than anteriorly and is placed at the base of the coronoid process, somewhat more elevated than in H. forticiilus and lower down than in most species of the genus. MEASUREMENTS. Skull, length in median basal line 109 Distance • occipital condyle to glenoid " occipital condyle to anterior cavity. .021 nares 127 " " " "A 062 Cranium, length condyle to edge of orbit .095 Palate, length in median line 046 Face, length orbit to anterior nares 032 " width at 1 016 Occiput, height 036 " " " preorbital fossai 018 width at base 050 " " " 1 oio Skull, width at postorbital constriction . . .030 " " " & oil " over lachrymals 044 Mandible, depth below -j 023 Zygomatic arch, length 065 " thickness below y 013 HAPALOPS PLATYCEPHALUS sp. nov. (Plate XLV, Figs. 1-3".) As the type of this species No. 15,564 will be taken, for that is the most mature and best preserved individual of the series, although it has suffered from oblique distortion. H. platycephalus is one of the smaller species of the genus, about equalling H. elongatus in size, but decidedly more robust ; it may be recognized by the short diastema between A and a, the unusually flat palate, the short, wide rostrum, with deep preorbital fossae, the broad, depressed cranium, without sagittal crest, and the low, wide occiput, with very inconspicuous occipital crest. The teeth are of the pattern common throughout the genus ; i is not preserved in any of the specimens, but the alveolus shows that it was small and longitudinally oval ; this tooth appears to have been inserted well behind the anterior edge of the palate, but the broken condition of all the skulls renders this somewhat uncertain. After a rather short diastema follows ^, which is ordinarily quite small and transversely rect- angular ; £ is the largest of the series and -*- is slightly larger than £ ; ^ is much reduced. The lower teeth, which are preserved only in the type, have no striking peculiarities. 256 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. MEASUREMENTS. No. 15,564.. No. 15,534.. No- J5,522- Upper dentition, length 044 « « « 3.-A 026 .025 .026 1, length (i. e., antero-posterior diameter) 007 " width (/'. e., transverse diameter) 0065 i, length 0055 .005 .0055 " width 007 .0065 .008 i, length - 006 .006 .005 " width 0085 .008 .0085 A, length 005 .005 .005 " width 008 .008 .007 £, length 003 .0035 .004 " width .006 .006 .007 The following measurements are from the type-specimen, No. 15,564. Lower dentition, length 036 ^, width 008 j_¥ 022 3, length 006 T, length 006 " width 008 " width 005 T, length 0075 j, length 0053 " width 007 The general characters of the skull have been given in the diagnosis of the species and it remains only to mention some of the more important details. The occiput is unusually low and wide, and is nearly vertical, with a broad median convexity, which is especially distinct in the fully mature individual ; near the dorsal border of this convexity appears a median ridge, which extends for a short distance upon the dorsal side of the cranium ; the foramen magnum is small, as are also the nearly sessile condyles ; no paroccipital processes are apparent. The occipital crest is weakly developed, dying away dorsally, but be- comes more distinct with age ; the supraoccipital is reflected upon the dorsal side of the cranium to an unusual degree, much less, however, in No. 15,522, which is the most aberrant of the series and may pertain to another species. The broad, vaulted parietals show no trace of a sagittal crest and only an obscurely indicated sagittal area. The forehead is broad and nearly flat and the postorbital constriction is very shallow ; the sagittal crest is absent from the frontals of all but the oldest individual, in which it is feebly developed. The nasals are very wide, especially at the hinder end, where they describe the segment of a circle, quite deeply EDENTATA OF THE SANTA CRUZ BEDS. 257 emarginating the frontals. The preorbital fossae are shallow, except in No. 15,522, in which they are well defined. Of the mandible only a fragment of the left ramus, belonging to the type, is preserved ; it seems to be of more uniform dorso-ventral depth and to be less thickened in the dentary region than is usual in this genus. In the following measurements it should be observed that the type- specimen (No. 15,564) has been made unduly low and wide by crushing. MEASUREMENTS. No. 15,564. No. 15,534. N°- J5,522. Cranium, length occipital condyle to edge of orbit. .. .108 .096 .101 Occiput, height 035 .034 .036 " width at base 055 .049 .050 Cranium, width at postorbital constriction 036 .030 .030 " " over lachrymals 060 Zygomatic arch, length . .075 .064 .070 Distance, occipital condyle to glenoid cavity 027 .026 " " " " £ 071 .065 Palate, width at 1 020 .022 " " preorbital fossae 023 .019 .020 " " & 014 .011 .0125 " £ 013 .010 .013 Mandible, depth below 3- 023 thickness below 7 013 Associated with the type are a number of fragmentary vertebrae and of limb-bones in better preservation. The latter are of about the same length as in H. elongatus, but considerably stouter. The humerus is quite robust, with more prominent deltoid ridge than in the last named species, larger epicondylar foramen and much shallower supratrochlear fossa. The femur differs from that of H. elongatus in only a few particulars ; the head is larger, the neck less distinct, the great trochanter smaller and the digital fossa even shallower ; the second trochanter is rather more promi- nent and the third broader proximo-distally ; the shaft is broader and the rotular groove and intercondylar notch are wider. The tibia is some- what heavier and more curved. MEASUREMENTS. Humerus, length 152 Humerus, width of trochlea 031 width of proximal end 039 Femur, length from head 168 " shaft below deltoid " great trochanter .. .161 area 020 " width of proximal end 063 258 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. MEASUREMENTS. Femur, width of distal end over condyles .049 Tibia, thickness of proximal end ....... 040 " " " rotular groove ........ 025 " width of shaft in middle ......... 020 Tibia, length ....................... 123 " thickness of shaft in middle ...... 015 " width of proximal end ...... ... .050 " " " distal end .......... 022 In addition to the foregoing species of Hapalops, which may be regarded as more or less well defined, several species have been named, concerning which I could arrive at no definite conclusion, either because, at the time of my visit to La Plata, the types were inaccessible, or because the material was insufficient for determination. In the following list of these supposed species they are all referred to Hapalops, though some of them may prove to belong to different genera. HAPALOPS ADTEGER Ameghino. Eucholceops adteger Amegh. ; Enumeracion sistematica, etc., 1887, p. 23. Eucliolozops adteger Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent., 1889, p. 694. Hapalops adteger Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. Eurysodon adteger Mercerat; Rev. del Mus. de La Plata, T. II, 1891, p; 20. Hapalops adteger Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 145. Hapalops adteger Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 198. HAPALOPS CRASSIDENS Ameghino. Hapalops crassidens Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 136- Hapalops crassidens Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonia ; 1894, p. 146. Hapalops crassidens Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 198. HAPALOPS DIVERSIDENS Ameghino. Hapalops diver sidens Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, P- EDENTATA OF THE SANTA CRUZ BEDS. 259 Hapalops diversidens Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie ; 1894, p. 145. Hapalops diversidens Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 198. HAPALOPS LONGIPALATUS Ameghino. Hapalops longipalatus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, P- 3i7- Hapalops longipalattis Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 145. Hapalops longipalatus Amegh. ; Sec. Censo de la Repub. Argent, T. I, 1898, p. 198. HAPALOPS DEPRESSIPALATUS Ameghino. Hapalops depressipalatus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 317. Hapalops depressipalatus Amegh. ; Enum, Synop. des Mamm. Foss. de Patagonie ; 1894, p. 146. ops depressipalatus Amegh. ; Sec. Censo de la Repub. Argent. T. I., 1898, p. 198. HAPALOPS TESTUDINATUS Ameghino. ops testudinatus Amegh. ; Rev. Argent de Hist. Nat, T. I, 1891, p. 318. Hapalops testudinatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 146. Hapalops testudinatus- Amegh. ; Sec. Censo. de la Repub. Argent., T. I, 1898, p. 198. HAPALOPS CRASSIGNATHUS Ameghino. Hapalops crassignathus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 318. Hapalops macrognathus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 145. Hapalops macrognathus Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 198. 260 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. HAPALOPS MINUTUS Ameghino. Hapalops minutus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 318. Hapalops minutus Amegh. ; Enum. Synopt. de Mamm. Foss. de Pata- gonie; 1894, p. 146. Hapalops minutus Amegh. ; Sec. Censo de la Repub. Argent. ; T. I, 1898, p. 198. HAPALOPS AUSTRALIS (Mercerat). Stenocephalus anstralis Mercerat; Rev. del Mus. de La Plata, T. II, 1891, p. 10. Hapalops indifferens Amegh., in part; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 145. HAPALOPS COGNATUS (Mercerat). Stenocephalus cognatus Mercerat; Rev. del Mus. de La Plata; T. II, 1891, p. 11. Hapalops rectangularis Amegh., in part; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 144. HAPALOPS BOULEI (Mercerat). Eurysodon bottlei Mercerat; Rev. del Mus. de La Plata; T. II, 1891, p. 21. Xyophorus sulcattts Amegh., in part; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 155. HAPALOPS ROSTRATUS (Mercerat non Ameghino). Eurysodon rostratus Mercerat; Rev. del Mus. de La Plata; T. II, 1891, p. 22. HAPALOPS LATUS (Ameghino). Amarorhynchus latus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 147. Amarorhynchus latus Amegh. ; Sec. Censo de la Repub. Argent. ; T. I, 1898, p. 199. HAPALOPS CRASSISSIMUS (Ameghino). Xyophorus crassissimus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 156. Xyophorus crassissimus Amegh. ; Sec. Censo de la Repub. Argent., T. I., 1898, p. 200. EDENTATA OF THE SANTA CRUZ BEDS. 26 1 HAPALOPS PRIMUS (Ameghino). Mecorhimis primus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 157. Mechorhinus primus Amegh. ; Sec. Censo de la Repub. Argent. ; T. I, 1898, p. 200. It may seem quite incredible that so many as twenty-two species of a single genus should have coexisted in the same region, but there are many independent reasons for believing that they did not all exist at the same time. A more minute study of the Santa Cruz beds than has yet been practicable will very probably demonstrate their divisibility into several zones, each characterized by its own species. Further, it should be re- membered that the twenty-two species of Hapalops admitted in the pre- ceding pages are of a very provisional character, and that more extensive and better preserved material may necessitate the union of many of these so-called species. Even with that now at command, it is obvi- ous that there are several groups of species, the members of each group or series being more nearly connected with one another than with those of other groups. One such series, characterized by broad cranium and rostrum, elongate premaxillaries and predentary beak of the mandible, is composed of H. rectangularis, indifferens, longiceps, robustus, aguirrei and brachycephalus ; a second series, with long and narrow skull, short pre- maxillae and mandibular beak, is made up of H. elongatus, rostrattis, atlanticus, ruetimeyeri, gracilidens, and angustipalatus and other similar series might be readily constructed. It is not at all impossible that it may become necessary to unite these twelve supposed species into two, and yet this is not likely, both on account of the stratigraphic reasons, and because of the great differences of size which such a fusion would involve. Decide these questions as we may, the variability of the species of this genus is most surprising. HYPERLEPTUS Ameghino. (Plate LIV, figs, i, i°) Hyperleptus Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 155. f Eucholczops Amegh., in part; Ibid., p. 323. Hyperleptus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 151. 262 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. ? Pseud hapalops Lydekker, in part ; Anales del Mus. de La Plata ; T. Ill, 1894, p. 100. This genus is very closely allied to Hapalops and should perhaps be united with it ; for the present, however, it will be preferable to keep it distinct, because of the lack of transitional specimens. The only diagnos- tic character of Hyperleptus is the peculiar shape of the premaxillae, which form short, broad, triangular plates, with the apex directed forward ; the change is due to the relatively great broadening of the postero-external branch of each premaxillary, whereby the incisive foramina are reduced to very narrow slits ; the surfaces on the maxillaries for articulation with the premaxillae are also characteristic. The preorbital fossae are very deep, producing a marked constriction of the palate at the diastema between - and -, while the alveoli of the upper caniniform teeth are so prominent as to produce a strikingly broad muzzle, much as in Rucholczops. The postero-external opening of the dental canal (external dental foramen) is on the horizontal ramus at the base of the coronoid. HYPERLEPTUS GARZONIANUS Ameghino. (Plate LIV, Figs, i, 10.) Hyperleptus garzonianus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 155. ? Euchofaops fissognatkus Amegh. ; Ibid. p. 323. ? Hyperleptus schissognathus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 152. ? EiicJwlceops litoralis Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 322. ? Hyperleptus litoralis Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 152. f Pseud I lap atop s ntetimeyeri Lydekker, in part ; Anales des Mus. de La Plata, T. Ill, 1894, p. 101. The type-specimen in the Ameghino collection has been considerably altered in appearance by lateral compression, which renders the skull un- duly narrow and exaggerates the apparent development of the sagittal crest. The teeth display but few differences from those of Hapalops ; the upper caniniform (-) is of moderate size and subcylindrical shape ; it is implanted a very short distance behind the anterior border of the max- EDENTATA OF THE SANTA CRUZ BEDS. 263 illary and its external face projects well outside the line of the other teeth, almost as much as in Eucholceops. The diastema between 1 and i is longer than in most species of Hapalops. Of the.molariform teeth, a, - and A are transversely oval, differing only in size, * being the broadest transversely and shortest antero-posteriorly ; ^ is nearly cylindrical, which is a very unusual feature, though materials are lacking to determine whether this is an individual abnormality, or whether it is truly charac- teristic of the species. In the mandibular dentition the resemblance to Hapalops is even closer; - is high, erect and bevelled by attrition and the diastema is quite short, much shorter than in the upper jaw ; 2 and -5 are transversely oval and T, which is unusually large, is of the ordinary, subcylindrical shape. MEASUREMENTS. Upper dentition, length 067 5-, width 009 " " " S--&- 039 Lower dentition, length 048 J-, length (/'. e., antero-posterior di- " " " ^_f 030 ameter) 009 T, length 007 " width (t. c., transverse diameter) 007 " width 006 ^, length 0085 5-, length 008 " width 012 " width 012 &, length 008 3-, length 008 " width 0135 " width 012 A, length 008 5 7, length o i o " width 01 2 " width 0095 i length, 0075 The skull resembles that of Hapalops and, in a somewhat less pro- nounced degree, that of Eucholozops. The occiput is quite high in proportion to its width and the supraoccipital does not extend at all upon the dorsal side of the cranium ; the upper contour of the skull rises very gently from the occipital crest to the parietal eminence, which is incon- spicuous; from that point it pursues a nearly horizontal course to the fronto-nasal suture, whence it descends very gradually to the muzzle. Occipital and sagittal crests are present, but are not very prominent and the latter ends upon the frontals by dividing into two very obscurely marked temporal ridges. The preorbital or facial region is relatively long and high and the preorbital fossae of the maxillaries are very deep on the ventral side, where they notably constrict the palate, but become very shallow dorsally, so that they are hardly visible from above. The nasals 264 PATAGONIAN EXPEDITIONS '. PALAEONTOLOGY. are quite long and broaden anteriorly, where they are curved downward at the sides and abruptly truncated, except that each has a broad and very shallow notch, entirely different from the deep and narrow lateral notches of Hapalops. The premaxillae are short, broad behind, narrow- ing forward and ending in a blunt point; together they form a broad, heavy, triangular and almost solid plate of bone, the incisive foramina being reduced to narrow slits. The premaxillary facets on the maxillaries are equally characteristic; that for the postero-external branch occupies nearly the entire width of each maxillary, while the median notch of the palate which receives the premaxillary spines is very narrow and shallow, quite unlike that seen in any other genus. The zygomatic arch does not differ in any important respect from that of Hapalops and the jugal, with its long suborbital process, is quite as in that genus. The mandible has a rather elongate horizontal ramus, the ventral border of which is but slightly convex, in marked distinction from that of Hapalops, and the concavity beneath the ascending ramus is correspond- ingly slight. The symphysis is short and the profile of the chin is thus quite steep ; nevertheless, the predental beak is quite elongate and con- tracts anteriorly to a rounded edge, which is notched in the median line. MEASUREMENTS. Skull, median basal length, including Palate, width at ^ 017 premaxillary .200 " " " &- 014 " " " excluding Mandible, length of predental beak 040 premaxillary .186 " depth below ^ 036 Palate, width at 1 025 thickness below 3 029 HYPERLEPTUS SECTUS Ameghino. Hyperleptiis sectus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 155. This species is closely allied to the preceding one and may prove to be identical with it. It is distinguished by the form of the last upper tooth, £, which is transverse and not subcylindrical, and by the much more decided constriction of the palate. The very broad muzzle, with its pro- jecting caniniform teeth, emphasizes the likeness to Rucholccops. The premaxillaries are not known, but the facets for them upon the maxillaries are quite as in H. garzonianus. The following measurements are from the type-specimen in the Ameghino collection. EDENTATA OF THE SANTA CRUZ BEDS. f 265 MEASUREMENTS. Upper dentition, length 069 A, length 008 £-& 038 " width 012 i, length (i. e., antero-posterior diameter) .008 &-, length 006 " width (i. e., transverse diameter) 006 " width oio ^, length 009 Palate width at 1 025 "width 012 i 015 £, length 0085 " "*- 014 " width 013 Muzzle, width over J- 042 EUCHOLOEOPS Ameghino. (Plates LV-LVII.) Eitcholccops Amegh.; Enumeracion sistematica, etc., 1887, p. 21. This genus is nearly allied to Hapalops, which it resembles in all parts of the skeleton, the constant differences between the two genera being almost confined to the dentition and skull. Specimens of Eucholczops are very much less common in the Santa Cruz beds than those of Hapalops and there is no such abundance of species as in the latter, but we meet with the same variability and the same difficulty in making any satisfac- tory systematic arrangement. In the dentition, the characteristic feature of the genus is to be found in the first tooth of each jaw, which is large, prominent and caniniform, usually pointed by abrasion and placed externally to the line of the other teeth. Some individuals show signs of what may be sexual differences in the size of these teeth, which are considerably larger in certain specimens than in others which differ from the former in no other respect; i is implanted close to the anterior border of the maxillary and is always fol- lowed by a relatively long diastema. The molariform teeth resemble those of Hapalops in shape, being transversely oval or obscurely rectangu- lar and grooved by a deep valley. The skull has a similar general appearance to that of Hapalops, but with a number of constant and characteristic differences ; it is shorter in proportion and quite conspicuously broad and heavy; the sagittal and occipital crests are much better developed and in some of the species are very prominent, less so in others, and the supraoccipital is little or not at all reflected over upon the dorsal side of the cranium. The muzzle is very broad, expanding anteriorly and, except for the premaxillae, abruptly truncated ; the facial portion of the maxillary is not continued in front of 266 PATAGONIAN EXPEDITIONS : PALEONTOLOGY. the caniniform tooth, as it is in almost all other Gravigrada of the Santa Cruz, but forms a rounded, massive, pillar-like alveolus for this tooth in a highly characteristic manner ; the preorbital fossae are broad and on the ventral side are very deep, but they do not extend to the dorsal side of the rostrum and hence the constriction is much more striking when the skull is seen from below. The mandible is very characteristic; the horizontal ramus is short and deep, very thick and massive and usually the alveolus of the caniniform projects outward as a prominent pillar; in front of this pillar is a deep notch, which receives the upper caniniform ; the predental beak is very short, but narrowing forward rapidly and terminating in a blunt point ; however, there is considerable variation in the shape of this beak, even in the same species ; it is depressed and but little excavated upon the dorsal side and, in correlation with its shape, the symphysis is short and steep. The ascending ramus is relatively better developed than in Hapalops and the coronoid and angular processes are larger ; the postero-external open- ing of the dental canal is at the base of the coronoid upon the horizontal ramus, the usual position among the Santa Cruz Gravigrada, except in most of the species of Hapalops. So far as it is known, the skeleton agrees very well with that of Hapa- lops, differing only in details of minor importance. As the known parts of the skeleton almost all belong to E. fronto, they will be described in connection with that species. From the material that has been collected it is impossible to reach any very definite conclusions as to the number of species into which Eucho- Iceops should be divided. Lydekker ('94, 95) recognizes but one species1 of this genus, while Ameghino has described six, to which Mercerat has added two. Of these, two are quite distinct, a larger one, E. ingens, and a smaller one, E. fronto ; a third species, E. externus, would undoubt- edly be recognized as valid, if we could be assured that the type and only known specimen were normal. Probably a fourth species, E. cnrtus, also known only from the type, should be accepted, though additional material is necessary to determine this point with certainty. The relationships of Eucholwops are not obscure ; obviously it was de- rived from a common and not remote ancestor with Hapalops and has become specialized by the great development of the caniniform teeth. To 1 E. titan Lydekker is not referable to this genus, but to Prepotkerittm. EDENTATA OF THE SANTA CRUZ BEDS. 267 a certain extent, Hyperleptus may be regarded as intermediate between the two genera named, but its peculiar premaxillaries show that it does not form a member of the same series, but is an offshoot from that series. As regards the connection between Eucholccops and the Pleistocene gen- era, Lydekker has made the following suggestion ('94, 98). "The genus, which is evidently a generalized one, is nearly allied to the ancestral stock of both Mylodon and Megalonyx, if indeed it be not the actual pro- genitor of both." With this suggestion I am unable to agree. Euckolccofis is in all respects a typical member of the Megalonycttida and is no more nearly related to Mylodon than is any other Santa Cruz representative of this family. As will be shown in a later section, genera much more closely allied to the direct ancestor of Mylodon are known in the Santa Cruz fauna, as is also the very probable "actual progenitor" of Megalonyx. Eucholceops, on the contrary, is almost certainly the final term of a series which because extinct at the close of the Santa Cruz epoch. On the other hand, it is undoubtedly true that in Santa Cruz times the three families of the Gravigrada were much less widely separated than they had become, through divergent evolution, in the Pleistocene, and, in that sense, Eucholocops is " nearly allied to the ancestral stock of both Mylodon and Megalonyx" but not more so, it may be added, than to that of Megatherium. EUCHOLOEOPS INGENS Ameghino. (Plate LVII, Figs. 2, 2", 3.) Eucholaops ingens Amegh. ; Enumeracion sistematica, etc.; 1887, p. 21. Eucholaops latirostris Amegh.; Rev. Argent, de Hist. Nat. ; T. I, 1891, p. 322. This, the type-species, is the largest and most massive of the genus, though there is much individual variation in regard to size. In the males, at least, the caniniform teeth are very large, of triangular section and worn by abrasion to a sharp point. The mandible has a short horizontal ramus, which is remarkable for its depth and thickness and for the con- vexity of its ventral border, that of the ascending ramus being concave and at a much higher level, except for the downward curvature of the angular process, which is unusually broad. In the collection of the American Museum of Natural History is a mandible (No. 9,307) which probably pertained to a female of this species and is considerably smaller than the robust animals with large caniniform 268 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. teeth which I have regarded as the males; T is hardly larger than in Hapalops and projects comparatively little beyond the line of the other teeth ; in cross-section it is obscurely trihedral, with the base presenting forward, and is very obliquely worn ; ^ and 7 are broad transversely, com- pressed antero-posteriorly, and T is irregularly cylindrical. The jaw has a much less robust horizontal ramus than that of the supposed male, with less convex ventral border ; the predental beak is very broad at the base and hardly at all notched for -. On each side, near the median line, are two conspicuous mental foramina, one above the other, of which the lower is considerably the larger. MEASUREMENTS. No. 9,307. Male (Amegh. Coll.'). Lower dentition, length 0465 .047 " " " 5-_T 0265 .026 T, length (i. e., antero-posterior diameter) 0055 .008 " width (i. e., transverse diameter) 005 2-, length 007 .007 " width 0105 g-, length 0065 .005 " width 0105 T, length . 009 " width oio Mandible, length from condyle 130 to y, inclusive 099 . 1 14 angle to T, inclusive .122 depth at 3- 036 .044 thickness at 3- 021 height of condyle .062 " " coronoid -074 The following measurements of the type-specimen are taken from Ameghino ('89*, 693-4). Upper dentition, length 071 &, width 0085 Lower " " 055 T, length oil Upper diastema, length 023 " width 014 1, length oil Diastema, lower, length 013 " width oio Lower dentition, length ^_— 031 i, length 0075 Palate, length 070 " width 01 1 " width at i 039 £, length 0075 " " between molariforms 026 " width 012 Skull, length condyle to 1 172 A, length 0075 " width over 1 062 " width 01 25 Mandible, length of beak 035 £, length 006 " depth below molariforms . . .035 EDENTATA OF THE SANTA CRUZ BEDS. 269 EUCHOLCEOPS EXTERNUS Ameghino. (Plate LVI, Fig. i.) Eucholceops extemus Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 322. The type-specimen is a finely preserved skull and mandible in the Ameghino collection and, if its peculiarities are not abnormal, the species is well distinguished. The principal characteristic is given by the shape of the caniniform teeth, which are very large and indicate that the animal was a male ; the lower one bites inside of the upper one, instead of be- hind it, and thus its abraded surface presents outward, not forward as it does in almost all other known Santa Cruz Gravigrada ; similarly the worn surface of - is internal, not posterior. The dimensions of this speci- men are as follows and show that this species is considerably smaller than the preceding one. MEASUREMENTS. Upper dentition, length 060 Lower dentition, length 048 " diastema, length 019 Skull, length condyle to anterior nares. .148 EUCHOLCEOPS PRONTO Ameghino. (Plates LV; LVI, Figs. 2-4 a ; LVII, Fig. I.) E^tct^ol(Eops fronto Amegh. ; Rev. Argent. deHist. Nat., T. I, 1891, p. 322. E^lcholo^ops latifrons Mercerat ; Rev. del Mus. de La Plata, T. II, 1891, p. 15. Eucholaops lafonei Mercerat ; Ibid, p. 16. , The following description is founded upon the types of Ameghino and Mercerat, upon an incomplete skull, with mandible and several bones of the skeleton (No. 9,241) in the American Museum of Natural History, and a second mandible (No. 9,575) in the same collection, and upon a mandible and several vertebrae (No. 15,314) in the Princeton Museum. The dimensions, though variable, are much less than those of E. ingens. The teeth vary considerably in size and shape, apparently even in indi- viduals of the same sex. In the supposed females the caniniforms are quite small and in the type of E. latifrons Mercerat (figured by Lydekker, '94, PI. LIX, fig. 4; LX, i) which is probably a young female, the upper caniniform is very small, laterally compressed and projecting rela- tively little beyond the line of the upper teeth, and of a shape resembling that seen in Hapalops. In the males the caniniforms are large, trihedral and pointed by wear, similar to those of E. ingens in shape, but some- 270 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. what smaller proportionately. The upper molariform teeth are broad trans- versely, much compressed antero-posteriorly and either oval or obscurely trapezoidal ; in the mandible these teeth are more constantly oval. MEASUREMENTS. Type. E. latifrons. E. lafonei. Upper dentition, length 060 .054 .063 " <• « A-.fi. .032 .031 .034 1, length (*'. e., antero-posterior diameter) 008 .008 .0105 " width (/. e., transverse diameter) 006 .005 .008 4( length 0065 .0068 .0065 " width oio .0095 .0095 A, length 007 .007 .0065 "width oil .oil .0105 A, length 006 .007 .006 " width on .010 .010 *, length 005 .005 .005 " width 009 .008 .008 Type. No. 9,241. No. 9,575. No. 15,314.. Lower dentition, length 037 .041 .041 .043 " " " s_4 024 .026 .026 026 T, length 007 .007 " width .006 j, length 006 .007 .007 006 " width .010 .010 .009 y, length 0065 .0065 " width .010 T, length 008 .007 " width .0095 So far as can be judged from the available specimens, the skull resem- bles that of R. externus, with elongate and rather narrow cranium, short and very broad face ; the upper contour of the skull is straighter than in most species of Hapalops, the parietal eminence rising but little above the summit of the occiput. As appears to be always the case in this genus, the occipital crest is much better defined than in Hapalops and the sagit- tal crest, though low and thin, is very distinct and ends anteriorly in rugose temporal ridges. The postorbital constriction is much shallower than in Hapalops, but the preorbital fossae are made very deep by the conspicuous prominence of the caniniform alveoli. The occiput is low and wide, is inclined slightly forward and is almost plane, except for a broad median convexity, which bears near the dorsal EDENTATA OF THE SANTA CRUZ BEDS. 27 1 summit a short and sharp vertical ridge, with a small but deep pit on each side of it ; the condyles are rather small and are separated ventrally by a deep and narrow notch ; the foramen magnum is a vertical oval and the paroccipital processes are quite long ; the basioccipital is broad, unkeeled, and anteriorly is nearly plane, becoming strongly convex behind, where a deep depression is formed on each side between the condyle, tympanic and paroccipital process. The mastoid portion of the periotic, which is quite extensively exposed, lies in a deep fossa between the squamosal and exoccipital. Owing to the shallowness of the postorbital constriction, the frontals have less of the hour-glass shape than those of Hapalops, and much more prominent sagittal crest and temporal ridges ; the forehead is nearly plane longitudinally, slightly convex transversely, the sinuses not causing any external protuberances ; the anterior border has two shallow emarginations for the nasals, without distinct nasal processes. As compared with those of Hapalops, the nasals are short, very broad and moderately arched both longitudinally and transversely ; at the anterior end they are somewhat broadened and decurved to follow the maxillaries ; another and a very marked difference from the last named genus is to be seen in the anterior ends of the nasals, which are not deeply notched, but abruptly truncate and, consequently, have no lateral processes. The premaxillae (Plate LVI, fig. 2), are of the same general plan as those of Hapalops, but have nevertheless quite a different appearance ; they are very short and are lodged in so deep a notch of the bony palate that they project very little in front of the caniniform teeth ; the anterior branch is very short, rather slender, and contracts rapidly forward ; on the other hand, the poste'ro-external branch is very broad, much broader than in any known species of Hapalops and the spine is narrower, though quite heavy ; the incisive foramen is thus reduced to a narrow oval, considerably smaller than in Hapalops, but much larger than the narrow slit of Hyper- leptus. The maxillary is long and low, with short preorbital portion, which ends abruptly in the broad, rounded, pillar-like sheath of the caniniform tooth ; the preorbital fossa is very deep and has a well defined dorsal border ; the depth of these fossae, the great width of the muzzle in front of them, and the shortness of the premaxillaries give a highly char- acteristic appearance to this region of the skull ; dorsally, the facial por- tion of the maxillary is curved toward the median line, overlapping the 272 PATAGONIAN EXPEDITIONS : PALEONTOLOGY. edge of the nasals and forming a considerable part of the roof of the broad nasal chamber. The zygomatic process of the maxillary is rather short, but is given an appearance of prominence by the depth of the preorbital fossa ; the infraorbital foramen is small. The lachrymal is like that of Hapalops except that the foramen is narrower and more slit-like. The palatine processes of the maxillaries are remarkable for their great expan- sion in front of the molariform teeth and for the great depth of the V-shaped notch which lodges the premaxillae ; between the molariforms the palate is rugose, but only moderately convex. The palatines are short and together form a triangular plate, with sharp apex directed forward ; the posterior nares are very broad and their front border is behind the last tooth. The mandible (Plates LV, figs. \d, 2; LVI, 4, 4^) has a short, but ex- tremely thick and heavy horizontal ramus, with strongly convex ventral border ; the symphysis is short and steeply inclined and the chin is abrupt ; the predental beak is very short, deeply constricted at the base by a notch on each side for the upper caniniform, and of triangular shape, contracting to a point anteriorly ; as a rule, the dorsal surface is but moderately con- cave and the lateral borders are depressed and everted. In one specimen, however, which is apparently referable to this species (A. M. N. H., No. 9,575, Plate LVI, 3, 3*2) the beak has quite a different appearance; the notches for - are unusually large and deep and, seen from above, the beak is cordiform, rather than triangular, and is more concave, with mar- gins less everted. An apparently constant difference of the present species from E. ingens is in the mental foramina, of which a single conspicuous one is found on each side of the base of the beak. The coronoid process is higher and more erect, less inclined and recurved than in E. extermis, but the angular process is considerably shorter. MEASUREMENTS. Type. No. 9,24.1. No. 9,575. No. 15,314. Occiput, height .043 " width at base .058 Skull, width at postorbital constriction .038 " " over J- 042 Palate, width at 1 026 " " " L 016 Mandible, length from condyle 113 .115 .119 " angle .128 EDENTATA OF THE SANTA CRUZ BEDS. 273 MEASUREMENTS. Type. No. 9,241. No. 9,575. No. 15,314. Mandible, length of predental beak 021 .027 .026 " depth below ^ 030 .028 .030 " thickness below ff .016 .017 .017 " length condyle to ? 052 .052 .049 Except in a few details, the vertebrae (Plate LVII, fig. i) are very similar to those of Hapafaps. The atlas is broader in proportion to its length, a difference which is principally due to the larger size of the trans- verse processes ; the neural arch is narrower antero-posteriorly, not ex- tending over the posterior pair of cotyles and more distinctly emarginate between the anterior pair ; the latter are quite closely approximated and ventrally are separated only by a deep and narrow notch ; the inferior arch is slender and has a more prominent hypapophysis than in Hap- alops, while the transverse processes are longer and have a more reg- ularly curved free border. The neural spine of the axis is much larger than in the last named- genus, extending well over the atlas. In the other cervical vertebras the principal difference from Hapalops consists in the narrower neural arches and the larger neural spines and transverse pro- cesses. In the anterior thoracic region also the spines are longer and on the first and second vertebrae they are nearly erect. The posterior tho- racics, lumbars and sacrals are not known. Associated with the American Museum specimen (No. 9,241) are nine caudals from the anterior part of the tail and these are supplemented by an individual (No. 15,314) in the Princeton collection, which has a num- ber of the caudals, including a series of nine from the hinder part of the tail, lacking not more than two or three terminal vertebrae; the full number of caudals can therefore hardly have exceeded twenty or twenty- one. As a whole, the tail is much like that of Hapalops, of moderate length, but very heavy, rapidly tapering behind, while the individual vertebras are of the type common to all of the known Santa Cruz Gravi- grada; the centra diminish steadily in diameter, but very gradually in length as far as the tenth caudal ; from the latter backward the decrease in size is much more rapid and is accompanied by a marked depression or flattening in the hinder part of the tail ; the facets for the chevrons are very obscure, if present at all, on the first caudal, but each succeeding vertebra to the ? fifteenth has two prominent pairs of such facets, the 274 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. anterior pair separated from the posterior by transverse grooves. The neural arch is high on Cd. i and continually decreasing in size, becomes an open groove on ?i3; the spine is not distinguishable beyond 6 ; the zygapophyses, which are at first very conspicuous, diminish Part passu with the reduction of the neural arch, from ? 14 they are mere vestigial tubercles and they are absent on ?i8. The transverse processes are very long, broad and depressed on i, and, though rapidly reduced in length, they are still distinct on ?i8; on 2 and 3 these proc- esses have curious expansions of the distal end, are quite slender from 4 to 7, and from 8 to ?I3 again have well defined distal expansions. The chevrons are known only from the hinder part of the tail and three are present with the caudals of No. 15,314 ; these are very small canoe-shaped bones, with a deep vascular channel, which is almost closed dorsally by the lateral expansion of the facets for the vertebral centra; two of the chevrons have each two pairs of such facets, while the smallest of the three, which was apparently attached to the ? fourteenth caudal, has but a single pair. In the subjoined table the dimensions of caudals ?u, ? 13, ?i6 and ?i8 are from No. 15,314, all the other measurements from No. 9,241. MEASUREMENTS. Atlas, length 0315 Second thoracic, length of centrum. . . .018 " width 062 " " width of anterior face .017 " height 032 " " height 06 1 Axis, length of centrum (excluding First caudal, length of centrum 022 odontoid) 023 " " width of anterior face . . . .027 " width of anterior face 0305 " " over transverse pro- " " posterior face 017 cesses 109 " " neural spine (fore and " " height 037 aft) 036 Fifth caudal, length of centrum 022 Third cervical, length of centrum 018 " width of anterior face ... .0215 width of anterior face .. .015 " " " over transverse pro- Fifth cervical, length of centrum 018 cesses 063 " width of anterior face . . .014 " " height 033 Seventh cervical, length 017 Seventh caudal, length of centrum . . . .021 " width of anterior face .015 " " width of anterior face . .020 Neck, length in a straight line 144 " " over transverse First thoracic, length of centrum 019 processes 0565 width of anterior face . . .014 " height . .030 height (including neu- Ninth caudal, length of centrum 020 ral spine) 059 " " width of anterior face. . . .019 EDENTATA OF THE SANTA CRUZ BEDS. 275 . MEASUREMENTS. Ninth caudal, width over transverse pro- ? Sixteenth caudal, length of centrum. .0135 cesses 0425 " " width of anterior ? Eleventh caudal, length of centrum .. .0185 face oil " " width of anterior face .017 " " " over trans- " over transverse verse pro- processes 038 ccesses 016 " height 023 ? Eighteenth caudal, length of centrum .0105 ? Thirteenth caudal, length of centrum .016 width of anterior width of anterior face 009 face 014 " " " over trans- " over trans- verse pro- verse pro- cesses 0125 cesses 024 Of the fore-limb only the radius is known ; it resembles that of Hapa- lops, but is more slender in proportion to its length; the proximal facet for the ulna is remarkably small and is confined to the postero-external aspect of the head ; the surface for the humerus is transversely oval and has, in addition to the usual concavity, a narrow plane facet on the inner side ; the bicipital tubercle is very large ; the shaft is slender and antero-pos- teriorly compressed. The pes is represented by the second and third digits. These are more of the Analciiiiorplius than of the Hapalops type. Metatarsal II is more elongate and slender than in the latter and the proximal end overlaps the head of metatarsallll more extensively, but has no facet for the ectocunei- form ; the distal trochlea is more asymmetrical than in Hapalops, the great carina being displaced more toward the fibular border and projecting less on the dorsal, more on the plantar side ; on the dorsal side of the shaft, above the distal trochlea, is a large fossa not indicated in Hapalops. Metatarsal III, though short and stout, is conspicuously longer and more slender than in the last named genus, and the proportions of these two metatarsals suggest that IV and V also were less abruptly different from III than in the latter. In digit II the proximal phalanx is long and narrow, very thick planto- dorsally ; in digit III this phalanx is of nearly the same length and, though broader and far thicker than in II, is proportionately much less massive than in Hapalops. The second phalanx is very long and quite slender and in III is more elongate and less heavy than in the last named genus. The unguals also differ in shape from those of the latter, being more decurved, 276 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. with wider and more regularly arched, less sloping dorsal border, and the cleft at the distal end is almost obsolete. MEASUREMENTS. Radius, length 155 Second phalanx, digit II, prox. width. .012 " width of proximal end 0235 " " " " " thick- " thickness of proximal end ... .018 ness. .017 width of distal end 0285 " " " distal thick- Metatarsal II, length 029 ness. .01 1 " width of proximal end . .016 Second phalanx, digit III, length 023 " " distal end 0135 " " " " prox. width .015 Metatarsal III, length 0265 " " thick- " " width of proximal end . .019 ness. .021 " "distalend 017 " distalthick- First phalanx, digit II, length 013 ness 015 " " proximal width .014 ' Ungual, digit II, length 048 " " thick- " " " proximal width 0105 ness. .019 " ' thickness.. .016 First phalanx, digit III, length 017 Ungual, digit IV, length 044 " " " " proximal width .016 " " " proximal width 012 " thick- ' " thickness . .016 ness. .0215 Digit II, length 095 Second phalanx, digit II, length 025 EUCHOLCEOPS CURTUS Ameghino. Eucholcaops curtus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 154. For the present, at least, it is desirable to keep this species distinct, for the type and only known specimen is a very curious skull, remarkable for its shortness and great breadth. To a certain extent, this shortness is more apparent than real, for the skull has been " telescoped " by a longi- tudinal compression, but even after making due allowance for this, the proportions remain very unusual. The dentition does not differ from that of E. fronto, more than the teeth of various individuals of the latter differ from one another, and the peculiarities of the skull are best indicated in the measurements. MEASUREMENTS. Upper dentition, length 056 -2-, length 0045 1-A 028 " width 009 *, length (i.e., antero-posterior diameter) .009 •&, length 005 " width (i. e., transverse diameter) 008 " width 009 EDENTATA OF THE SANTA CRUZ BEDS. 277 MEASUREMENTS. -4-, length 005 " width 008 £, length 003 " width 0075 Skull, length in median basal line 094 " " condyles to anterior nares .117 •' width at postorbital con- striction 034 Cranium, length occipital crest to rim of orbit 083 Face, length orbit to anterior nares . . . .034 Occiput, width 058 Face, width over 1 046 Palate, length in median line 046 " width at 1 026 " « << & 013 FIG. 33. Eucholceops curtus, type ; x \. Ameghino Collection. FIG. 34. Eucholoeops curtus, type ; x \. Ameghino Collection. 278 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. MEGALONYCHOTHERIUM gen. nov. (Plate XLVI.) This genus is represented by a single skull, without mandible (No. 15,593) fr°m which unfortunately, all the teeth are missing, except the basal portion of ^ on the right side. In general character the skull is much like that of Hafialops, but the resemblance to Megalonyx is so much more striking than in the case of any other known Santa Cruz fossil, that it seems advisable to separate it generically from the former. The dentition has a very suggestive resemblance to that of Megalonyx, as is evident from the empty alveoli ; - is much larger than in Hapalops and of an entirely different shape, obviously resembling the same tooth in Megalonyx, being laterally compressed and antero-posteriorly elongate, but is more trihedral and less oval than in the Pleistocene genus, with the anterior surface a rounded edge and the posterior relatively broad ; the tooth is placed as far forward as possible in the maxillary, which has no plate-like extension in front of it, such as occurs in Hapalops, and no such rounded, pillar-like expansion as is found in Eucholceofis, for it does not project outside of the line of the other teeth, as it does in the latter. The first molariform tooth, a, which is separated by a considerable dia- stema from -, is similar in form to that of Megalonyx, but relatively larger ; ^ and - are of nearly equal size and resemble those of the Pleis- tocene genus, while A is proportionately smaller than in the latter. In the skull also there is a suggestive resemblance to Megalonyx, with many differences in matters of detail. In general proportions the follow- ing differences from Megalonyx jeffersoni may be noted : The cranium is relatively shorter and the face longer, but, at the same time, the diastema is shorter ; these differences are largely due to a shifting of the orbits in the Pleistocene species, in which the front rim of the orbit is well in advance of 2-, making the preorbital region extremely short, while in the Santa Cruz genus the edge of the orbit is over the space between - and ^ ; the whole skull, especially the facial region, is much shallower dorso- ventrally ; the postorbital constriction is shallower and more anterior in position, while the preorbital fossae are much more distinctly defined ; the zygomatic process of the squamosal is more slender and much more horizontal in direction. The sagittal and occipital crests are quite promi- nent, the former more so than in any other known genus of the Santa Cruz Gravigrada, and the muzzle is broad and abruptly truncate. EDENTATA OF THE SANTA CRUZ BEDS. 279 In the entire absence of the skeleton, it is impossible to speak with confidence regarding the relationships of this genus, but, so far as can be judged from the dentition and skull, there is no apparent reason why it may not have been the direct ancestor of Megalonyx ; on the other hand, it was clearly derived from the same stock as Hapalops. MEGALONYCHOTHERIUM ATAVUS sp. nov. (Plate XLVI.) This species, the type of which (No. 15,593) was found by Mr. Peterson on the coast of Patagonia, about five miles south of Coy Inlet, is of moderate size, about equal in this respect to Hapalops brachycephahts. The dentition has been sufficiently described in the generic diagnosis and it only remains to notice that the two series of upper teeth are nearly parallel and to give the dimensions. MEASUREMENTS. Upper dentition, length 06 1 -§-, length 007 " 1--5- 033 " width 012 1, length (i. e., antero-posterior diame- A, length 0085 ter) 01 1 " width oil " width (i. e., transverse diameter) . . . .007 •§-, length 007 ^, length 0085 " width 008 " width on As the most significant fact concerning this animal is its probable ances- tral relationship to Megalonyx, it will be well to make a detailed compari- son of the skull with that of M. jeffersoni. The occiput of the Santa Cruz species, though of similar semicircular form, is relatively somewhat wider and lower, and the foramen magnum is larger, though of the same almost circular outline ; the median vertical ridge on the occiput is much wider, more rounded and less prominent, and the occipital crest is more distinctly defined and much narrower, not forming such a broad, rugose surface ; the condyles are missing and the paroccipital processes, though inconspicuous, are larger than in the Pleistocene' species. All of the ele- ments forming the cranio-facial axis are indistinguishably fused together ; this axis is relatively longer and narrower than in Megalonyx ; the basi- occipital is similar in the two species, with convex median portion and on each side a fossa into which open the condylar foramen and foramen lacerum posterius. The mastoid portion of the periotic is quite exten- 280 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. sively exposed on the surface of the occiput between the exoccipital and squamosal and forms a prominent ridge with a deep and narrow fossa on each side of it ; in the outer one of these fossae is a large venous foramen ; ventrally the periotic ends in a large, subcylindrical mastoid process, with a cup-shaped surface for the stylo-hyal. The parietals are large and form nearly the whole cerebral roof, with prominent sagittal crest extending along their entire length. The squamosal is also large and extends to the occipital surface, making up nearly half of the occipital crest ; ventrally this crest ends in a prominent tubercle, which is smaller than in M. jeffer- soni and nearer to the mastoid process ; the zygomatic process is much like that of Hapahps and pursues a horizontal course, not curving down- ward, nor diverging so far from the side of the skull as in Megalonyx ; another difference from the latter is that the dorsal border of the zygoma does not become continuous with the occipital crest. The temporal ridges of the frontals are much less prominent than in the Pleistocene species and the postorbital processes seem to have been insignificant ; the frontal sinuses are much less prominent and the fore- head is but moderately convex. The lachrymal resembles that of the other Santa Cruz Gravigrada and is far more prominent than in Mega- lonyx. The nasals are short, unusually broad, moderately curved longi- tudinally and almost plane transversely. The anterior nares are quite large and considerably higher than they are wide ; in shape they are much as in the Pleistocene species, but are covered more by the nasals and less by the maxillaries. The premaxillae have been lost, but from the facets on the maxillaries and the smaller, more V-shaped notch of the anterior border of the palate, it may be inferred that they were longer and more slender than in Mega- lonyx. The maxillary is longer than in the latter, especially the preorbital portion, with much better defined preorbital fossa and far more prominent zygomatic process ; the hard palate is very rugose and is perforated by many venous foramina, but the region between the molariform teeth is less convex than in many Santa Cruz species and conspicuously less so than in M. jeffersoni. The posterior nares have a shape similar to that of the latter, but differ in the wide separation, dorsally, of the pterygoids, which, in the Pleistocene species, meet in the median line and conceal the presphenoid and part of the basisphenoid. Part of the vomer is visible, descending gradually forward into the nasal chamber. EDENTATA OF THE SANTA CRUZ BEDS. 28 1 MEASUREMENTS. Skull, length in median basal line 136 Distance, condyle to glenoid cavity 027 Cranium, length occipital crest to edge " " "6- 071 of orbit 100 Rostrum, width 038 Face, length from orbit to anterior nares .036 Anterior nares, width 024 Occiput, height 040 Palate, length in median line 056 " width at base 055 " width at 1 024 Cranium, width at postorbital constriction .031 " " " 2- 013 " " over lachrymals 048 " " " & 012 Zygomatic arch, length 082 We may next consider a group of three genera, Schismotherium, Pele- cyodon and Analcimorphus, which are in some important respects more primitive than any of the genera described in the preceding pages ; they agree with one another in certain characters which, at first sight, seem to be very trivial, but are so remarkably constant that they must be regarded as significant. The first upper, or caniniform, tooth is implanted at a greater or less distance behind the anterior edge of the palate, and the second upper tooth, which in all other known Santa Cruz Gravigrada is transversely oval or rectangular, is, without exception, subcylindrical or styliform. The digits of the pes are more uniform in length than in Hapalops. ANALCIMORPHUS Ameghino. (Plates XLVII-XLIX.) Analcimorphtis Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 320. Ameghino has referred this genus to the Planopsidce (Prepotheriidce Amegh.), a reference which was justified by the similarities of the denti- tion, but the discovery of a large part of the skeleton shows that this genus is an undoubted member of the Megalonyc hides and, in particular, is nearly allied to Schismotherium and Pelecyodon. The type-species, A. inversus, is still very imperfectly known and it remains to be proved whether the second and very much larger species, A. giganteus, is or is not properly referable to the same genus. So far, however, as the known material permits of a decision, there is no reason to separate the two species generically. AnalcimorpJms is characterized primarily by the dentition, which has certain marked resemblances to that of the Planopsidce. In the upper jaw - is small, cylindrical, horizontally abraded and inserted far behind 282 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. the anterior margin of the palate and separated from - by a shorter, yet considerable, diastema ; - is subcylindrical, the antero-posterior diameter equalling or exceeding the transverse ; - and A are transversely oval, very broad, much compressed antero-posteriorly and of nearly equal size ; - is similar, but smaller. Of the mandibular dentition, T is caniniform, small, subcylindrical, horizontally worn and separated from 2 by a somewhat shorter diastema than that of the upper jaw; 2 and -3- are transversely oval or rectangular, broad, but less antero-posteriorly compressed than ^ and A, while T is again cylindrical. As the skull and skeleton are known only in A. giganteus, they will be described in connection with that species. ANALCIMORPHUS INVERSUS Ameghino. Analcimorphus inversus Amegh. ; Rev. Argent, de Hist. Nat-, T. I, 1891, p. 320. The type and only specimen of this species consists of a fragment of the right half of the palate with the second, third and fourth teeth in place, and the right ramus mandibuli, lacking the predental beak and the an- gular process, but retaining all of the teeth. That the animal was very young is shown by the open palatal suture, but its small size is not en- tirely due to youth and it could never have approximated the large species in stature. Except in regard to size, the dentition displays little that is specifi- cally characteristic; - tends to assume a trihedral form, with the apex turned forward ; ^ and - are very much compressed antero-posteriorly, while ^ and -3- are less compressed and more rectangular and T is very regularly cylindrical. The ventral border of the jaw is but moderately convex, and though the immaturity of the animal may partially explain this, the great differ- ence in the form of the mandible between this species and A. giganteus cannot be entirely accounted for in this manner. The postero-external opening of the dental canal is double, but, as may be inferred from the analogy of Hapafaps, this is doubtless individual. MEASUREMENTS. &-, length (i. e., antero-posterior diam- -8-, length .006 eter) 007 " width oio £, width (i. e., transverse diameter) . . . .006 A, length 0055 EDENTATA OF THE SANTA CRUZ BEDS. 283 MEASUREMENTS. A, width oio 3, length 005 Lower dentition, length 03 1 " width 006 " j_f . . .0205 i, length . . .007 T, length 003 " width 0065 T, width , 0025 Mandible, depth below 5 019 j, length 0045 " length condyle to T 068 " width 0065 ANALCIMORPHUS GIGANTEUS Ameghino. (Plates XLVII-XLIX.) Analcimorphus giganteus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 165. In addition to the type in the Ameghino collection, this species is rep- resented in the Princeton Museum by two individuals, one of which (No. 15,163, Plate XLVII) is a fine skull, lacking most of the occiput and the mandible, and the other (No. 15,561, Plates XLVIII, XLIX) consists of the skull, without mandible, four cervical, twelve thoracic, four lumbar and three caudal vertebrae, the sacrum, pelvis, hind-limb and pes almost complete. Both specimens were found by Mr. Peterson near Corriken Aike. At- first sight, the two skulls appear to be quite different in their proportions, so much so that I was inclined to separate them specifically and have, on p. 174, labelled the figure of the pes as A. leptoceplialns, but the difference is at least partially due to the fact that the isolated skull, which was imbedded in a soft matrix, is free from distortion, while the other, which was in a very hard concretion, has been laterally compressed and thus seems to be unduly narrow. The most obvious distinction of this species from the preceding one is its very much larger size, but there are additional differences in the teeth. Of the upper series - is the smallest and the portion protruded from the alveolus is very small, both in height and in diameter ; it is of irregularly oval section and recurved ; the grinding surface is inclined ; the tooth is inserted well behind the anterior border of the palate and is followed by a considerable diastema ; - is styliform, of oval or irregularly quadrate section, and has an inclined masticating surface, with high anterior and very low posterior crest, enclosing a rounded, shallow depression ; - and all the succeeding teeth are isolated by considerable interspaces ; 3-, the largest of the series, is transverse and either oval or pyriform in shape ; 284 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. the anterior crest is curved and terminates internally and externally in elevated points, concealing the valley in side-view ; - resembles 3-, but is smaller and more constantly oval and - is quite small. The teeth are somewhat oblique to the median line of the palate and the two series are nearly parallel. In the mandibular dentition, which is known only from the type, T is very small, cylindrical, horizontally abraded, and separated from -2- by quite a long diastema ; -2- and ^ are transversely oval, more compressed antero- posteriorly and less rectangular than in A. inversus, and T is less cylindrical than in the latter and more obliquely elliptical. MEASUREMENTS. Type. No. 15,561. No. 15,163. Upper dentition, length .0605 .0545 << " " 2.-0. 041 .042 .037 " " " 3.-A 030 .030 .027 -L, length (i. e., antero-posterior diameter) .006 -0055 " width (i. e., transverse diameter) .005 .005 3., length 008 .0085 .008 " width 008 .008 .008 »-, length 008 .007 .008 " width 013 .0145 .014 A length 0075 .007 .007 " width 012 .0125 .012 4, length 006 .007 .007 "width 0095 .0115 .0115 The dimensions of the lower teeth are all taken from the type. Lower dentition, length 052 ^, width 013 " j_¥ 034 3, length .007 T, length 005 " width 012 " width 005 T, length .on j, length 0075 " width oio Skull (Plates XLVII, XLVIII).- -The general appearance is quite like that of the larger species of Hapalops, but with many minor differences. The occiput is relatively high and from its summit to the parietal emi- nence the rise is slight and from the eminence to the coronal suture, the lowest point of the cranium, is a slight descent ; from the coronal suture is an almost imperceptible rise to the interorbital region and thence a very gentle descent to the muzzle, which is quite high dorso-ventrally. The EDENTATA OF THE SANTA CRUZ BEDS. 285 cranium is of nearly uniform width, the cerebral expansion and the post- orbital constriction being moderate and the broadening of the forehead slight ; the preorbital fossae are shallow and the broad rostrum has nearly parallel sides. The basioccipital is short and wide, nearly flat and without keel, and deeply emarginated by the foramen magnum ; the condylar foramen is very large and conspicuous, while the foramen lacerum posterius is still larger and is chiefly, if not entirely, enclosed in the basioccipital ; the foramen magnum is low and wide, of transversely oval shape and with dorsal margin so prominent as to give it something of a tubular form ; the paroccipital processes are small but distinct; the condyles are rela- tively larger than in most other contemporary species and are not so sessile ; they project freely behind the plane of the occiput and form the hindermost part of the skull ; the ventral notch between the condyles is unusually deep, much as in Megalonyx. As a whole, the occiput is high, inclined decidedly forward, bringing the summit on a line with the audi- tory meatus ; it is strongly convex transversely, with median prominence for the vermis ; the inclination of the occiput is more decided than in most of the Santa Cruz Gravigrada, exposing the condyles when the skull is seen from above ; the occipital crest is very distinct, though not very prominent, and dorsally curves forward between the parietals, clearly demarcating them from the supraoccipital. The mastoid portion of the periotic is narrow and rugged and ends ventrally in a short, cylindrical process for the attachment of the stylohyal. The tympanic is, as usual, a mere bony ring, with large and irregular auditory meatus. The basi- sphenoid is long and broad, lying at a lower level than most of the basi- occipital, which descends to meet it ; the presphenoid is concealed by an expansion of the vomer, of which the anterior visible portion is a thin, vertical plate with ventral border descending forward, while the hinder part is a horizontal plate covering much of the presphenoid ; except for a large descending process, the alisphenoid is quite small, but the orbito- sphenoid is relatively large. The parietals are large in both dimensions ; for most of its length the sagittal crest is feebly indicated, becoming more distinct anteriorly; the vascular foramina along the parieto-squamosal suture are few. The squamosal is long and low and forms but little of the occipital crest, and develops a prominent tubercle at the postero-inferior angle; the post- 286 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. tympanic process is very small, and the zygomatic process is short and nearly straight, with a slight downward curvature ; the jugal, which is missing, must have been unusually long. The lachrymal, which is of the ordinary type, appears to be less prominent than in many other species, on account of the breadth of the rostrum; in No. 15,163 the foramen is con- siderably smaller than in the other skull, but the difference is probably individual. The frontals have less of the hour-glass shape than usual, owing to the shallowness of the postorbital constriction ; large sinuses are indicated by the convexity of the forehead ; the sagittal crest is quite distinct and bifurcates into well defined temporal ridges ; the spine which overhangs the optic foramen is continued as a short ridge along the suture with the orbito-sphenoid. The nasals are long and each one is convex transversely, producing a groove along the median line ; they are nar- rowest at the hinder end, broadening gradually to the anterior end, which projects freely beyond the maxillaries ; the lateral notches are shallower than \n-Hapalops and the lateral processes present outward instead of dorsally, very much as in Mylodon. The premaxilla:; are missing, but the facets for them indicate that they were of the type common to the Megalonychidce, with certain peculiarities ; the facet for the postero-external branch is a high, narrow concavity, which rises unusually far upon the sides of the anterior nares ; a second and much smaller facet for the same branch is upon the lateral aspect of the palatine process, while the median notch for the spines is not unlike that of Hapalops, but somewhat smaller. The preorbital portion of the max- illary is large and the fossa is of variable depth ; the zygomatic process is not very prominent, but is broad antero-posteriorly and is perforated by a relatively small infraorbital foramen. The hard palate is of the type usual in the family, but is wider than in most of the genera and, owing to the irregular sizes of the teeth, its width varies more in the different parts ; the posterior convexity is moderate and extends only to the space between ~ and - and in front of this the palate is flat, or slightly concave. A distinct difference between the two specimens is in the shape of the posterior narial opening; in No. 15,163 the front part of this opening is narrow, with a median spine, and extends nearly to the anterior face of --, while in 15,561, it ends behind A, has no spine and is broader. The pterygoids are not entirely covered by the descending plates of the ali- sphenoids ; in one of the skulls (No. 15,163) at the base of each pterygoid, EDENTATA OF THE SANTA CRUZ BEDS. 287 just external to its junction with the basisphenoid, is a broad, conspicuous groove, leading obliquely into the narial canal. The mandible, known only in the type, can be but partially described, because at the time of my visit to La Plata, the jaw was still partly in the matrix, and the ascending rami and the predental beak are broken. The symphysis is very long, extending back nearly as far as ^, and the beak was evidently long, perhaps very elongate, and is but moder- ately concave on the dorsal side ; the ventral border of the horizontal ramus is strongly convex, greatly increasing the depth of the jaw, which below ^ is 47 mm.; the shape resembles the jaw of Megatherium and is quite unlike that of A. inversus, in which the ventral border is almost straight. The stylo-hyal (Plate XLVII, Fig. i) agrees in its general form with that of the modern sloths and of the Pleistocene Gravigrada ; it is hammer- shaped, with proximal end expanded antero-posteriorly and compressed laterally ; the surface for the periotic is anterior and forms a small tubercle ; the slender shaft is subcylindrical, with a sigmoid curvature. MEASUREMENTS. No. 15,561. No. 15,163. Skull, length in median basal line 144 .141 " " condyles to anterior nares ?. 168 .171 Cranium, length condyle to edge of orbit 132 .130 Face, length orbit to anterior nares ?-O37 .043 • Occiput, height .042 " width at base 059 .060 Skull, width at postorbital constriction 041 .046 Rostrum, width .037 .041 Zygomatic arch, length 100 .096 Palate, length in median line 072 .059 " width at 1 02 1 .024 " " "2- 017 .018 " " " & 016 .014 Vertebral Column (Plate XLIX, figs, i, 2, 3*). --The atlas is longer than in Hapalops longiceps, with wider neural arch and even more reduced neural spine ; the anterior cotyles are farther apart ventrally ; the transverse process is more horizontal, less extended antero-posteriorly, not reaching to the anterior cotyle, which projects in front of it, and is separated from the posterior cotyle by a deep notch ; on the ventral side 288 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. of the process, near the posterior border, a prominent, rib-like elevation runs obliquely outward and backward from the side of the inferior arch to the posterior angle of the process, where it ends in a rounded tubercle. The axis is relatively longer and narrower than in Hapalops longiceps and has a prominent ventral keel ; the anterior cotyles rise higher upon the sides of the neural canal, which is higher and narrower and more circu- lar; the spine is a large, hatchet-shaped plate, which differs from that of Hapalops in the upward slope of the much thickened posterior border ; the transverse process is long and slender and the vertebrarterial canal is shorter than in Hapalops. The third and fourth cervicals differ little from those of the latter genus, except that the spine, which is considerably higher on 3 than on 4, is higher and more pointed. The twelve thoracic vertebrae associated with No. 15,561 are from dif- ferent parts of the region. The anterior thoracics have small centra, which are somewhat contracted in the middle ; the neural spines are longer and more slender than those of Hapalops longiceps and have a stronger back- ward inclination, while the tips are more thickened and rugose. In the hinder part of the region the vertebras have short and massive centra, which in the last two have a median keel and a pair of very small ventral foramina ; the neural spines are shorter and much narrower than in H. longiceps, but with much heavier tip; the spine of the last thoracic is much broader than that of the penultimate one ; transverse processes are prominent on all and even the last one appears to have a facet for the tubercle of the rib ; metapophyses are first distinguishable on the antepe- nultimate vertebra, suddenly becoming very prominent on the penultimate. Accessory zygapophyses are present only on the last vertebrae, or, per- haps, on the last two. Four lumbar vertebrae are present ; they have centra of nearly uniform length, becoming broader and more depressed posteriorly ; all have the ventral keel and foramina, but the latter are conspicuous only on the third and fourth, and largest on the third ; the neural spines are lower, broader and more erect than those of the posterior thoracic region and are shorter than the lumbar spines of Hapalops longiceps ; the transverse processes are shorter and less antroverted than in the latter species, and the acces- sory zygapophyses are like those common to all the family. The sacrum consists of five vertebrae, of which the first is less com- pletely incorporated than the others and seems to belong to the lumbar EDENTATA OF THE SANTA CRUZ BEDS. 289 series ; the centrum of this vertebra is not coosified with the second, though it probably became so in the fully adult animal, and the neural spine is also free, but the posterior pair of zygapophyses are fused with the anterior pair of the succeeding vertebra and the transverse processes, which are of lumbar type, though much longer than in any of the preced- ing vertebrae, are fused with the ilia ; the absence of pleurapophyses further distinguishes this vertebra from the first true sacral. The four succeeding vertebras are thoroughly coossified, their spines forming a ridge which is notably lower than in H. longiceps ; the first two are ankylosed with the ilia and the fourth with the ischia. The first three caudal vertebrae are quite like those of H, longiceps, but have somewhat smaller and more depressed centra and less developed spines ; the spine is obsolete on the third caudal. MEASUREMENTS. Atlas, length 037 " width 063 Axis, length of centrum 030 " width of anterior face 034 " height of neural spine 046 Third cervical, length of centrum 021 " width of anterior face. . . .016 " over prezygapoph- yses 029 Fourth cervical, length of centrum 020 width of anterior face. .015 Anterior thoracic, length of centrum . . . .02 1 width of anterior face .02 1 " over transverse processes 052 height of neural spine .042 width of spine at base .021 " " " " tip . .018 Last thoracic, length of centrum 026 width of anterior face 032 height of neural spine. . . .052 First lumbar, length of centrum 026 width of anterior face 034 Second lumbar, length of centrum 027 " width of anterior face .. .034 Second lumbar, width over transverse processes 057 " " height of neural spine .. .067 " " width of spine at base .. .027 " " " " " "tip ... .026 Third lumbar, length of centrum 029 " " width of anterior face . . . .036 Fourth lumbar, length of centrum 027 " " width of anterior face .. .037 Sacrum, length 177 " width of anterior face 041 " " " posterior face 036 First caudal, length of centrum 022 " " width of anterior face 032 " " over transverse pro- cesses 103 Second caudal, length of centrum 022 " " width of anterior face. . .031 " over transverse processes 082 Third caudal, length of centrum 022 " " width of anterior face 027 " " over transverse pro- cesses 065 ? Fourth chevron, dorso-ventral height. .025 Pelvis. — The pelvis differs in several respects from that of Hapahps ; the ilium has a longer and better defined peduncle and, consequently, a 290 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. larger sacro-sciatic foramen, while the anterior expansion is more gradual. The dorsal branch of the ischium is very short and depressed, broadening abruptly behind the acetabulum, thus making the peduncle extremely short, and the tuberosity is quite prominent ; the ventral portion of the ischium is relatively much longer than in Hapahps, so that the principal diameter of the obturator foramen is dorso-ventral, instead of antero- posterior. The pubis is a slender rod, which is considerably longer and less oblique than in Hapahps, and the symphysis, which is formed by both pubes and ischia, is quite elongate. Owing to the length of the pubes and ischia the pelvic opening has a different shape from that of the last named genus, the dorso-ventral diameter exceeding the transverse. MEASUREMENTS. Pelvis, length 283 Obturator foramen, dorso-ventral di- Ilium, length 184 ameter 073 Ischium, length 109 Pelvic opening, dorso-ventral diameter. .117 Acetabulum, antero-posterior diameter .051 " " transverse diameter... .095 " dorso-ventral diameter . . .039 Sacro-sciatic foramen, length 06 1 Obturator foramen, antero-posterior di- ameter 055 Hind-Limb. — The bones of the hind-leg differ considerably from those of Hapahps. The femur (Plate XLIX, fig. 3), which has been consider- ably distorted by pressure, is of nearly the same length as in H. longiceps, but is notably more slender and less flattened ; the large, hemispherical head rises well above the level of the great trochanter and presents more proximally, less directly inward ; the sulcus for the round ligament is a deep pit of elongate, narrow oval shape ; the great trochanter is heavy, but not prominent and the digital fossa is almost obsolete, while the third trochanter is distinctly smaller than" in H. longiceps. The shaft is more rounded and slender than in any other of the Santa Cruz Gravigrada, except Schismotherium. The rotular groove is short and narrow. The tibia (Plate XLIX, figs. 4, 4^) has a much more massive cnemial process than that of H. longiceps, and the shaft is more slender, more compressed antero-posteriorly and broadens less distally. A noteworthy difference from all the known contemporary Gravigrada consists in the absence of the prominent process, with its deep tendinal sulcus, from the inner side of the distal end, and the internal malleolus is quite obsolete ; the astragalar surface is narrower, but deeper planto-dorsally than in EDENTATA OF THE SANTA CRUZ BEDS. 29 1 Hapalops ; the intercondylar ridge is more prominent and the internal facet less concave. The fibula resembles that of H. longiceps, but has a more trihedral and more uniform shaft, which is less thickened proximally and narrower dis- tally ; the distal end is extremely massive. MEASUREMENTS. Femur, length from head 218 Tibia, width of shaft in middle 024 " " " great trochanter. .215 " thickness of shaft in middle 018 " width of proximal end 065 " width of distal end 043 " " distal end over tuber- " thickness of distal end 029 osities .074 Fibula, length 144 ' " " con- " width of proximal end 020 dyles .063 " thickness of proximal end 023 " " rotular groove 035 " width of shaft in 'middle oil Tibia, length 160 " thickness of shaft in middle. . .01 1 " width of proximal end 066 " width of distal end 025 " thickness of proximal end 057 " thickness of distal end 025 The pes (Plate XLIX, fig. 5) departs in some noteworthy respects from that of Hapalops. The astragalus is slightly longer and narrower than that of H. longiceps ; the trochlea is less grooved and the inner condyle less prominent, while the outer one is more so ; the sulcus which invades the trochlea from the distal end is broader and much more extended dorsally ; the external calcaneal facet is somewhat smaller and less con- cave, while the inner one is larger and separated from the former by a broader sulcus; the neck is longer and more oblique, inclining much more strongly toward the tibial side ; the head is narrower transversely and thicker planto-dorsally. Unfortunately, the calcaneum is so broken that little can be determined with regard to it; it is plain, however, that the proximal expansion of the tuberosity is much more gradual than in Hapalops and that the two astragalar facets are much more widely separated. The navicular is very like that of Hapalops, but is even shorter proximo-distally and its outer sur- face for the astragalus more convex. The entocuneiform is long, narrow and scale-like ; the proximal end is the widest part and bears an oblique, concave facet for the navicular; at the distal end it becomes narrower and much thicker and articulates extensively with metatarsals I and II. The mesocuneiform is even shorter, but broader and thicker than in Hapalops. The ectocuneiform is also shorter and has a relatively narrower 292 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. navicular facet. The cuboid is smaller than in H. longiceps and has a smaller surface for the astragalus ; the calcaneal facet is oblique and con- vex; the distal end is divided into a larger facet for the fifth metatarsal, and a smaller one for the fourth (a very unusual arrangement), the two separated by a distinct groove. A large plantar sesamoid is present. The most peculiar part of the hind-foot and that which differs most from Hapalops, is the metatarsus, which, as in all other known contemporary Gravigrada, consists of five members. Metatarsal I is much stouter than in H. longiceps ; it is considerably longer on the plantar than on the dorsal side, where it is cut away by the long, sloping facet for the ento- cuneiform ; the shaft is short, broad and thick, and the distal trochlea has an unusually prominent carina, which is greatly extended planto-dorsally. Metatarsal II, though short and stout, is somewhat longer and more slender than in H. longiceps ; the proximal end is broader, overlapping I and III more extensively ; the distal end is remarkable for the immense carina, which projects far in front of and behind the shaft. Metatarsal III is the heaviest and, except I, the shortest of the series ; the proximal end is somewhat broader than in the last named species and the extremely short shaft is much more constricted below this proximal expansion, broadening again almost immediately to form the distal end ; the carina has an even more exaggerated development than that of II. Metatarsal IV is heavier and much shorter than in Hapalops, not greatly exceeding II in length, and diverges less from III toward the fibular side ; the proximal end has a less oblique and much narrower facet for the cuboid ; the shaft is longer and more slender than in any of the pre- ceding metatarsals and the distal carina, though very large, is less prom- inent than in II or III. Metatarsal V is considerably damaged, but is obviously shorter and heavier than in Hapalops ; the proximal end has a broader cuboid facet, but, apparently, no such great wing-like process from the fibular side as characterizes Hapalops, Megalonyx and Nothrotherium, while the distal trochlea is much better developed and has a more prominent carina. Comparing the pes of the present species with that -of Hapalops, H. longiceps for example, one is immediately struck by the fact that in the former the foot is more isodactyl, there being no such great difference in the length of the various metatarsals as in the latter, and, owing to the arrangement of the tarsal bones, all five of the metatarsals have their EDENTATA OF THE SANTA CRUZ BEDS. 293 distal ends on nearly the same transverse line. This gives to the whole foot a distinctly different appearance, since there is no such marked con- trast in length and thickness between II and III, on the one hand, and IV and V, on the other. The phalanges are preserved only in connection with the three external digits and of these only IV has the ungual. The proximal phalanx is shaped much as in H. longiceps, but the median groove of the distal trochlea is far deeper; this phalanx is heaviest in digit III and very small in V. The second phalanx of digit III is very heavy, much longer than in the last named species and has a much more extensive and more deeply grooved distal trochlea, which describes more than a semicircle and projects freely in front of and behind the shaft ; in digit IV this phalanx is longer and much more slender, while in digit V it is of similar shape, but very much smaller, the first and second phalanges together being hardly longer than the proximal one alone of digit IV. Unfortunately, the only ungual phalanx preserved, that of digit IV, is not represented in the type of H. longiceps ; however, in the latter the ungual of digit II is present and it may be assumed that that of IV was not very different. In A. giganteus the ungual of IV is considerably longer than the ungual of the second digit in the last named species, and especially the portion distal to the subungual process is more slender and laterally compressed, more decurved and sharply pointed; the subungual process is not so prominent, but longer proximo-distally, extending to the edge of the trochlea. MEASUREMENTS. Astragalus, length 044 Metatarsal II, length 037 " width of trochlea 028 " " proximal width 019 " " distal end 023 " least width of shaft. . . .012 Calcaneum, width at constriction OI95 " distal width 015 Navicular, length on tibial side 014 Metatarsal III, length 029 " " " fibular side 004 " " proximal width 024 width 026 " " least width of shaft .. .017 " thickness 029 " distal width 0085 Metatarsus, width of proximal end . . .068 Metatarsal IV, length 034 Digit IV, length 125 " " proximal width 014 Metatarsal I, length 022 " " " thickness. . . .020 " " proximal width 008 " least width of shaft. . . .on " " thickness 019 " distal width 0135 " distal width 009 Metatarsal V, length 034 " " thickness 018 " " proximal width ?.oi6 294 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. MEASUREMENTS. Metatarsal V, proximal thickness ... .019 First phalanx, digit III, length 020 " " prox. width . .016 thick- ness . .024 " distal thick- ness. .019 First phalanx, digit IV, length 016 " " prox. width.. .013 " distal width .. .oil thick- ness . .014 First phalanx, digit V, length oil " " " " prox. width.. .009 " " " thick- ness . .015 " " " " distal thickness .007 Second phalanx, digit III, length . . . .030 " " prox. width .015 Second phalanx, digit III, prox. thick- ness . .019 " distal thick- ness . .020 Second phalanx, digit IV, length . . . .03 1 " " " prox. width .012 " thick- ness . .019 " " " " distal thick- ness . .0165 Second phalanx, digit V, length 018 " " prox. width .008 " " " thick- ness . .013 " " distal thick- ness . .008 Ungual, digit IV, length 06 1 " " " proximal width 013 " " " " thickness . .021 Relationships. — As remarked above, it is a matter of some uncertainty whether the two species referred to Analcimorphus really belong to the same genus ; probably they do and almost certainly they are very closely allied, if not congeneric. In what follows, however, attention will be con- fined to A. giganteus, because of the relatively full information concern- ing that species which we possess. The entire structure of the skeleton shows that the present species is a member of the Megalonychidce and, in particular, that it is nearly connected with Schismotherium and Pelecyodon. At the same time, there are many points of resemblance to the Planopsidce, to which group Ameghino has referred the genus ; the dentition, several characteristic features of the skull and the proportions of the pelvis pre- sent the most obvious of these approximations to the Planopsidce. To a certain extent, therefore, the present genus is a connecting link between the two families, although it cannot itself be placed in the line of descent, because it is contemporaneous with the differentiated Planopsidce; it should, on the contrary, be regarded as a derivative of the common an- cestor of both families and so little removed from that ancestor as to indi- cate its probable character. EDENTATA OF THE SANTA CRUZ BEDS. 295 SCHISMOTHERIUM Ameghino. (Plates L, LI, LIII, Figs, i, 8.) Schismotheriiim Amegh.; Enumeracion sistematica, etc.; 1887, p. 21. Metopotherium Amegh.; Rev. Argent, de Hist. Nat; T. I. 1891, p. 324. The diastemata are either absent or extremely short, which imme- diately distinguishes this genus from both Hapalops and Analcimorphus, and in fact, with the exception of Pelecyodon, this is the only genus of the family so characterized. The caniniform teeth vary greatly in size and shape, but they are never large and are usually more or less trihedral in section ; L is somewhat removed from the anterior border of the maxil- lary, though not nearly so far as in Analcimorphus ; - is always styliform and either cylindrical or trihedral ; the molariform teeth are transversely oval and more or less compressed antero-posteriorly, sometimes very strongly. The skull is short and broad, with much vaulted cranium and deep postorbital constriction ; the sagittal and occipital crests are better devel- oped than in most of the preceding genera and the former curves forward dorsally in a very characteristic way. The mandible is short, with deep horizontal ramus and broad ascending ramus ; the symphysis is short and steep, the chin very abrupt and the predental beak short and broader than in any of the other genera. The fore-limb and foot are of the type common to all the family, but the manus is more isodactyl than in Hapalops. The femur is remarkable for the slenderness and roundness of the shaft, which are even more pronounced than in Analcimorphus. While more complete material of this genus is much to be desired, the evidence at hand is sufficient to show that in Schismotherium we have the somewhat modified representative of one of the most primitive members of the Gravigrada and one which is not far removed from the common ancestor of all the Megalonychidce and perhaps of the other two families also, as may be seen from the styliform -, the slender femur and the iso- dactyl feet; it is a very suggestive fact that in the Gravigrada of the Patagonian formation - is almost always styliform, and probably the absence of diastemata is also a primitive feature, but conclusive evidence on this point is lacking. The close relationship of Schismotherium with Analcimorphus is very clear, and through the latter we have the connec- tion with the Planopsidce. 296 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. SCHISMOTHERIUM FRACTUM AmeghinO. (Plates L; LI, Figs, i, 4, 4*1; LIII, Figs, i, 8.) Schismotherium fractum Amegh. ; Enumeracion sistematica, etc.; 1887, p. 21. In the Princeton Museum this species is represented by two skulls (Nos. 15,344, 15,524), a mandible without teeth (No. 15, 361) and by a leftramus mandibuli, with the teeth in place (No. 15,901), all of which were obtained by Messrs. Hatcher and Peterson at Killik Aike. In addition to this there is in the Ameghino collection a fine skull, with mandible and fore-limb nearly complete, while the type-specimen in the La Plata Museum is suffi- ciently characteristic for the satisfactory identification of other specimens. In both upper and lower jaws the teeth form almost continuous series, though short interspaces divide them, slightly longer between - and - ; - is quite small, caniniform, laterally compressed and narrow, plane on the inner and convex on the outer side and with obliquely truncate masticat- ing surface ; - has the styliform character which is so constant in all this group of genera ; in the present species it is usually subcylindrical or slightly oval, with principal diameter antero-posterior ; -, the largest of the series, is transversely oval ; - and -1, also oval, diminish successively in size. In the mandible T approximates an equilateral triangle in section, but is sometimes very small and subcylindrical ; ? and * are transversely elliptical and of nearly equal size, and * is usually cylindrical, but may be oval like ^, though always less compressed antero-posteriorly. MEASUREMENTS. No. 15,3^4. No- i5,524- Upper dentition, length 039 " " A-A 031 .031 -L, length (/'. e., antero-posterior diameter) 007 " width (i. e., transverse diameter) 005 £, length 008 .008 " width 007 .007 •S-, length 009 .006 " width 01 1 .01 1 4, length 006 .006 " width 009 .010 *-, length 006 -0055 " width 007 .008 EDENTATA OF THE SANTA CRUZ BEDS. 297 MEASUREMENTS. No. 15,361. No. 15,901. Amegh. Coll. Lower dentition, length 031 .033 .032 j_T 024 .024 .024 r, length 006 .0065 .008 " width 005 .0045 .006 -%, length 007 .006 .006 " width 009 .009 .010 3, length 008 .0065 .006 " width OIO .010 .010 -f, length 009 -0075 .008 " width 009 .009 .008 N. B. Some of the discrepancies in this table are due to the fact that in No. 15,361, and No. 15,344, except in the case of —, the dimensions are taken from the empty alveoli. The skull (Plates L ; LI, fig. 4), though varying considerably in differ- ent individuals, is one of the most characteristic in the entire series of Santa Cruz Gravigrada ; its appearance is much changed in those indi- viduals which have undergone even a slight amount of vertical compres- sion, which diminishes the remarkable elevation and vaulting of the cra- nium (compare figs, i and 2, PI. L). This skull is peculiar in its low occiput, high and dome-like cranium, short and deep postorbital constric- tion, broad forehead and short, wide rostrum. The upper contour is quite sinuous ; it rises more or less steeply to the parietal eminence, which is somewhat farther forward than the glenoid cavity ; from this point, the line, sometimes concave, descends to the postorbital constriction, becom- 'ing convex over the forehead and descending gently to the end of the rostrum. Seen from above, the aspect of this skull is equally character- istic, the anteriorily inclined occipital crest curves forward in the middle dorsal region, invading the roof of the cranium ; the short postorbital constriction is deep and abrupt, the skull rapidly broadening again to the forehead, which has temporal ridges that are much more prominent in some individuals than in others ; the lachrymals are only moderately prominent and the preorbital fossae are not visible from above ; the ros- trum is short, narrowing slightly forward, blunt at the end and some- what decurved, recalling the shape seen in many rodents. The occipital surface, which has a forward inclination, is broad and unusually low ; the ventral portion is transversely convex and is produced outward above the foramen magnum, giving the latter a tubular form, 298 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. while the dorsal portion is convex on the sides, with a broad, shallow median concavity, where it extends forward between the parietals ; later- ally, the occipital crest is prominent, rugose and heavy, dorsally it curves forward around the median concavity already mentioned and becomes very much thinner, but remains distinct and clearly demarcates the supra- occipital from the parietals ; the condyles are small and sessile, project- ing little behind the plane of the occiput and rather more below the cranial axis. The basioccipital is long, broad, and concave transversely, with a shallow, median depression, which deepens forward ; the paroccipital processes vary much, as they may be entirely absent, or unusually prominent. A narrow strip of the periotic is exposed on the surface, ending ventrally in the usual, cylindrical mastoid process, with its facet for the stylo-hyal. The basisphenoid is broad and nearly plane, except posteriorly, where it is con- cave ; both this bone and the presphenoid are left largely exposed by the pterygoids ; the orbito-sphenoid, which is quite large, is deeply impressed by a fossa, into which the spheno-palatine, optic and anterior lacerated foramina open. The parietals are large, but not very long, and support a sagittal crest, which is low and thin, especially over the parietal eminence. The squa- mosal is relatively small ; it forms a considerable part of the occipital crest, the ventral end of which is thickened into the usual tubercle ; no distinct posttympanic process is present; the zygomatic process is short and slender and is bent outward so abruptly that its posterior end forms a distinct angulation with the cranial wall. The lachrymals have the shape common to this group, but are rather smaller and less prominent than usual, an appearance which is due to the shortness of the zygomatic pro- cesses of the maxillaries and to the breadth of the rostrum ; the foramen proper is small, but a wide, funnel-shaped depression leads into it. The frontals have the ordinary hour-glass form, which is exaggerated by the depth and abruptness of the postorbital constriction ; the forehead is short, broad and nearly flat ; the sagittal crest, which extends over half the frontals, bifurcates into low temporal ridges, which curve abruptly outward and end in obscure angulations, the postorbital processes ; ven- trally, the frontals are strongly incurved and take part in the fossae into which the anterior cranial foramina open ; the nasal suture is a narrow and deep emargination of the frontals, producing a short nasal process on EDENTATA OF THE SANTA CRUZ BEDS. 299 each side. The nasals are long and narrow and quite convex in both directions ; they are narrowest at the frontal suture and, broadening regu- larly forward, are widest at the anterior end ; there is no lateral notch or process, but each nasal is obliquely truncated, so as to form a short, blunt, median point. The premaxillaries are not known, but the facets for them upon the maxillae indicate that they probably resemble those of Hapalops in shape, except for their extreme shortening. The preorbital portion of the maxillaries is rather long, owing to the posterior position of the orbit; the preorbital fossa is usually small and shallow, though it is sometimes well defined, and is always very narrow ; the dorsal portion of the maxillary is incurved and forms much of the roof of the nasal cham- ber; the zygomatic process of the maxillary is much less prominent than in Hapalops and the infraorbital foramen is narrow, hardly more than a slit. The bony palate and posterior nares show no important differences from those of the latter genus. The cranial foramina differ from those of Hapalops in only a few par- ticulars ; the optic foramen is placed lower down and nearer to the fora- men lacerum anterius, which is farther removed from the united foramina rotundum and ovale ; the glenoid foramen appears to be wanting, and the venous foramina along the parieto-squamosal suture are few and inconspicuous. The mandible has a very short, deep and thick horizontal ramus, with strongly convex ventral border ; the predental beak is very short and at the anterior end is broader than in any of the preceding species; the symphysis is very short and the chin almost vertical. The ascending rami are convex externally and concave internally, a peculiarity which is not repeated in any other contemporary genus ; the anterior border of the ascending ramus is quite broad at the base and is made concave by the prominence of the linea obliqua interna; the coronoid, which varies much in' height, is incurved, recurved and bluntly pointed, and the sigmoid notch is narrow and shallow ; the condyle is set upon a long neck and is curved mesially, presenting inward almost as much as upward ; of the angle only enough is preserved to show that it was inflected. The postero-external opening of the dental canal is at the base of the linea obliqua externa; the mental foramen is single and presents forward. 3OO PATAGONIAN EXPEDITIONS: PALEONTOLOGY. MEASUREMENTS. Amegh. Coll. No. 15,344. No. 15,524. Skull, length in median basal line .099 " " condyle to anterior nares 120 .118 Cranium, length to edge of orbit 100 .094 .089 Face, length orbit to anterior nares . . % 024 .025 Skull, width at zygomatic processes .047 .048 " " " postorbital constriction .029 .030 Occiput, height 041 .035 .039 width at base .047 .05 1 Zygomatic arch, length .070 Palate, length in median line .042 width at 1 .019 "1 .014 .016 "A .0115 .012 Amegh. Coll. No. 15,39 f. No. 15,901. Mandible, length from condyle 07 5 " of predental beak 014 depth below ^ 026 .024 .029 thickness below ^ .013 .015 depth behind ? 021 .019 .023 height of coronoid 053 .050 A specimen (No. 9,244, Plate LIU, fig. 8) in the American Museum of Natural History, consisting of the last two thoracic vertebrae, the entire lumbar series, sacrum and pelvis, may be provisionally referred to this species. It may, however, be assignable to a large species of the nearly allied genus Pelecyodon. The two thoracic vertebrae have short but heavy centra, with small foramina opening on the ventral side, very short neural spines, which are strongly inclined backward and thickened at the tip, especially on the penultimate vertebra; the very short transverse processes bear facets for the rib-tubercles, even on the last thoracic ; ac- cessory articular processes are found only in the form of a pair of small additional postzygapophyses on the last vertebra, a very marked contrast to Hapahps ; the metapophyses also are much smaller than in the latter. There are five lumbars, a larger number than has been observed in any other contemporary species of the Gravigrada. The centra of these ver- tebras increase in length to the third and then diminish, but become broader and more depressed to the last ; the ventral foramina are conspicuous on all of them, despite the completely adult state of the animal, and are espec- ially large on the second and fifth. The neural spines are remarkably EDENTATA OF THE SANTA CRUZ BEDS. 30! different from those of Hapalops, being very much lower, narrower and more inclined, each one overhanging the vertebra behind it, and much thickened at the free end ; the transverse processes also are much shorter than in the last named genus and are more elevated, projecting obliquely upward ; except on the first lumbar, they are very broad and are some- what thickened at the distal end. The accessory zygapophyses are of the type common to all the family and the metapophyses are small. The sacrum consists of five vertebrae and its only noteworthy feature is the fact that the ridge formed by the coalesced neural spines is very low. The pelvis is very similar to that of Hapalops, with a few minor dif- ferences. Thus, the ilium has a somewhat more concave gluteal surface, which presents more obliquely and less dorsally ; the sacro-sciatic foramen is larger, especially in the dorso-ventral diameter ; the pubis and descend- ing process of the ischium are longer, making the posterior pelvic opening higher and narrower, and the obturator foramen is larger and of a more oval shape. MEASUREMENTS. Last thoracic, length of centrum 018 Third lumbar, height of neural spine. . . .030 " " width of anterior face . . . .022 " " width of spine at tip 020 width over transverse Fifth lumbar, length of centrum 02 1 processes 040 " " width of anterior face 026 height of neural spine ... .028 " width over tranverse width of spine at tip 013 processes 070 Lumbar region, length 144 " height of neural spine. . . .027 First lumbar, length of centrum 018 " " width of spine at tip 021 width of anterior face 023 Sacrum, length 105 " width over transverse pro- First sacral, width of anterior face 030 cesses 06 1 Last sacral, width of posterior face 025 height of neural spine 030 Pelvis, length 204 width of spine at tip 016 " greatest width 208 Third lumbar, length of centrum 022 Ilium, length 1 28 " width of anterior face ... .025 " greatest width 079 " width over transverse Ischium, length 076 processes 052 Posterior pelvic opening, width 08 1 In the Ameghino collection is a well preserved fore-leg and foot ; the bones resemble those of Hapalops, with certain minor differences. The humerus is of nearly the same length as that of H. elongatus, but some- what heavier, and the deltoid area is distinctly less prominent, while the internal epicondyle and supinator ridge are better developed. The radius is so like that of the latter as to require no description. 302 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. The manus, which has been figured by Ameghino ('98, fig. 69), differs from that of Hapahps in a number of details. The scaphoid is even shorter proximo-distally, especially on the radial side ; it appears not to touch the magnum at all, though it is difficult to make quite certain of this. The lunar is shorter and its exposed dorsal face is more regularly quad- rate ; it does not extend below the pyramidal and apparently does not touch the unciform. The pyramidal is somewhat longer and more cubical ; the magnum is larger and its dorsal face is more regularly pentagonal, while the unciform is longer and hardly so deeply notched for metacarpal III. FIG. 35. Schismotkerium fractum. Mand- ible, crown-view, x -j. Amegh. Coll. FIG. 36. Schismotherium f me tit in . x \. Amegh. Coll. Left manus, In the metacarpus the most obvious difference from Hapalops is the more equal length of metacarpals II, III and IV, the distal ends of which lie in nearly the same transverse line, while in the latter genus the line connecting the distal ends of the same three metacarpals is very oblique, owing chiefly to the great elongation of IV. Metacarpal I is the shortest of the series and quite stout ; II is relatively shorter and heavier than in Hapahps, and III is not only heavier, but also has a far more massive EDENTATA OF THE SANTA CRUZ BEDS. 303 process which abuts against the unciform. Metacarpal IV is much more slender than II or III and somewhat shorter, a marked difference from Hapalops ; V also is much shorter than in the latter and a little stouter in proportion. The phalanges of the first and second rows differ very little from those in the last named genus, but the unguals are broader at the proximal end, less compressed and not so sharply pointed ; in order of size the arrange- ment would be, III, II, IV, I, V. ' Associated with the skull, No. 15,524, was found the proximal half of a femur (Plate LIII, fig. i), so unlike that of the other Santa Cruz Gravi- grada as to raise a suspicion that the association was accidental. How- ever, the femur of Analcimorphus serves to connect that referred to Schismotherium with the usual gravigrade type. The head is hemispherical, set upon a distinct neck, rising far above the great trochanter and presenting proximally more than internally ; its surface is smooth, without sulcus for the round ligament ;. the great tro- chanter is low and massive and, on the posterior side, it forms a broad, elongate ridge, enclosing a very small digital fossa ; the second trochanter is a prominent, heavy and rugose tubercle, and the third is also very prominent. Aside from the shape and position of the head and the absence of the pit for the round ligament, the great peculiarity of this femur is in the form of the shaft, which is not antero-posteriorly com- pressed and flattened, as it so universally is among the Gravigrada, but tends to the cylindrical shape common to most mammals. MEASUREMENTS. Humerus, length 138 Metacarpal II, length 021 " width of proximal end 037 " " width of proximal end .0105 " " " distal end over epi- " " " " distal end... .009 condyles 066 Metacarpal III, length 021 " " distal trochlea .».. .029 " " width of proximal end .017 Radius, length .120 " " " " distal end. . . .010 width of proximal end 019 Metacarpal IV, length 020 " " distal end 021 " " width of proximal end .006 Carpus, proximo-distal length in " ." " " distal end... .006 median line 015 Metacarpal V, length 012 " width 033 " " width of proximal end . . ?.OO5 Metacarpal I, length oio " " " " distal end 006 " width of proximal end. . .006 Ungual phalanx, digit I, length 018 " " distal end 006 " II " 033 304 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. MEASUREMENTS. Ungual phalanx, digit IV, length 026 Femur, width of shaft above third tro- " " "V " 01 1 chanter 030 Ungual, digit III, proximal width oio " thickness of shaft above third Femur, width of proximal end 056 trochanter 022 SCHISMOTHERIUM SPLENDENS (Ameghino). (Plate LI, Figs. 2-3*.) Metopotherium splendens Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 324. In the Brown collection, American Museum of Natural History, is a representative of this species (No. 9,247) which agrees very well with the type, and consists of a skull without mandible and lacking the cranial roof, associated with the atlas, ulna and fibula. Another individual in the Princeton Museum (No. 15,590, a skull lacking the occiput, basis cranii and mandible, found by Mr. Peterson at Halliday's) is more aberrant, but almost certainly referable to the same species. The dentition varies much in the different individuals, but, neverthe- less, displays certain constant differences from that of S. fractum. The upper caniniform (~) is small, recurved, of longitudinally elliptical section and usually is obliquely worn, but in the Princeton specimen this tooth is extremely small and protruded but little below the level of the alveolus, and the exposed portion is not recurved, but straight and horizontally abraded ; the great reduction of - in this individual is probably a sexual character. The space between A and - almost deserves the name of an ex- tremely short diastema and in all known examples is longer than in the preceding species. The second upper tooth is styliform and may be sub- trihedral or subquadrate in section ; the three succeeding teeth are trans- versely oval, diminishing in size from ^ to *-, which is the smallest of the molariform series. These teeth are broader and more antero-posteriorly compressed than in S.fracttim, notably so in No. 9,247, in which this fea- ture is exaggerated. In the subjoined table the measurements of the type are, except in the case of - and -, taken from the empty alveoli. MEASUREMENTS. Type. No. 9,247. No. 15,590. Upper dentition, length 038 .038 .038 " " " 2.-6. O3O .O3O .030 -L, length (i. e., antero-posterior diameter) 005 .006 .004 EDENTATA OF THE SANTA CRUZ BEDS. 305 MEASUREMENPS. Type. No. 9,237. No. 15,590. " width (*'. e., transverse diameter) °°35 -OOSS -3 2, length 0075 .0063 .0063 " width 0065 .006 .0065 2-, length 008 .006 .0063 " width oio .0105 .010 A, length 0065 .006 -0055 " width OO9S -Oio .009 -5-, length 0035 .005 .005 " width 007 .009 .008 The skull has certain constant differences from that of S. fracttim. As in the latter, the occiput is low and from it the upper contour of the skull rises quite steeply to the parietal eminence, though the cranium is never so high and dome-like as it often is in S. fracttim ; from the eminence the profile decends very gradually and almost uninterruptedly to the end of the rostrum. The characteristic difference from the skull of the preceding species is best displayed when the skull is viewed from above ; it is then seen to have a narrower and more elongate cranium, with much better defined sagittal crest and temporal ridges, longer, shallower and less abrupt postorbital constriction, shorter and less tapering rostrum. The occipital surface is relatively narrower than in S. fracttim, with thinner and less prominent crest, which, though curved forward between the parie- tals, does not form so deep an embayment ; the foramen magnum is more circular and the condyles less sessile. The parietals are relatively broader and the squamosal is narrower, and its zygomatic process even shorter. A fragment of the jugal is connected with No. 9,247 and differs in some respects from that of any other Santa Cruz species in which this element is known, displaying a curious resemblance to the jugal of Glossotherinm as figured by Reinhardt ('79, Tab. I); the anterior end is broadened into a hammer-like head for articulation with the maxillary and lachrymal, then, for a short distance, the bone becomes very slender, expanding again into the plate-like suborbital process, which is narrower than in Glossotherium, but has similar raised borders, with a depression between ; the posterior part of the jugal must have been longer than in the Pleistocene genus, as is shown by the zygomatic process of the squamosal. The frontals have less of the hour-glass shape than in S. fradum, owing to the shallowness of the postorbital constriction ; they have a shorter, wider sagittal crest and much more prominent temporal ridges ; anteri- 306 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. orly, the frontals are less deeply emarginated by the nasals and the nasal processes are extremely short; the forehead is narrower, longer, more lozenge-shaped and very gently concave. The nasals are shorter and of a slightly different shape ; posteriorly they are broader and less pointed and are throughout of more uniform width, though the anterior ends are slightly broadened, extending somewhat beyond the maxillaries, and have very wide, shallow notches, with hardly perceptible median point. The maxillaries have better defined and larger preorbital fossae than in S. fractum and the median notch of the palate for the premaxillary spines is broader and shallower; the palate is somewhat narrower and more convex behind than in the latter species and widens more anteriorly. MEASUREMENTS. Skull, length in median basal line " condyles to anterior nares Cranium, length condyle to anterior edge of orbit. . . . Face, length orbit to anterior nares Cranium, width at zygomatic processes width at postorbital constriction Occiput, width at base Rostrum, width at infraorbital foramen " " anterior end Zygomatic arch, length Palate, length in median line width at 1. . " 3. " SL Type. .100 .118 •093 .027 .051 •033 .046 .030 .025 .065 .015 .012 No. 9,247. No. /5,jpo. .101 .119 .095 .027 .044 .029 .046 .032 .027 .066 .040 .021 .OI4 .0095 .026 .044 .030 .031 .028 •039 .OI9 .OI4 .Oil The atlas is higher and narrower proportionately to length than in Hapalops; the anterior cotyles are very small and are given a kidney- shape by a sulcus which invades each from the mesial side, and the pos- terior cotyles are extremely narrow; the neural arch is broad, thin and strongly upcurved, making the canal very high, and has no spine ; the inferior arch is narrower, straighter and without hypapophysis. The ulna is relatively longer and more slender than in Hapalops and has a shorter olecranon and shallower sigmoid notch ; the shaft is straighter and the distal end larger, with a projection for the radius which is not present in the genus last named. The fibula is remarkable for the antero-posterior extension of the prox- imal end and the large size of the tibial facet ; the shaft is laterally com- EDENTATA OF THE SANTA CRUZ BEDS. 307 pressed and of almost uniform diameter, except near the distal end, where it is much enlarged ; the distal end is very heavy, less elongate than in Hapalops, with notably smaller tibial and more nearly plane astragalar facet. MEASUREMENTS. Atlas, length 022 Fibula, length 114 " dorso-ventral height 026 " thickness of proximal end 023 Ulna, length 141 " width of shaft in middle 0065 " " of olecranon 015 " thickness of shaft in middle . . . .0095 " width of humeral trochlea 019 '" width of distal end 020 " " " distal end 0125 " thickness of distal end 025 PELECYODON Ameghino. (Plates LII, LIII, Figs. 2 7.) Pelecyodon Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 323. Uranokyrtus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 159. Adiastemus Amegh. ; Ibid, p. 160. Although closely allied with Schismotherium, Pelecyodon is a well dis- tinguished genus. The dentition is especially characterized by the shape of the upper caniniform, which is much compressed laterally and extended antero-posteriorly and is plane on the inner, convex or angulate on the outer face ; in some examples this tooth is abraded only on the posterior face, in others it is bevelled to a sharp point; it is inserted somewhat hearer to the anterior edge of the maxillary than in the preceding genus. The teeth are implanted in nearly continuous series, but with slightly longer interspace between - and - than between the succeeding teeth. The second upper tooth, -, is more or less cylindrical, but rather narrower in front than behind ; z, -, and - are transversely oval, a the largest and •* much the smallest of the series. In the lower jawf T is small, laterally compressed and of elliptical or obscurely trihedral section, and is sepa- rated from ? by an even shorter space than that between - and - ; ? and * are transversely oval and \ is subcylindrical. The skull is longer and narrower than in Schismotherium, but the orbit is slightly more advanced and the face is therefore somewhat shorter ; the sagittal crest is well defined and the occipital crest is thin, but more or less prominent, and its median dorsal portion is but slightly curved for- 308 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. ward, a marked and constant difference from the preceding genus. The mandible has a short horizontal ramus and a short predental beak, which is narrower and more pointed than in Schisniotheriiim. Ameghino has called attention to a remarkable feature of the mandible in this genus and its allies, viz., the division of each horizontal ramus into two elements which are suturally connected. "En outre, dans certains genres (Pele- cyodon, Metopotherium, etc.) les branches mandibulaires sout formees par deux pieces distinctes, une ant£rieure et 1'autre posterieure ; ces deux pieces sont unies par une suture qui part du bord alveolaire, a peu pres vers la moitie de la longeur de la serie dentaire, et se dirige obliquement en arriere et en bas pour se terminer dans le bord inferieur a peu pres au- dessous de la derniere dent. Cette suture, qui sans doute estun caractere herite des reptiles, disparait de bonne heure ; pourtant, dans quelques especes, elle est persistante " ('94", 141; 160, fig. i). It is true that an appearance of such a suture maybe observed in certain mandibles, but the appearance is not conclusive or convincing. At all events, it cannot well be an inheritance from the reptiles, for in that group the dentary bone is not divided. The skeleton of the present genus is incompletely known and only in connection with P. arcuatus. The cervical vertebrae are small and lightly constructed, otherwise differing little from those of the smaller species of Hapalops. The trunk vertebrae are remarkable for the short, slender, backwardly directed neural spines, which are of curiously uniform length and thickness throughout the series, though becoming somewhat longer in the posterior thoracic and lumbar regions. The humerus resembles that of Hapalops, except that the deltoid area is less developed than in any of the other known Santa Cruz Gravigrada ; the ulna is short and slender and in the manus digits IV and V are more reduced than in any other contemporary genus of the order. The femur differs from that of Analci- morfitiusa.nd Schismotheritim in having the broad, antero-posteriorly com- pressed shaft, but has an unusually small third trochanter ; the tibia resem- bles that of Hapalops, except that the astragalar surface is nearly plane. The pes is remarkable for the great size and thickness of digit III, which has a relatively enormous claw ; as in Analcinwrphus, metatarsal IV is but little longer than II and III, while V is much reduced and has no such process from the fibular side of the proximal end as characterizes Hapahps EDENTATA OF THE SANTA CRUZ BEDS. 309 PELECYODON CRISTATUS Ameghino. (Plate LII.) Pelecyodon cristatus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, P- 323- Pelecyodon robustus Amegh., Ibid. This is a very variable species, with a considerable range of difference in size, in the proportions of the teeth, etc., but the individuals grade into one another so completely that it is impracticable to separate them. In the type-specimen - is much compressed laterally, extended antero-posteriorly, forming in cross-section an elongate, very narrow oval ; the grinding sur- face is bevelled to a sharp point by abrasion on both sides ; a second individual, belonging to the La Plata Museum, appears, from the shape of the empty alveolus, to have this tooth of similar form, but somewhat broader transversely ; in other individuals, again, the transverse width of the tooth is greater, the antero-posterior length is less, while the abrasion is only on the posterior side. The second upper tooth is subcylin- drical, varying only in size and in the nar- rowness of the anterior face, which is never so broad as the posterior ; - and - are trans- versely oval and - is very small and may or may not be made reniform by a vertical groove on the posterior face ; in the same specimen this groove may be present in - of one side and not of the other. In the mandibular dentition y is small and long- itudinally elliptical or trihedral ; ? and -j are transversely oval and T is subcylindrical. FIG. 37. Pelecyodon cristatus. Mandible, crown-view, x \. Amegh. Coll. MEASUREMENTS. Type, L. P. Museum. No. 15,049. No. 1 Upper dentition, length 037 .032 .040 .035 " " " A-A 027 .023 .030 .025 J-, length (i. e., antero-posterior diameter) 008 .008 .0073 .006 " width (t. e., transverse diameter) 004 .0045 .0043 .005 3IO PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. MEASUREMENTS. Type. L. P. Museum. No. 1^,04.9. No^ A, length 007 .007 .006 " width 006 .0063 .005 3 £, length 0053 .005 .006 .0053 " width 0083 .008 .009 .008 A, length 005 .005 .006 .005 " width 0073 .0065 .0085 .0065 *, length 003 .0025 .0043 .0033 " width 007 .005 .0073 .007 Type. No. 2. Type of P. robustus. Lower dentition, length 028 .026 .027 " " " j_? 022 .020 .021 T, length 006 .007 -0055 " width 002 .003 5 .004 j, length 006 .005 -0055 " width 009 .008 .009 j, length 007 .005 .0065 " width 009 .007 .010 T, length 007 .0065 .0065 " width 008 .005 $ .008 In specimens that have not been distorted by pressure the profile of the skull resembles that of Schismotherium splendens, the upper contour rising even more steeply to the parietal eminence and thence descending gently and uninterrupedly to the end of the rostrum ; the occiput is low, inclined slightly forward, and convex, save in the median dorsal region, where it becomes slightly concave, though very much less than in Schismotheritim and hardly at all in some specimens ; the median vertical ridge which runs from the occipital crest nearly to the foramen magnum is much more prominent in some individuals than in others ; the occipital crest is well defined, but very variable in degree of prominence ; the foramen magnum is small and subcircular, and the condyles are small, sessile, and projecting little behind or below the occiput ; the fossa between the exoccipital and squamosal is much deeper than in Schismotherium. The tympanic is of the usual type, a loosely attached, incomplete ring. The parietals differ little in their proportions from those of Schismo- therium splendens ;. the sagittal crest is usually a thin ridge, but in the type-specimen its posterior portion is a narrow area, as in the last named species ; the crest is continued for a considerable distance upon the fron- tals, dividing into faintly marked temporal ridges, which are even more EDENTATA OF THE SANTA CRUZ BEDS. 31 I obscure than in S. fractum ; the postorbital constriction is much shallower and less abrupt than in the latter. The squamosal is long and low and the tubercle at its infero-lateral angle is unusually prominent ; the zygo- matic process is short and weak and near its base is pierced by a vascular foramen. The lachrymal is less prominent than in most of the genera. The facets for the premaxillae on the maxillaries indicate that they were somewhat different from those of Schismotherium ; the surface for the postero-external branch is larger and rises higher upon the sides of the anterior nares and the notch for the spines is deeper and narrower. The preorbital portion of the maxillaries is shorter than in Schismotherium and the fossae deeper than in S. splendens ; the bony palate is of nearly uniform width. The posterior nares differ from those of Hapalops in having lower side walls. The mandible resembles that of S. fractum in appearance, but is lighter and more delicate ; the ventral border of the horizontal ramus is but slightly convex ; the symphysis is short and the predental beak is short, narrower and more pointed than in S. fractum ; the ascending ramus is very much thinner than the horizontal, producing a peculiar angulation of the jaw. MEASUREMENTS. Type. L. P. Museum. No. 15,04.9. No. 15,627 Skull, length in median basal line .098 " " condyle to anterior nares .094 .116 .108 Cranium, length condyle to edge of orbit. .. .089 .080 .098 .089 Face, length orbit to anterior nares .016 .020 .021 Occiput, height 030 .028 .035 . .034 width at base 039 .040 .046 Cranium, width over zygomata 039 -O39 -°47 " at postorbital constriction .. .023 .024 .031 Zygomatic arch, length .053 .069 .063 Palate, length in median line .038 " width at 1 015 .016 .017 .019 " " -1 012 .013 .015 .013 " & OIO .OIO .OI2 .OI2 In the La Plata Museum is a curious jaw-fragment, evidently patho- logical and probably referable to this species. As the result of inflamma- tion, the horizontal ramus is swollen and pitted on the outer side and the process has given an abnormal character to ^. The anterior half of this tooth, which is considerably narrower than the posterior, is composed of 312 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. two columns, of which the external is much larger and is placed in the median line of the tooth, with a broad shallow groove on its outer face ; the internal column is very much smaller and is sharply defined by deep vertical grooves in front of and behind it ; ^ is of the ordinary transversely oval shape, but has a distinct, vertical sulcus on the inner side ; T is sub- cylindrical and quite normal. PELECYODON PETR^EUS Ameghino. Pelecyodon petrceus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, P- 323- This species is as yet represented only by the type specimen and, although distinguished merely by the form of the teeth (usually a very uncertain criterion) is probably valid. Its peculiarities are not connected by transitional forms with the other species, but, on the contrary, give it an isolated position. On the left side, A is shaped much as in P. cristatus, elongate antero-posteriorly and much compressed laterally, while on the right side it is relatively broader ; *• is narrower anteriorly than in the pre- ceding species and thus has a more trihedral form ; ^ is remarkable for its shortness antero-posteriorly and transverse width and is in marked con- trast to the shape of this tooth in the other species of the genus ; - is smaller, but of similar, exceptionally short and broad form ; - is very small but relatively very wide. The following dimensions are from a photograph of the type, right side. MEASUREMENTS. Upper dentition, length 032 %-, length 0045 " £--5 023 " width 0095 J-, length (t. f., antero-posterior diam- A, length 0035 eter) 0065 " width 009 " width (t. f., transverse diameter) . . . .0035 &, length 002 3, length 0x565 " width 006 " width 006 PELECYODON ARCUATUS Ameghino. (Plate LIII, Figs. 2-7.) Pelecyodon arcuatus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, P- 323- In the collection of the American Museum of Natural History is a specimen (No. 9,240) which agrees closely with the type of this species. EDENTATA OF THE SANTA CRUZ BEDS. 313 It consists of the mandible, with dentition complete ; four cervical, sixteen thoracic, one lumbar and two caudal vertebrae; the right scapula and humerus, left ulna and part of manus ; the right ilium and femur ; both tibiae and the greater part of the pes. The skeleton is much more distinct from that of the other genera than would have been expected from the teeth and skull only. The dentition is not especially characteristic; T is very slender, of longitudinally elliptical section, with major axis somewhat oblique to the line of the other teeth, while the crown is erect and quite high. Although the alveoli of T and ^ are separated by a very thin lamina of bone, the space between the teeth themselves is greater than between any succeed- ing pair, because neither tooth completely fills its socket ; ^ is large, much compressed antero-posteriorly and transversely oval, with major axis' oblique to the line of the dental series ; ¥ is similar, but slightly larger and less oblique; T is subcylindrical, especially in the type, while in 9,240 it is more of an oblique oval. MEASUREMENTS. Type. No. 9,24.0. Lower dentition, length 03 1 .03 1 " j_3 022 .023 T, length (t. e., antero-posterior diameter) .005 " width (i. e., transverse diameter) .004 2 , length 005 5 .006 " width oio .008 -g, length 007 .0065 "' width 0095 .0085 T, length 0075 .007 " width 0095 .009 The mandible differs in several respects from that of P. cristatus, espe- cially in the much greater sinuosity of the ventral border, being more convex under the horizontal ramus and much more concave under the ascending ramus ; the sudden thickening of the former at its posterior end projects more externally in P. cristatus and more internally in the present species ; the angular process is very long and prominent, extend- ing well behind the condyle, and is broader dorso-ventrally than in P. cristatus; its ventral border is but slightly inflected, much less than in the large contemporary genera. The condyle is placed upon a shorter neck than in the species last named and projects more upward, less back- 314 PATAGONIAN EXPEDITIONS! PAL/EONTOLOGY. ward; the sigmoid notch is narrower and deeper and the coronoid pro- cess is somewhat narrower and more recurved, and the postero-external opening of the dental canal has a somewhat more inferior and anterior position. The predental beak is considerably longer than in P. cristatus, but its dorsal border does not, as in the latter, rise above the level of the teeth, and the contour of the chin is quite different, rising less steeply from the ventral border, with its anterior part continued forward more horizontally. MEASUREMENTS. Mandible, length from angle 105 Mandible, distance angle to T 053 height of condyle 039 length of predental beak 023 •• " " coronoid 049 " depth of ramus below ^ 023 distance condyle to ? 045 breadth over angular processes .05 i The cervical vertebrae are very small ; they resemble those of the smaller species of Hapalops, but are more delicate, with more slender transverse processes and neural arches, and short, weak neural spines. The thoracic vertebra:: are quite characteristically different from those of Hapalops; in the anterior part of the thorax the vertebrae have very small centra, which increase posteriorly in size, but this increase is rela- tively less than in Hapalops ; only on the centrum of the last thoracic are the ventral foramina visible. The most peculiar feature of these vertebrae is the form of the neural spines, which throughout the region vary little in size, shape and inclination ; as compared with those of a small species of Hapalops, they are much shorter, more slender and more steeply inclined. The small, uniform size and almost unchanging degree of inclination of the spines give to this vertebral column an appearance which is conspicuously different from that of most of the other Santa Cruz Gravigrada. The transverse processes are very short; the zyga- pophyses do not differ from those of other members of the family, the accessory pairs appearing on the last two thoracics. The only lumbar preserved, and in an incomplete state, is the first ; in this the ventral foramina are much more conspicuous than on the last thoracic. Of the two incomplete caudal vertebae found with this specimen, one is from the anterior part of the tail, probably the fourth or fifth of the series, and the other is from the hinder portion ; these vertebras indicate a tail very similar in its proportions to that of Hapalops. EDENTATA OF THE SANTA CRUZ BEDS. 315 A single segment of the mesosternum is preserved ; the body, or dorsal part, of the segment is relatively short, broad and thin, but the ventral projection which carries the facets for the tubercles of the sternal ribs is exceedingly prominent. MEASUREMENTS. ? Fourth thoracic, length of centrum. . . .015 Last thoracic, length of centrum 017 width of anterior face . .014 width of anterior face.. .023 " " posterior face .017 " " posterior face. .026 " over transverse " over transverse processes 035 processes 040 height of neural spine " height of spine from from centrum 02 1 centrum 029 width of neural spine " width of spine at base. . .019 at base 015 " " " ' tip ... .0115 width of neural spine at tip oio The scapula has lost the distal epiphysis with the coracoid, and the glenoid border is much broken, but the shape of the bone is evidently different from that of Hapalops in its shortness and breadth ; the spine, which for the proximal third of its course is hardly noticeable, is so placed as to make the prescapular fossa much larger than the postscapular, and the glenoid border is, as usual, elevated into a prominent ridge. The humerus (Plate LIII, fig. 3) also differs notably from that of Hap- alops; the head is relatively large and projects well behind the plane of the shaft, and the internal tuberosity is unusually large ; the deltoid area is less developed than in any other of the known Santa Cruz Gravigrada, and, though of the usual length, its borders are not at all prominent. The shaft is quite stout, diminishing in size distally, until it is greatly broadened by the supinator ridge ; this ridge, the internal epicondyle and the foramen are much as in the other genera, but the external epicondyle is unusually prominent. The trochlea is quite peculiar and more nearly approximates that of Megalonyx than does the trochlea of Hapalops; compared with the latter, it is narrower and more than half of its breadth is taken up by the prominent, hemispherical facet for the radius ; the ulnar facet is narrower, much more convex transversely, and its inner border is not produced into a flange ; the anconeal fossa is very small and shallow. As the ulna (Plate LIII, fig. 4) has lost both epiphyses, its length is not determinable ; the olecranon was, however, obviously shorter than that 316 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. of Hapalops and the shaft is more slender and more regularly curved, the posterior border being continuously convex. Metacarpals IV and V, the only part of the manus preserved, are sur- prisingly small and indicate either that the whole manus was very small, or, more probably, that the ulnar side was greatly reduced. Metacarpal IV is of nearly the same length as the corresponding metatarsal, but much more slender, and considerably exceeds in length metacarpal IV of Schismotherium fractum , the proximal end has a very complex facet for the unciform and on the ulnar side is a deep pit which receives the head of V ; in Hapalops this facet is much more nearly plane ; the distal trochlea is narrow, but has a very prominent carina. The fifth meta- carpal also is longer and much more slender than in Schismotherium, and the narrow proximal end is occupied by the saddle-shaped facet for the unciform ; the shaft is very slender and the distal trochlea is imperfect, with almost obsolete carina. MEASUREMENTS. Humerus, length 136 Metacarpal IV, distal width 007 " thickness of proximal end .. .032 " " " thickness 012 " width of trochlea 028 Metacarpal V, length 021 " " distal end over epi- " " proximal width 0055 condyle 060 " " thickness 0075 Metacarpal IV, length 028 " " distal width 005 " " proximal width 009 " " thickness 007 " thickness oil The fragment of pelvis merely indicates the likeness of the ilium to that of Hapalops. The femur (Plate LIII, fig. 5) lacks the proximal epiphysis, except a portion of the head, which is directed more proximally and less internally than in Hapalops; the second trochanter is very prominent, but the third is more reduced than in any other Santa Cruz genus of the order. The shaft is to some extent intermediate between the form seen in Analcimorphus and the more usual type seen in Hapalops, being shorter and broader than in the former, less flattened and with more convex sur- faces than in the latter. The tibia (Plate LIII, fig. 6) is considerably shorter than the femur; the spine is low, blunt and feebly grooved, and the cnemial process is rugose ; the shaft has a very strong anterior curvature and, on the inner side above the middle, is a prominent tubercle ; the great projection from EDENTATA OF THE SANTA CRUZ BEDS. 317 the inner side of the distal end is more massive than in the other genera. The astragalar surface is remarkably flat, and though the intercondylar tongue appears on the dorsal border, it is not continued backward as a ridge, and the facet for the inner condyle of the astragalus is very much less concave than usual. MEASUREMENTS. Femur, proximal width 044 Tibia, proximal thickness 040 " distal width 054 " least width of shaft 017 Tibia, length 114 " distal width 0395 " proximal width 05 1 " " thickness 023 Of the pes (Plate LIII, fig. 7), this individual lacks all the tarsus, except the cuboid, and the first digit. The cuboid is quite peculiar and has a very different appearance from that of Hapalops ; it is relatively long and narrow and has an oblique position in the tarsus ; the calcaneal facet is large and convex and almost lateral in position, and the astragalar facet, which is smaller than in Hapalops, meets the former at an acute angle ; on the tibial side distally and almost confined to the dorsal border, is a small oblique facet for metatarsal III ; the distal end is occupied chiefly by the large, saddle-shaped surface for the fourth metatarsal, that for the fifth being very much smaller and placed at the postero-external angle. The metatarsus most resembles that of Analcimorphus and, presum- ably, that of Schismotherium also, but with certain well defined character- istics of its own. Metatarsal II is short and massive and, though somewhat narrower in proportion to its length, is otherwise so similar to that of Hapalops as to require no particular description. Metatarsal III is somewhat shorter and heavier than II, but is not so extremely shortened as in the genus last named, and the facet for the ectocuneiform has no such deep median notch ; the proximal end is very broad, extensively overlapping the head of IV and articulating by a con- siderable facet with the cuboid, an articulation which has not been ob- served in any other Santa Cruz genus of the order. The shaft is very short, broad and thick, somewhat contracted in the middle and broaden- ing slightly at the distal end, and the distal trochlea has an immense carina. It is worthy of notice that the two sesamoids, which are attached to the plantar side of the distal trochlea, are of very different sizes, that 3 1 8 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. on the tibial side being far larger and resembling a small pisiform in ap- pearance. How far this arrangement is peculiar to Pelecyodon, cannot at present be determined. Metatarsal IV is longer and very much more slender than III, but does not exceed the latter in length so much as in Hapalops, the relative lengths of the two bones being more as in Analcimorphus, though IV is far more slender than in the latter and has a narrower proximal end than in either of the genera mentioned. Metatarsal V is far shorter and slighter than IV and indeed is much more reduced than in any of the other genera of which the foot-structure has been determined ; the proximal end is broad and thick, but the pro- cess given off from the fibular side is much smaller than in Hapalops and the distal trochlea, though small, retains a prominent carina, which has been lost in the latter genus. The phalanges are proportionately longer and lighter than those of Hapalops, and those of the various digits differ much in size ; the ungual phalanx of digit III is of relatively enormous size, much exceeding any of the others, and making this the longest, as it is by far the heaviest digit, despite the shortness of the metatarsal and of the second phalanx. The phalanges of digit IV, which approximately equal those of digit II in length, are very slender, while those of V are greatly reduced. The ung- uals are more slender, decurved and sharply pointed than in Hapalops and the distal cleft is longer and more distinct. MEASUREMENTS. Metatarsal II, length 026 First phalanx, digit II, length 013 " " proximal width 014 " " " " proximal width .01 1 " distal width 012 " thick- " " thickness 018 ness. .018 Metatarsal III, length 023 " " " " distal thickness .013 " " proximal width 024 First phalanx, digit III, length 016 " " distal width OI55 " " " " proximal width .013 " thickness ..... .0205 " " thick- Metatarsal IV, length 029 ness. .023 " " proximal width 009 " " " " distal thickness .017 " distal width 009 First phalanx, digit IV, length 012 " " " thickness 012 " " " " proximal width .010 Metatarsal V, length 025 " " " " thick - " " distal width 006 ness. .017 " thickness 0095 First phalanx, digit V, length 0095 EDENTATA OF THE SANTA CRUZ BEDS. 319 MEASUREMENTS. First phalanx, digit V, proximal width .007 Second phalanx, digit V, proximal It U thick- ness, .oil Second phalanx, digit II, length... .024 " proximal width. . . .01 1 " " " " proximal thickness .015 Second phalanx, digit III, length... .022 " proximal width ... .013 " proximal thickness .019 Second phalanx, digit IV, length . . . .022 " " " " proximal width . . .008 proximal thickness .0135 Second phalanx, digit V, length .. .012 width . . .006 " proximal thickness .0095 Ungual, digit II, length 048 " " " proximal width oio " " " " thickness . .016 Ungual, digit III, length 060 " " " proximal width ... .016 " thickness. .034 Ungual, digit IV, length P.O44 " " " proximal width oio " " thickness. .0145 Ungual, digit V, length ?.O23 " " " proximal width 006 " " " thickness . .010 Digit II, length 091 " III, " 094 " IV, " 085 " V, " 056 PELECYODON MAXIMUS Ameghino. Pelecyodon maximus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, P- 324- Adiasteimis compressidens Amegh. ; fenum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 161. The type of this species is a single tooth, which seems not to be distinct from the mandible afterwards described as Adiastemus compressidens, and represents considerably the largest species of the genus. The first lower tooth differs somewhat in size and shape in the two halves of the jaw, that on the right side being somewhat larger and more trihedral, and that on the left more elliptical ; z is very large, broad, antero-posteriorly com- pressed, and 3 is slightly wider ; T is less cylindrical than in the other species and more transversely oval, though placed obliquely to the line of the other teeth. The dimensions are from a photograph of the type of A. compres- in the Ameghino collection. 32O PATAGONIAN EXPEDITIONS: PALEONTOLOGY. MEASUREMENTS. Lower dentition, length 032 T, width, left side 003 " " " y_T 025 3-, length 006 Y length (i. e., antero-posterior diameter) " width oio right side 007 ^, length 006 " width (z. e., transverse diameter) right " width 0105 side 004 -f, length , 007 T, length, left side 006 " width 0095 PELECYODON BOMBIFRONS (Ameghino). Uranokyrtus bombifrons Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 160. The type and only known specimen of this species is the weathered facial region of a skull, with all the teeth broken to the level of the alveoli. Ameghino has referred it to a distinct genus because of the coossification of the nasals and frontals, probably an abnormality. As a species, however, it is quite well defined. In the dentition ^ is remarkably large and the two series of upper teeth are not so nearly parallel as in the other species of the genus, but converge posteriorly, making the palate more triangular and more convex behind. The dimensions are taken from Ameghino's original description ("94", 161). MEASUREMENTS. Upper dentition, length 038 £, length 007 i, length (/. e,, antero-posterior diameter) .007 " width 012 " width (i. e., transverse diameter) 004 Palate, width at i 018 i, length 008 " " " ^ 013 " width 008 " " " -6 007 PLANOPSIDsE. This term is proposed instead of the name Prepotheriidce, which Ame- ghino has employed ('94", 161), on account of the rule of nomenclature which requires that the family name shall be taken from the genus first described, and because of the grave doubt as to whether Prepotherinni is not a synonym of Planops. There is some reason to believe that the animals referred to this family may prove to be nearly related to the Megatheriidcz, to which they have several suggestive resemblances, and in that case, it would be advisable to incorporate them in the latter family, though it would be premature and perhaps misleading, to do so without fuller information. EDENTATA OF THE SANTA CRUZ BEDS. 32 1 In Santa Cruz times the members of this family were far less abundant and varied than the Megalonychidce, which they much exceed in average size ; the largest known Gravigrada from the formation belong to the Planopsida and none of them are very small. The teeth are non-lobate and the small upper caniniforms, which in all known examples are isolated by diastemata, are inserted far behind the anterior border of the maxillary. The skull is elongate and cylindrical, with no trace of a sagittal crest, but with the cranial roof more or less flattened and having some cancelli and incipient sinuses in the parietals. The premaxillae are not known, but the facets for them upon the maxillaries show that they must have been quite different from those of the preceding family, and the rostrum is longer; the palate is much less convex and rugose. In no genus of the present family is the number of trunk-vertebrae known, but there is good reason to believe that the back was very long and that the number of vertebrae was quite equal to that which is found in the contemporary Megalonychidce. A difference from the latter family is to be observed in the lumbar region, where a second pair of accessory pre- and postzygapophyses is added. The tail is extremely heavy. The bones of the fore-limb have a general resemblance to those of the preceding family, but are considerably longer in proportion ; those of the manus show many differences of detail, the most important of which is the shape of the ungual phalanges, which are much broader, more decurved and blunter than in the Megalonychida. The pelvis is chiefly remarkable for the great elongation of the pubes and ischia, which produces a decided resemblance to Megatherium. The femur is extremely broad and antero-posteriorly compressed and flattened, much more so than in the preceding family, while the tibia differs less from that of the latter. Little is known of the pes, but the calcaneum and astragalus have certain very significant characteristics. As compared with those of the Megalonychidce, the following differences may be noted : (i) the astragalus has entirely different proportions, being much shorter and broader ; (2) the inner condyle is much shorter proximo-distally, strongly convex and projecting prominently towards the inner side ; this is obvi- ously the first stage in the remarkable transformation of the astragalus which characterizes Megatherium; (3) the calcaneum has a much more prominent sustentaculum, the astragalar surface of which presents dorsally instead of distally, and the cuboid facet is very narrow dorso-ventrally. 322 PATAGONIAN EXPEDITIONS : PAL/GONTOLOGY. Evidently the significance of these differences is that a beginning had been made in the rotation of the foot, so as to bring the weight upon the fibular border. PLANOPS Ameghino. (Plates LVIII ; LIX, Figs, i-i6.) Planops Amegh. ; Enumeracion sistem., etc., 1887, p. 23. Schismotherium Mercerat, in part; Rev. del Museo de La Plata, T. II, 1891, p. 8. In the collection of the American Museum of Natural History is the greater part of a skull of P. longirostratus and in the Princeton collection is a nearly complete skull, lacking the mandible, of a new and much larger species ; both skulls represent quite immature animals, as all the sutures are still open. These specimens give us much welcome informa- tion regarding a genus which has hitherto been so imperfectly known, but of the skeleton nothing has yet been found. The dentition is characteristic and seems to be unusually constant ; - is small, cylindrical and caniniform ; it is implanted very far behind the anterior border of the palate and is followed by a considerable diastema. The remaining teeth are molariform and of transversely oval or subrect- angular shape ; a is the largest and - the smallest of the series, and the latter has on the posterior face a median vertical groove, which gives the grinding surface a reniform shape. All of the teeth are small in proportion to the size of the animal and the two series are nearly parallel. The skull has neither sagittal crest nor temporal ridges ; the rostrum is unusually long and has almost parallel sides and the preorbital fossse are very shallow ; the palate is but slightly convex between the molari- form teeth and less roughened than in the preceding genera, and ante- riorly is flat or even somewhat concave ; the premaxillae were evidently large, the facets for them upon the maxillaries being of uncommon size, while the median notch for the spines is a characteristically deep and narrow V. That Planops is very closely allied to Prepotherimn is clear ; indeed, more extensive material may perhaps show that the two are identical. On the other hand, the likeness to AnalcimorpJms is unmistakable and the latter genus connects the present group with the Megalonycliidce. The probable relationships between the Planopsidcc and the Megatheriidce can be most conveniently discussed in connection with Prepotherinni. EDENTATA OF THE SANTA CRUZ BEDS. 323 0 PLANOPS MAGNUS sp. nov. (Plate LVIII.) This species may be recognized by its very large size, for it is one of the largest known Santa Cruz Gravigrada, by the length of the rostrum, and by the more rectangular, less oval, shape of the upper molariform teeth. The type is a well-preserved skull (No. 15,346), lacking the premaxillae, jugals and mandible, which was found by Mr. Hatcher at Killik Aike. The caniniform (-1) is small, recurved, of longitudinally elliptical section, and with nearly horizontal masticating surface; a considerable space separates this tooth from -, but the distance in front of it, to the anterior edge of the palate, is more than twice as long as the diastema ; *• is trans- verse and molariform, longer antero-posteriorly than any of the other teeth and narrower transversely than any except -, and is of an irregu- larly quadrate shape ; - is broad and antero-posteriorly compressed and more nearly rectangular than any of the others ; - is like a, but slightly smaller and less regular ; A is much smaller and with reniform grinding surface, owing to the posterior vertical sulcus. MEASUREMENTS. Upper dentition, length 062 i, length 009 " 2-& 040 " width 012 Distance from J- to anterior edge of ^ length 009 maxillary 036 " width 014 Diastema between i and -2., length 017 -i, length 008 JT, length (t. e., antero-posterior diam- " width 013 eter) 008 & length 007 1, width (z. e., transverse diameter)- . . . .0063 " width Oi I In most of the Santa Cruz Gravigrada the highest point in the upper contour of the skull is the parietal eminence, which is in nearly the same vertical line as the glenoid cavity. In the present species, however, the upper contour is nearly straight, the rise from the occiput is very slight and the highest point is not in the parietal, but in the frontal zone, a little behind the orbits ; from the summit forward is a long and gradual descent. Except for the descending side walls of the posterior nares, the dorso-ventral diameter of the cranium is nearly uniform throughout, while that of the face diminishes anteriorly. Viewed from above and disregard- ing the zygomatic arches, this skull appears like an elongate, slightly 324 PATAGONIAN EXPEDITIONS : PALEONTOLOGY. irregular tube ; it is wide in the parietal zone, contracting gently to the postorbital constriction, thence gradually expanding again to the fore- head. No sagittal crest is present, merely a broad and obscurely marked sagittal area. The preorbital region, or rostrum, is unusually long and has nearly straight, parallel sides, though narrowing forward slightly ; the preorbital fossae are very shallow and hardly visible from above. The occiput is relatively high and has a distinct forward inclination ; the crest would appear not to have been prominent, though the loss of the supraoccipital leaves this somewhat uncertain ; the foramen magnum is transversely elliptical. The basioccipital is long and broad, strongly convex behind, almost flat in front ; from the foramen magnum a shallow median groove is continued for a short distance, a feature which has not been observed in any other species ; the condylar foramen is small and the foramen lacerum posterius is large. The low and wide exoccipitals do not meet in the median line, leaving between them a narrow space where the supraoccipital reaches the foramen magnum ; above the foramen the exoccipitals are produced almost as far as the hinder margin of the con- dyles, which are rather small ; the paroccipital processes are obsolete. The supraoccipital is lacking, but its shape is sufficiently indicated by the surrounding sutures ; it was very broad and shield-shaped, with a median ventral process, which, as already mentioned, extended between the exoc- cipitals to the foramen magnum ; it must have formed much the greater portion of the occipital surface, and dorsally was reflected forward for a short distance between the divergent parietals. The exposed portion of the periotic is a narrow vertical ridge, with a groove on each side of it, and ends ventrally in a roughened process. The tympanics have been lost, but the size of the fossae thus exposed apparently indicates that these bones were larger than in the other genera. In marked contrast to the smaller Gravigrada of the period, the parie- tals are, at least along the hinder border, very thick and filled with can- celli and small sinuses ; over most of their area these bones have a smooth, dense surface, and anteriorly they have short median processes between the frontals. So far as it is not covered by the pterygoids, the basisphenoid is broad and nearly plane, with a large tubercle at each pos- tero-internal angle, just behind the pterygoid suture. The presphenoid is concealed by the vomer, the median plate of which descends more gradu- ally and is not so conspicuous in the posterior nares as it is in P. longi- EDENTATA OF THE SANTA CRUZ BEDS. 325 restrains. The alisphenoid, though large, is almost -confined to the ven- tral aspect of the cranium, where it follows the course of the squamosal and has a short suture with the parietal and a longer one with the frontal ; the descending process is large and its ventral border is thickened and cancellous. The outer portion of the relatively large orbitosphenoid is depressed by two concavities leading respectively to the optic foramen and foramen lacerum anterius. The frontals are very large and have an inflated look, which indicates the presence of large sinuses ; the postorbital foramina are uncommonly large and conspicuous ; the sutures with the maxillaries are relatively long and straight, with a wide, shallow notch between them for the nasals. The squamosal is relatively small and forms no part of the occipital crest and has no connection with the exoccipital, from which it is separated by the periotic ; the broad, deep notch of the ventral border for the auditory meatus produces quite a distinct posttympanic process and the whole infero-lateral angle of the bone is rugose ; the glenoid cavity is but mod- erately concave, but extends farther upon the zygomatic process than in any of the other genera ; this process is short and rather slender and has a' distinct downward inclination. Although the jugal has been lost, its great length is demonstrated by the space between the zygomatic processes of the squamosal and maxillary. The lachrymal is of the ordinary type. The nasals have quite a characteristic form ; they are widest posteriorly, contracting forward to the narrowest part and thence broadening slightly to the anterior end ; along the median line, where the two nasals meet, is a narrow and shallow, but well defined groove ; at the forward end each nasal has a long lateral process, defined by a deep notch, while the median part is obliquely truncated, forming with its fellow a blunt point. The anterior nares are broad and low, with sides and top regularly curved and describing somewhat more than half of a transverse ellipse. The maxillary is very long, especially the preorbital portion, which is for the most part convex, the preorbital fossa being shallow and incon- spicuous and dying away dorsally. Owing to the narrowness of the nasals and the curvature of the maxillaries, the latter form more than half of the roof of the nasal chamber, and their anterior edge is thin, except at the infero-lateral angles where they are much thickened to form the facets for the premaxillae. The large and heavy zygomatic process is per- forated by a short infraorbital canal, the anterior opening of which is 326 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. double. The hard palate is long and narrow, with posterior convexity less marked than in the preceding genera, and the whole palate is less rugose and has far fewer vascular perforations than in the latter ; anteriorly, on each side of the median line and opposite the caniniform teeth, is a fora- men continued forward by a well defined groove almost to the border of the palate. The palatines contribute but little to the hard palate, ex- tending to a line opposite the middle of - and much narrowed by the broad alveolar processes of the maxillaries. The posterior nares do not extend so far forward as in most of the contemporary Gravigrada, the front margin being a little behind - ; the ventral border of the walls of the canal is thickened throughout. The short and narrow pterygoids are not entirely concealed by the alisphenoids, a narrow strip appearing externally behind the latter ; they end ventrally in tubercles which form projections on the inner side and hinder border of the narial canal. MEASUREMENTS. Skull, length in median basal line 189 Rostrum, width at preorbital fossae 046 " " condyle to anterior nares . .223 " " anterior end 041 Cranium, length condyle to edge of Distance, occipital condyle to glenoid orbit 153 cavity 03 5 Face, length orbit to anterior nares 071 Distance, occipital condyle to &- 093 Occiput, height 064 Zygomatic arch, length 119 " width at base 074 Palate, length in median line 078 Skull, width at postorbital constriction. .054 " width in front of 1 037 " " over lachrymals 084 " at ^ 023 Forehead, width 073 " " " &- 021 PLANOPS LONGIROSTRATUS Ameghino. (Plate LIX, Figs, i-i6.) Planops longiro stratus Amegh. ; Enumeracion sistematica, etc., 1887, p. 23. Schismotheritim intennixtum Mercerat, in part; Rev. del Museo de La Plata, T. II, 1891, p. 8. The skull in the Brown collection of the American Museum of Natural History agrees very well with the type of P. longirostratus in the La Plata Museum and also with the specimen which Ameghino has figured ('94°, 164, fig. 63), but is much better preserved than either; the parietals, occiput, basis cranii and mandible are lacking, but otherwise the skull is in an excellent state of preservation. EDENTATA OF THE SANTA CRUZ BEDS. 327 Compared with P. magnus, the most obvious characteristic of the pres- ent species is its very much smaller size, though there are numerous less striking differences in the teeth and skull structure. The upper canini- form is not placed quite so far behind the anterior border of the maxillary, and the diastema between - and - is also somewhat shorter proportion- ately ; - resembles the corresponding tooth of P. magnus, except in size ; a and A are rather more elliptical and less rectangular in shape and the long axis of each of these teeth is more oblique to the median line of the palate, inclining slightly forward, as well as externally ; * is somewhat the largest of the molariform series, though not much exceeding A in this respect; - is, as usual, reduced in size and, as in the preceding species, has a reniform grinding surface, with deep vertical groove on the posterior side. MEASUREMENTS. Upper dentition, length 048 i, length 0065 " " " 1-&. 032 " width 0085 Distance, 1 to anterior border of max- i, length 0065 illary 019 " width 0095 Diastema between -i- and %• oi I •*-, length 0055 J, length (t. e., antero-posterior diam- •" width 0093 eter) 006 £, length 005 5 1, width (t. e., transverse diameter) 0043 " width 007 In the skull the resemblance between the two species is very close, but, even disregarding size, there are a number of differences which appear to be characteristic and constant. In P. longirostratus the sagittal area upon the frontals is much narrower and the area and the temporal ridges are better defined. The top of the skull is more nearly horizontal and the descent to the rostrum is much more gradual ; the lachrymal is broader, but less prominent, and the foramen is smaller. The rostrum is shorter and wider and narrows more anteriorly, while the preorbital fossa:: are more distinct ; the nasals are shorter and wider and do not emarginate the frontals so deeply. MEASUREMENTS. Face, length orbit to anterior nares 045 Zygomatic arch, length 086 Skull, width at postorbital constriction .048 Palate, length in median line 053 " " " forehead 060 " width in front of ^ 03 1 over lachrymals 067 " at i 019 Rostrum, width at preorbital fossae 037 " " *• 019 " " " anterior end 030 328 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. Ameghino has referred two additional species to this genus, but the material is too fragmentary for satisfactory determination. The references are as follows. PLANOPS OBESUS Ameghino. Eucholceops infernalis Amegh., in part; Contrib. al Conoc. de los Mam. Fos. de la Repiib. Argent, 1889, PI. XXXIX, fig. 8. Planops obesus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 322. PLANOPS CYLINDRICUS Ameghino. Hapahps cilindricus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 318. Planops cylindricus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 164. PREPOTHERIUM Ameghino. (Plates LIX, Figs. 2, 2" ; LX, LXI.) Prepotherimn Amegh. ; Rev. Argent de Hist. Nat, T. I, 1891, p. 158. Eucholczops Lydekker, in part; Anales del Museo de La Plata, T. Ill, 1894, p. 95. It is a curious fact that, save for the teeth, little or no direct comparison can yet be made between this genus and Planops, because the parts that are known in the one are not yet known in the other. Much doubt there- fore remains as to the propriety of separating the two and, even admitting the validity of the distinction, we cannot yet be quite certain that all the species referred to Prepotherimn actually belong together. So far as may be judged from the extant material, the teeth are very constant in their character for the genus as a whole and for each of its constituent species and there is no such puzzling variability as occurs in the other two families of Santa Cruz Gravigrada. The two series of upper teeth, which in Planops are parallel, have a distinct convergence back- ward ; A is small, subcylindrical, horizontally abraded and followed by a considerable diastema ; the molariform teeth are well spaced apart, of elliptical form, very broad transversely and much compressed antero- posteriorly ; a is the largest of the series, while - and & diminish regularly in size. In the lower jaw, T is like the corresponding upper tooth, ^ and -5 are transversely elliptical, while 4 tends to a subcylindrical form. EDENTATA OF THE SANTA CRUZ BEDS. 329 Although the difference is not at all radical, no other contemporary genus has such teeth and they may be recognized at a glance. Hardly anything is known of the skull, merely the palate and most of the mandible ; the former resembles that of Planops in being nearly flat, but differs in a decided tendency to assume the triangular form. The mandible has a long and broad predental beak and the ventral border of the horizontal ramus, which in P. filholi is but moderately convex, in P. moyani is so much arched downward as to have a notable resemblance to the jaw of Megatherium. The skeleton is very imperfectly known and only in association with one species, P. potens, and will be described under the heading of that species. In brief, it may be said that the known parts of the skeleton generally agree quite well with the corre- sponding parts of the Santa Cruz Megalonychidce, but there are several significant differences, which are suggestive of a relationship with the Megatheriidcz. It can hardly be maintained, however, that any of the latter family were directly derived from any known species of Prepotherium. PREPOTHERIUM FILHOLI Ameghino. (Plate LIX, Figs. 2, 2".) Prepotheritim filholi Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 158. In addition to the type specimen in the Ameghino collection we have in the Brown collection of the American Museum of Natural History a right ramus mandibuli (No. 9,573), which appears to be referable to the present species. The upper caniniform, -, is small, erect, cylindrical and horizontally worn, and the molariform teeth are characterized by their transverse width and great antero-posterior compression ; the transverse crests are parallel, but the angles of the teeth are so rounded as to give the grinding surface a compressed oval, rather than a rectangular shape ; - and ^ are of nearly equal size, - and - progressively smaller. The lower dentition differs slightly from the upper ; T, which is implanted behind the end of the sym- physis and is followed by a short diastema, is small and very slightly com- pressed laterally ; * and ? are transversely oval, but less compressed antero- posteriorly than the upper teeth ; \ is also transverse, but with a tendency to the subcylindrical shape. 330 PATAGONIAN EXPEDITIONS : PAL/CONTOLOGY. The hard palate is nearly plane between the molariform teeth and has a low ridge along the median line of suture ; the backward convergence of the two dental series gives to the palate a characteristically triangular form. The mandible (Plate LIX, figs. 2, 2") evidently had a very elongate predental beak, though the anterior portion is so broken that the exact length is not determinable ; this elongation indicates a corresponding length of the rostrum and premaxillaries. From the portion preserved, it appears that this beak had nearly parallel sides, with flared and everted dorsal border, and probably the anterior end was much less pointed than in the Santa Cruz Megalonychida and may well have been as abruptly truncate as in Megatherium ; the symphysis is long and much less steeply inclined than in Hapalops and the chin is much more gradually rounded. The dentary portion of the horizontal ramus is short, of no unusually great depth and with only a moderately convex ventral border; in this respect there is a very striking difference from P. moyani, a difference which may be partly, though not entirely, due to the immature age of the specimen before us. Posteriorly also, the ramus is incomplete, but it is apparent that the coronoid process is relatively short and quite erect and that the angle is decidedly inflected ; the postero-external opening of the dental canal is at the base of the ascending ramus and is very narrow, hardly more than an oval slit. In the subjoined table the dimensions of the upper teeth and palate are from the type, those of the lower teeth and the mandible from No. 9,573, a younger and smaller animal. MEASUREMENTS. Upper dentition, length A-l. 046 Lower dentition, length ^_^ 029 1, length (*'. e., antero-posterior diame- T, length 008 ter) 0085 " width 006 " width (i. e., transverse diameter) 016 2, length 008 2-, length 0085 " width 0125 " width 0165 $, length 0075 •±, length 0085 " width on " width 013 ?, length 0085 i, length 006 " width on " width 0105 Mandible, depth at ^ 035 Palate, width at ^- 020 " thickness at ^ 0185 " " & 013 estimated length of beak. . . .050 Lower dentition, length 043 EDENTATA OF THE SANTA CRUZ BEDS. 33! PREPOTHERIUM MOYANI Ameghino. (Plate LX, Figs, i, i°.) Prepotherium moyani Amegh. ; £num. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 162. This species, which is as yet known only from the type, is of nearly the same size as the preceding one, but differs in the form of the teeth and the character of the mandible. The molariform teeth have a more oval grinding surface than in P. filholi, with the transverse crests more curved and less parallel, while the antero-posterior compression is much less ex- treme ; another distinction is that - is larger than -, while in the preceding species - and - are of almost equal size ; - has a deep vertical groove on the posterior side, producing a reniform grinding surface, as in both of the species of Planops. Unfortunately, the mandible is far from complete, but the portion pre- served is highly characteristic ; the peculiarity consists in the very great vertical depth of the horizontal ramus in the dentary region, with ex- tremely convex ventral border, which rises steeply behind and becomes concave below the ascending ramus ; anteriorly, the rise is very gradual, much more so than in P. filholi, and indicates a very long predental beak. The animal appears to have been fully adult and yet the jaw has on its outer side a large number of minute vascular foramina, producing a surface texture unlike that of any other contemporary species. The ex- ternal dental foramen has a slightly lower position than in P. filholi and is considerably larger, especially in width. The resemblance of this mandible to that of Megatherium is very strik- ing and suggests that the ancestor of the latter was allied to the present species. MEASUREMENTS. Upper dentition, length 060 T, length 007 " " " 1-A 042 " width 006 1, length (i. e., antero-posterior diam- ^, length 0095 eter) 009 " width 0135 " width (i. e., transverse diameter) . . . .007 ^, length 009 £, length 0085 " width 0145 " width 0115 f, length 0105 3-, length 0095 " width 014 " width 014 Mandible, depth below -g 046 Lower dentition, length 050 " " " ¥ 040 " M 036 332 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. PREPOTHERIUM POTENS Ameghino. (Plates LX, Figs. 4-8 ; LXI.) Prepotherium potens Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, P- 325- Eucholczops titan Lydekker; Anales del Museo de La Plata, T. Ill, 1894, p. 98. This is much the largest known edentate of the Santa Cruz epoch and is the commonest representative of the genus, though all of the specimens yet obtained are lamentably imperfect and almost nothing is known of the skull. In the Princeton collection are a number of individuals which enable me to describe a considerable part of the skeleton, especially when supplemented by the material in the Ameghino collection. Ameghino has described the teeth as follows: "The last upper molar has a deep vertical groove on the posterior face ; diameter of m -, antero- posterior 9 mm., transverse 16.5 mm. ; of - 6.5 x 12 mm." ('91, 325). "The upper caniniform has a diameter of 9 mm. ; the diastema is 1 1 mm. long ; the interdentary region of the palate between the caniniforms is 25 mm. wide. The lower caniniform has a diameter of 7 mm. and the diastema which follows it is 8 mm. long; the first upper molar has an antero- posterior diameter of 10 and a transverse diameter of 15 mm. ; the last lower molar has an antero-posterior diameter of 12 and a transverse diameter of 15 mm. ; length of lower dentition 70 mm. ; height of mandi- ble below penultimate molar 55 mm." ('94", 163-4). The Princeton col- lection contains only two loose teeth associated with No. 15,521 ; one of these, which may be the third upper tooth, measures ii-5x 18 mm., and the other, which appears to be the second lower tooth, measures 9.5 x 13.5 mm. As appears from the measurements, the teeth are very much compressed antero-posteriorly. The parts of the skeleton represented by the various individuals are ten thoracic, four lumbar and three caudal vertebae, and most of the sacrum ; two segments of the mesosternum and several ribs ; incomplete humerus, ulna and radius, and much of the manus ; the greater part of the pelvis, femur and tibia complete, and fibula nearly so, while the astragalus and calcaneum are in the Ameghino collection. Although the vertebral formula is not known, it is evident that the number of vertebrae was large, as is indicated by the great differences of EDENTATA OF THE SANTA CRUZ BEDS. 333 size and form in the various parts of the thorax. The individual vertebrae resemble those of Hapalops, though on a much larger scale and with several characteristic modifications. Compared with the vertebrae in the hinder part of the thorax, the first thoracic is very small and shows that the neck was probably more slender than in Hapalops ; the centrum is short, broad, much depressed, with feebly convex, D-shaped anterior face, and with two parallel, widely separated, thick and very prominent ventral keels, which do not occur in any of the preceding genera ; the anterior facets for the rib-heads are large, slightly concave, and placed partly on the centrum and partly on the neural arch, while the small posterior facets project quite prominently from the postero-lateral angles of the centrum. The transverse process is very prominent and heavy and has a large facet for the tubercle of the first rib ; the prezygapophyses are lateral in position, concave, very heavy and prominent, while the postzygapophyses are small, convex and placed on the neural arch. The next vertebra of the series is one which corresponds in form to the tenth or eleventh thoracic of Hapalops (Plate LX, fig. 4) ; the cen- trum is relatively small and of quite a different shape from the first, hav- ing subtriangular faces and nearly equal transverse and dorso-ventral diameters ; the neural canal is remarkably large, its diameters exceeding those of the centrum ; the pedicles of the neural arch are high and narrow, the arch and spine extending far behind them; the spine is relatively short and slender and has a very strong backward inclination ; the trans- verse process is shorter than on the first vertebra, but very prominent and heavy. Behind the middle of the thorax the centra increase steadily in size, but the gradual way in which this increase is effected is strong evidence that the backbone was nearly or quite as elongate as in Hapalops. In the posterior part of the region the vertebrae are exceedingly large and have assumed the appearance of lumbars ; the centra are massive, short, broad and thick, with subquadrate faces ; the ventral foramina are nearly obsolete ; on the last two vertebrae, at least, there are no facets for the tubercles of the ribs ; the neural spines are shorter than in the middle of the thorax, and less inclined, but they are very heavy and much thick- ened at the free end ; the transverse processes are very short, broad, sharply upcurved, and heavy and rugose at the distal end. The mode of articulation of these vertebrae is almost the same as in Hapalops, but the 334 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. large size of the processes gives them a very complex appearance. Very large and concave prezygapophyses rise prominently above the neural arch, while the rugose metapophyses are shorter and heavier than in Hapalops; the accessory prezygapophyses are prominent, shelf-like pro- jections below and external to the primary pair; the articular surface is not plane, as it is in Hapalops, but concave, and is reflected upward upon the external side of the primary pair, an incipient stage in the development of the second accessory pair of articulations. The postzgapophyses are convex semicylinders, separated from the transverse processes by deep, nar- row notches ; the accessory surfaces are on the transverse processes and chiefly on the ventral side, but partly reflected upon the dorsal side also. Four lumbars are associated with one individual, but only the third is sufficiently well preserved to show the mode of articulation (Plate LX, figs. 5-5*). In all of the lumbars the centra are of about the same length, but become broader and more depressed posteriorly, especially the hinder faces; the third and fourth have short and blunt, but quite prominent projections from the infero-lateral angles of the posterior faces ; except in the first, in which they are obsolete, the ventral foramina are very large, and the opening in the floor of the neural canal is extraordi- narily large in the second vertebra. The neural spines differ from those of the hinder part of the thorax in being longer vertically, narrower antero- posteriorly, but much thicker and more erect ; the successive spines appear to have been nearly or quite in contact. The zygapophyses, at least of the third lumbar, have an additional complication, as compared with those of the posterior thoracic region, namely, that the accessory articular pro- cesses are each divided into two, one dorsal and one ventral, the only instance of the kind known among the Santa Cruz Gravigrada. What remains of the transverse processes shows that they were long, broad and depressed. The number of sacral vertebrae can hardly have been less than five and may have been six. The first vertebra has a very broad and depressed centrum, thinning backward into a mere plate ; all the other centra are of similar plate-like form, except the last, which has a large posterior face ; the penultimate sacral has a pair of low, parallel, infero-lateral keels, which on the last become quite prominent and are separated by grooves from the chevron facets ; very small ventral foramina appear on the first and last vertebrae. Posteriorly, at least, the neural canal is relatively larger than in EDENTATA OF THE SANTA CRUZ BEDS. 335 Hapalops and of a different shape, owing to its greater height ; the ridge formed by the coalesced spines is high and has a much thickened free border. Only on the last two vertebrae are the transverse processes preserved ; here, they are long and very heavy and are completely fused with the ischia, beyond which the distal ends project as short and massive protuberances. Although of a similar type to those of the contemporary Megalonyc hides, the caudal vertebrae have a decided resemblance to those of Megatherium, especially in their massiveness. The first caudal (Plate LX, fig. 6) has a short, very heavy, block-like centrum, with two pairs of chevron-facets, of which the anterior pair is the smaller, though far better developed than in any of the preceding genera ; in the latter a vascular groove on each side leads around the side of the centrum and behind the transverse process into the neural canal ; in the present species the ventral portion of this groove is converted into a canal, forming a conspicuous foramen at the base of the transverse process, and another external to the pos- terior chevron-facet. The neural canal is very large, far higher than in Hapalops, and the pedicles of the arch are much more massive, as is also the short spine ; the zygapophyses are remarkably heavy and there are no distinct metapophyses. The transverse processes are relatively somewhat shorter than in Hapalops and extend more obliquely backward, but are very much heavier and more expanded at the distal end. Other caudal vertebras preserved are the second, the ? sixth and part of the ? tenth ; in all the centrum remains of nearly the same length, but with diminishing diameters, and the anterior pair of chevron-facets are much smaller than the posterior pair and quite widely separated from them ; the processes diminish in the usual gradual manner, but their remark- able heaviness is characteristic of them throughout. In the ? sixth the transverse processes are much shorter and thinner than in the first or second, but are broader, especially at the distal end. Apparently, the tail in the present species was decidedly heavier than in the Santa Cruz Megalonychidce, but relatively somewhat longer and more slender than in Megatherium. The ribs are broader than in any of the preceding genera, approximating the proportions of Megatherium and Mylodon. The first rib is very short, but with a decided lateral curvature, making the inner border strongly con- cave ; the broad side is turned forward and the outer border is quite thick ; the neck is long and slender, projecting inward almost at right angles 33^ PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. with the principal axis of the rib ; the head bears a single circular and nearly plane facet which presents backward and articulates with the first thoracic ; apparently there was no articulation with the seventh cervical ; the tubercle rises prominently above the neck, bearing a large saddle- shaped facet. Distally, the rib is expanded and rugose and has a large facet for the manubrium ; though no suture is apparent, this portion is doubtless the coossified sternal rib. What is believed to be the second rib has an even longer and more slender neck than the first ; the facets on the head for the first and second thoracics are nowhere in contact, but separated by a narrow sulcus ; the tubercle is smaller and lower than on the first ; the shaft is the slenderest of all the ribs preserved, but, as in the first, the principal diameter is transverse. However, this rib forms the transition from the first to the succeeding ones, in which the antero-pos- terior diameter greatly exceeds the transverse and which are very broad and plate-like. In those ribs which articulate with two vertebrae the two facets of the head are entirely separate ; passing backward, we find that the anterior facet is steadily reduced, until it disappears altogether, while the posterior is increased, finally covering the head. Throughout the series the neck is long, though broader and more depressed than in the first and second, and curving uninterruptedly into the shaft, not forming an angle with it. In the "true ribs " the distal end is somewhat expanded in both dimensions and bears a large, convex facet for the sternal rib, while in the "false ribs" the distal end is a very rough surface. A single distal end of a sternal rib is preserved, which fits accurately the second and third segments of the mesosternum and bears a curiously close resemblance to the proximal end of a vertebral rib. The fragment is, in general, very similar to the corresponding bone of Mylodon, yet differs in a number of particulars ; it is more compressed antero-posteriorly, thicker dorso-ventrally ; the facets on the " head " for the ventral part of the sternal segments are separate, while the much smaller facets for the body of the sternal segments are confluent. Of the sternum have been found two mesosternal segments (Plate LX, figs, 7, 7") which are of exactly the same type as in Hapalops and agree quite well with the second and third segments of Mylodon. It would be superfluous to give a description of these bones, which differ from those of Hapalops merely in size. EDENTATA OF THE SANTA CRUZ BEDS. 337 First thoracic, length of centrum " " width of anterior face. . height " " " width over transverse processes ? Eleventh thoracic, length of centrum . " " width of anterior face " height of anterior face " " width of posterior face " " height " . " length of spine . . . Penult, thoracic, length of centrum . . . width of posterior face height of " " " width over transverse processes Last thoracic, length of centrum " " width of posterior face .. " " height of posterior face. " " width over transverse processes " " height " " length of spine " " width of spine at end . . . First lumbar, length of centrum width of posterior face . . height of posterior face . . Second lumbar, length of centrum. . . . " " width of posterior face . " " height of posterior face height Third lumbar, length of centrum " " width of posterior face . . height of " " . . height length of spine " " width " " at end. . Fourth lumbar, length of centrum. . . . " " width of posterior face, height of " MEASUREMENTS. .029 Fourth lumbar, height .032 " " length of spine .0185 " " width of spine at end . First caudal, length of centrum .090 " " width of anterior face . . . .03 1 " " height width over transverse .0285 processes Second caudal, length of centrum. . . . .026 " " width of anterior face. " height .035 " " width over transverse .095 processes .045 ? Sixth caudal, length of centrum .039 " " width of anterior face .. .041 " " height .038 " " width over transverse processes .083 ? Eleventh caudal, length of centrum . . .040 First sacral, width of anterior face. . . . .043 " " height " " " .039 Last " width " posterior face . . . " " height " " "... ? Second mesost. segment, length " " " width of an- .084 .121 .049 .042 •043 .049 .036 •043 .042 •039 .127 .044 •053 •034 .127 .058 .038 .044 •053 .031 terior face . . width of pos- terior face . . " " " length ofpro- cess " " width of pro- cess " " " height ? Third mesost. segment, length " " " width of an- terior face . . width of pos- terior face . . " " " length of pro- cess " " " width of pro- cess " " " height .127 .065 •035 •034 .043 .086 .130 •034 .040 .080 .116 .032 .036 .057 .086 •034 .057 .031 .045 .029 .032 .025 .029 .021 .024 .027 .029 .0305 .0305 .016 .026 ,029 338 PATAGONIAN EXPEDITIONS'. PALAEONTOLOGY. Although none of the fore-limb bones is complete, they are all so nearly so that a close approximation of their length may be obtained. With many resemblances to those of the contemporary Megalonychidcz, these bones have also a suggestive likeness to those of Megatherium, especially in their length and slenderness as compared with those of the hind-limb. The following table will show the very marked contrast between the present species and Hapalops longiceps in this respect, and the likeness of the former to Megatherium. In each species the length of the femur is taken as 100 and the other bones are calculated in percentages of that length. MEASUREMENTS. Hapalops longiceps. P. potens. Megatherium. Femur 100 100 100 Humerus 90.3 103.6 105.3 Radius 80. 1 101.6 94.6 Ulna 92.9 1 1 5.4 106.6 Tibia 9.17 81.1 84 The humerus displays a general likeness to that of Hapalops, with a number of minor differences; the tuberosities are much larger than in Megatherium and as prominent as in Hapalops, though of more equal size, the external one being larger and the internal one smaller. The shaft is proximally broad and antero-posteriorly compressed, narrowing downward to a point just above the distal expansion ; the deltoid area is less prominent than in the large species of the latter, but far longer, extending down the shaft below the level of the epicondylar foramen, where it abruptly terminates ; the epicondylar foramen is covered by an unusually narrow bridge and from the course of this bridge it may be inferred that the epicondyle was less developed than in Hapalops. No part of the supinator ridge remains, but enough of the shaft is preserved to show that the ridge had no such proximal extension as in the last named genus. The humerus of Megatherium is very characteristic in appearance, which is chiefly due to the great reduction of the tuberosities and deltoid area, the slender, cylindrical proximal part of the shaft, the immense breadth distally, and the loss of the epicondylar foramen. The radius resembles that of Megatherium in shape and in its remark- able elongation, being, in fact, longer in relation to both the humerus and the femur; the head is discoidal, not transversely oval, as it is in the EDENTATA OF THE SANTA CRUZ BEDS. 339 Santa Cruz Megalonychidce, and simply concave ; the proximal facet for the ulna is very small, not covering one third of the circumference of the head, but quite extended proximo-distally. The proximal portion of the shaft is compressed antero-posteriorly, much more than in Hapalops, and the abrupt broadening, which in the latter occurs nearly in the middle of the shaft, is very much nearer to the proximal end ; the bicipital tubercle is very prominent and rugose. As a whole, the shaft is curved both laterally^and anteriorly and quite closely resembles that of Megatherium, while the suprastyloid tubercle is much less prominent than in the latter; the carpal surface is narrower internally and less extended upon the styloid process. The ulna is very like that of Hapalops. In Megatherium the olecranon is remarkably short and broad and inclined backward from the plane of the shaft, making the whole proximal end extremely massive, while the distal end of the ulna is narrow, very thick and incurved. In Prepothe- rium, on the other hand, the ulna differs from that of Hapalops merely in its straightness and relative length. The manus (Plate LXI, fig. 3) is incompletely known, but the parts preserved differ in many ways from the corresponding elements of the Santa Cruz Megalonychidce, without displaying any very marked approxi- mation to those of Megatherium. Of the carpus, only the trapezoid and magnum have been identified ; the former is longer proximo-distally than in Hapalops ; the dorsal face is broad, but toward the palmar side the bone contracts almost to an edge ; the scaphoid facet is not regularly saddle-shaped, but divided into two parts, the junction of which forms a low ridge ; the distal facet for metacarpal II is similarly divided and on the radial side extends almost to the scaphoid surface. Evidently, the trapezoid had a more oblique position in the carpus than that of Hapalops. The magnum is very different from that of the latter genus, the proximal end rising toward the palmar side into a prominent head, almost as in an ungulate, and the proximo-internal border is not produced upward between the scaphoid and lunar, the lunar facet covers nearly the whole proximal end, making the contact with the scaphoid more lateral than proximal. On the distal end, the dorsal portion of the facet for metacar- pal III is in two parts which meet nearly at a right angle ; the palmar half is single, large and concave ; dorsally, the magnum has no contact with metacarpal II, but the palmar extension overlaps the head of the latter. 34-O PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. It may be asserted with confidence that the manus was pentadactyl and that all the digits carried claws. Metacarpal I is short and very heavy and has a rugged, massive appearance, quite unlike the smooth, subcylin- drical form seen in Hapalops ; the facet for the trapezium is very large and oblique, forming a sharp edge with the facet for metacarpal -II ; the shaft is short, heavy and rugose ; the distal trochlea is well developed and has a distinct carina. Metacarpal II is very much longer, but relatively slender ; the proximal end has a curiously warped surface for the trapezoid ; dorsally there is no contact with the magnum, but on the palmar side there is an articulation of considerable extent ; on the radial side of the head is a very large and slightly concave facet for the first metacarpal, and on the ulnar side a still larger facet for the third. The shaft is of very irregularly trihedral shape, increasing in diameter distally ; it receives a somewhat twisted appearance from the presence of a prominent, oblique rugosity upon the dorsal face and from the obliquity of the carina ; on the ulnar side, below the facet for III is a prominent rugosity, which may represent an incipient stage of the extensive connection between the second and third meta- carpals, which characterizes Megatherium. The distal trochlea resembles that of Hapalops, except for the obliquity of the carina and the narrow- ness of the lateral facets. Of metacarpal III only the distal end is preserved ; the broken end of the shaft has an almost square section, of a diameter much exceeding that of metacarpal II. The carina is less extended palmo-dorsally and pro- jects less in front of and behind the shaft than in Hapalops, and its free border is much less curved. Metacarpal IV much exceeds II in length, though not nearly so much as in Megatherium; the proximal end must have been extensively over- lapped by III, the facet for which is much -more oblique than in Hapalops, leaving but a narrow surface for the unciform, while the facet for V resembles that in the latter genus, and there was evidently no such artic- ulation between metacarpals III, IV and V, as in Megatherium. The shaft is much compressed laterally, but thick palmo-dorsally, the dorsal face being a narrow ridge. The trochlea is quite different from that of Hapalops, the carina being less prominent and having a straighter edge, while on the palmar side are small, but well defined and prominent facets, probably for the sesamoids. EDENTATA OF THE SANTA CRUZ BEDS. 341 Aside from the unguals, the phalanges do not differ markedly from those of Hapalops and have little resemblance to the highly specialized phalanges of Megatherium. The first phalanx of digit I is elongate and slender ; the proximal trochlea is moderately grooved and deeply notched on the palmar border for the metacarpal carina, and the distal trochlea is also grooved and somewhat asymmetrical. In the second digit this phalanx is much like that of Hapalops in shape, but is relatively a little longer and its proximal end is somewhat less deeply grooved. The second phalanx of digit II differs but slightly from that of Hapalops, except in being a little shorter; the proximal trochlea is less deeply con- cave and its median dorsal portion does not form so prominent a beak; the distal trochlea has a shallower median groove and is invaded in the median dorsal line by a broad, shallow sulcus, which is not present in Hapalops, but there is no such fossa on the dorsum of the shaft, for the beak of the ungual, as appears in that genus. In digit III the second phalanx is shorter but much stouter than in digit II ; it differs consider- ably in form from that of Hapalops, the median ridge and dorsal beak of the proximal trochlea are much less pronounced, and the phalanx is not constricted palmo-dorsally below the proximal trochlea ; the distal trochlea has a shallower median groove. The unguals are very different from any known Santa Cruz genus of the MegalonychidcB and have considerable likeness to those of Mylodon. Compared with that of Hapalops, the ungual of digit II is very long, broad and low ; its dorso-palmar diameter is much less and consequently the dorsal surface is much less strongly arched, while the ventral surface is more so ; the proximal trochlea is broader and less concave and has a far less prominent intercondylar ridge ; the subungual process is extremely large and heavy ; the distal end is bluntly rounded and the cleft becomes a very shallow dorsal groove. In the pollex the ungual is similar, but very much shorter and less depressed. In the following table the lengths of the fore-limb bones are only ap- proximate, but the error must be slight. MEASUREMENTS. Humerus, length 309 Radius, proximal width 035 " proximal width 090 " " thickness 033 thickness 063 " distal width 052 Radius, length 303 " " thickness 038 342 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. MEASUREMENTS. Ulna, length 344 " " of olecranon 062 " width at sigmoid notch 056 " distal width 020 " " thickness 019 Metacarpal I, length 038 " " proximal width 022 " " distal width 017 Metacarpal II, length 064 " " proximal width 023 " " distal width 027 Metacarpal III, distal width 026 Metacarpal IV, length 089 Metacarpal IV, proximal width 028 " " distal width 025 Phalanx i, digit I, length 030 " " " " proximal width 018 Phalanx I, digit II, length. 028 " " " " proximal width ... .025 Phalanx 2, digit II, length 047 " " " " proximal width ... .021 Phalanx 2, digit III, length 043 " " " " proximal width ... .026 Ungual, digit I, length 045 Ungual, digit III, length 085 " " " proximal width 023 The pelvis is represented by imperfect specimens, which give no infor- mation upon certain important questions, yet are sufficiently complete to show a number of significant differences from the pelvis of Hapalops. The ilium has an even shorter peduncle than in the latter ; its anterior end is somewhat more expanded and everted and has a more definite and thickened crista. The dorsal portion of the ischium is less horizontal and extends upward as a broad, thin plate, which is ankylosed with the trans- verse processes of the last two sacral vertebrae ; the tuberosity is not very large, yet more prominent than in Hapalops; the descending portion is very long, quite broad and very thin, making the obturator foramen large, with dorso-ventral diameter much exceeding the antero-posterior, and giving the posterior pelvic opening a remarkably large dorso-ventral diameter. The pubis is long and very slender, except distally, where it expands to take part in the symphysis, which is quite elongate. The resemblance of this pelvis to that of Megatherium is quite distinct. The femur (text-figure 25", p. 1 73 ; Plate LX, fig. 8) is remarkable for its great breadth and antero-posterior compression ; its general appear- ance and proportions are quite like those of Megalonyx, but there are certain suggestive similarities to Megatherium. The hemispherical head is very large, and the large pit for the round ligament, which is on the posterior side, is entirely enclosed in the articular surface; the neck is longer than in Megatherium and the bridge from head to great trochanter is longer and has a more concave border. The great trochanter is very large and massive and encloses a considerable digital fossa; the second trochanter differs from that of the Pleistocene genera in being a prominent, EDENTATA OF THE SANTA CRUZ BEDS. 343 bluntly conical tubercle and not a roughened ridge ; the third trochanter is much less prominent than in the Santa Cruz Megalonychidce and of quite a different shape ; it does not, as in Hapalops, rise abruptly from the shaft, but forms a long, gentle convexity, the middle part of which is thickened and rugose and represents the trochanter proper, much as in Megalonyx, though larger. The shaft is very broad and antero-posteriorly compressed ; the anterior face is convex transversely, slightly concave longitudinally, and its proximal half has parallel ridges for muscular attachment, as in the Pleistocene genera ; on the hinder face a low, but distinct, ridge runs obliquely from the great trochanter to the inner side of the shaft, somewhat below the middle. The external tuberosity is very prominent, more so than in Megalonyx, but less than in Megatherium, while the internal is even larger than in the latter. The distal articular surfaces have a significant likeness to those of Meg- atherhtm, though they are much less specialized ; the condyles are of more nearly equal size and not so widely separated ; the external condyle is less reduced, especially in width ; the rotular trochlea is broader and less con- cave transversely, and is connected with both condyles, but in a very sig- nificant way. In Megalonyx the external condyle is separated from the trochlea and the inner condyle is connected with it " only by a narrow, isthmus-like prolongation " (Leidy, '55, 38) but the articular surfaces are not continuous, which led Owen to suggest that in this genus the knee- joint had three synovial capsules ('60, 813). In Hapalops the articular surfaces of both condyles are continuous with the trochlea, but the Mega- lonyx type is present in an incipient degree, the connection being much narrowed by an extension of the intercondylar notch on both sides. In Megatherium the external condyle is broadly continuous with the trochlea, but the internal condyle is widely separated from the latter. As regards the distal end of the femur, Prepotherimn stands in the same relation to Megatherium as Hapalops does to Megalonyx ; both condyles are con- nected with the trochlea, but, while the external one is broadly so con- nected, the internal is united with the trochlea by a very narrow bridge. The tibia (Plate LXI, figs. 2, 2") is not very different from that of Hapa- lops, but its differences are in the direction of Megatherium. The proximal end is broad, very heavy and somewhat compressed antero-posteriorly; the condyles are more equal than in Hapalops and the spine is less promi- nent ; the cnemial process is a massive transverse ridge, which is not ex- '344 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. tended down the shaft and projects very little. The shaft is broad, antero- posteriorly compressed, and contracts from the proximal end, expanding again at the distal end. The astragalar surface is quite different from that of Hapalops, being much more distinctly divided into two facets by an intercondylar ridge and by a short, deep sulcus from the dorsal border ; the inner facet is much more concave, the outer one very shallow ; the internal malleolus is much less reduced, the deeply grooved process which arises from the inner side, behind the malleolus, is decidedly less prominent. The fibula, which has lost the proximal end, has a stout, trihedral shaft, somewhat compressed laterally, and with a rugged linea aspera along the postero-internal border. The distal end forms a very massive external malleolus, which is not unlike that of Megatherium, but extends much farther below the level of the tibia. Little is known of the pes. The astragalus (Plate LX, fig. 2) differs in a marked way from that of all the contemporary Megalonychidcz, and especi- ally in relative shortness and width, in the deeper grooving of the trochlea, and in the incipient transformation of the inner condyle into the odontoid shape seen in Megatherium. The calcaneum has a broad, depressed, plate-like tuber, not unlike that of the Megalonychidce, but the sustentaculum is much more prominent and its astragalar facet presents dorsally, at right angles to the cuboid facet, instead of being almost parallel with it. The facet for the cuboid is remarkably narrow planto-dorsally, and below it is a thickened, callus- like mass of bone. The ungual phalanges of the pes are less different from those of Hap- alops than are the unguals of the manus ; being shorter, more curved and compressed and more sharply pointed than the latter. MEASUREMENTS. Femur, length from head 298 Tibia, distal thickness 040 " " " great trochanter .. .310 Fibula, estimated length 218 " proximal width 131 " width of shaft 017 " distal width 104 " thickness of shaft 02 1 Tibia, length 230 " distal width 042 " proximal width 104 " thickness 049 " " thickness 071 Ilium, length 162 " distal width 079 " greatest width 205 EDENTATA OF THE SANTA CRUZ BEDS. 345 MYLODONTID^E. In the Santa Cruz beds the representatives of this family are rare and most of the specimens are more or less fragmentary, so that our knowl- edge of these forms is still very incomplete. Except the skull, nothing is positively known concerning the skeletal structure of the Santa Cruz members of the family, but a few isolated vertebrae, limb and foot-bones have been found, which may, with great probability, be referred to it. The family is most distinctively characterized by the teeth, which in the upper jaw are triangular, and in the lower jaw lozenge-shaped, while the last lower tooth is bilobate; the valleys are central and are usually enclosed in a continuous wall of the harder dentine. The teeth of each jaw are in continuous series and without diastema, and -1 is always implanted very far behind the anterior end of the maxillary. The forms of the teeth are subject to great variation, not infrequently differing on the two sides of the same jaw, and no two specimens are quite alike ; slightly different modes of wear, which are doubtless individual, often give a very different appearance to the teeth. In general appearance and proportions the skull is very similar to that of the Santa Cruz Megalonychida, though with a number of constant differences. The occipital crest is but slightly developed and the sagittal crest apparently not at all ; the cranium is rounded and smooth, not flat- ened on top, as it is in Mylodon, nor having a narrow sagittal area, such as occurs in Scelidotherium. The parietals seem to have no sinuses and those of the frontals are very small ; owing to the lower occiput and shallower facial region, the upper contour of the skull has a much more decided antero-posterior curvature than in either of the Pleistocene genera. The lachrymal has the same prominent, mammillary shape and funnel-like foramen as in the other two families. The face is elongate and very slender, and the rostrum may have parallel sides, or it may broaden anteriorly, though never so strongly as in Mylodon. The mandible differs in a number of details from that of the other two families ; the horizontal ramus has a nearly straight ventral border ; the predental beak is long and deeply concave and has nearly parallel sides, with rounded or bluntly pointed anterior end. The condyle is placed upon a shorter neck than in the contemporary Megalony chides, but is raised higher above the level of the teeth, making the sigmoid notch 346 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. shallower; the coronoid process is broader and less recurved and does not rise so high above the condyle ; the angular process is shorter, but much broader dorso-ventrally, and thus the whole hinder portion of the jaw has a characteristic appearance. The postero-external opening of the dental canal is on the horizontal ramus below the base of the coronoid, and there is a single large and conspicuous mental foramen on each side of the predental beak, near the dorsal border. The few known vertebrae differ but little from those of Hapalops. The limb-bones are short and heavy and the humerus, at least, has a decided resemblance to that of Mylodon, as is also true of the first metacarpal. The astragalus is characteristically different from that of either of the preceding families ; it has much the same narrow, elongate shape as in the Megalonychidce, but the inner condyle has already begun to assume the odontoid form and suggests that of Mylodon. On account of the rarity and incompleteness of the material, the tax- onomic subdivision of this family is an even more difficult task than in the case of the Megalonychidce, and the difficulty is increased by the great variability in the forms of the teeth. Indeed no satisfactory arrangement is yet possible and the scheme here adopted is merely provisional. Ameghino has named four genera and nine species, but this seems to be an unnecessarily large number, and is almost equivalent to making a different species for every individual. NEMATHERIUM Ameghino. (Plates LXII ; LXIII, Figs. 2-8.) Nematherium Amegh. ; Enum. Sistem. etc., 1887, p. 22. Ammotherium Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 321. Lymodon Amegh. ; Ibid., p. 324. The principal characteristic of this genus is the decided anterior diver- gence of the two dental series, which is displayed in both upper and lower jaws, and the consequent broadening of the palate forward, though it never approximates the condition seen in Mylodon. Within certain limits, the teeth vary much in shape ; - is usually cylindrical, though it may be triangular, and, in most instances, is bevelled by abrasion, but may be horizontally worn ; the other upper teeth are triangular, varying much in proportions and in mode of wear ; -, * and - are usually bevelled, EDENTATA OF THE SANTA CRUZ BEDS. 347 but in some specimens they are almost horizontally abraded ; * or A is the largest of the series and - the smallest and least distinctly triangular. Even more variable are the lower teeth ; T is somewhat elongate antero- posteriorly, laterally compressed and" of either triangular, or oval section, and usually with bevelled crown ; in several instances - has worn a deep, step-like notch on the posterior side of T; Y and ¥ are four-sided and lozenge-shaped, with the long axis of the crown oblique to the line of the jaw ; T is bilobate and very elongate antero-posteriorly ; the anterior lobe is transverse, but somewhat oblique, while the posterior lobe has a fore-and- aft direction, curving inward at the hinder end, and is convex externally and, except in one specimen, concave internally. Aside from mandibles, the skull is known only from three specimens in the Ameghino collection, one of which, the type of Ammotherium acitleatum (Plate LXII, figs. 2, 2«, 2<£) is quite complete and has the mandible, lacking the ascending ramus ; another, the type of Lymodon perfectus (Plate LXII, figs, i, \a] is the right half of a skull, without lower jaw ; the third, the type of N. longirostris, is very incomplete. The same collection contains also two palates, with teeth, referred respectively to Ammotherium declivum and A. profundattim, but these add little to our knowledge of the skull structure in the genus. In proportions this skull does not differ at all radically from that of the Santa Cruz Megalonyc hides, the most striking distinction being the length and slenderness of the region in front of the brain-case. The occiput is broad, quite low, and inclined slightly forward ; the condyles are widely separated by a broad ventral notch and the paroccipital processes seem to be obsolete ; the occipital crest is inconspicuous and the supraoccipital is reflected well over upon the dorsal side of the cranium. The brain-case is full and rounded, without sagittal crest or area, narrowing regularly forward to the interorbital region ; the zygomatic arch is imperfectly known, but seems not to have been unlike that of Hapalops. The post- orbital constriction is very shallow and inconspicuous and hence the long frontals have little of the hour-glass shape seen in the Megalonychidce, and the sinuses produce no noticeable elevation of the forehead. In front of the postorbital constriction the skull is remarkably slender and elongate, one of the most characteristic differences from the two preceding families ; the maxillaries are produced far in front of the first tooth and the pre- orbital fossae are very shallow, forming no distinct constriction when the 348 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. skull is viewed from above or below ; the maxillaries end abruptly at the anterior nares and have no such forward prolongation as do those of Scelidotheriuni. Posteriorly, the palate, which extends a short distance behind the last tooth, is very narrow and quite decidedly convex, broad- ening and flattening anteriorly between the divergent rows of teeth ; at the front border is a narrow and deep V-shaped notch for the premaxillary spines ; the facet for the external branch of the premaxillary is similar in shape and position to that of Hapahps. Of the premaxillae only the spines are known, but from the shape of the anterior ends of the maxillaries, the facets upon them, and from the predental beak of the mandible, the shape and size of these bones may be approximately determined. In all probability, the premaxillae of Nenia- therium were, like those of Mylodon, each composed of two branches, one internal, or the spine, and the other external, but having no distinct anterior branch, such as is found in the Santa Cruz Megalonychidcc ; they were more elongate than in Mylodon, very much less so than in Scelido- theritim, but, as in the latter, the spines taper posteriorly to a point, filling the V-shaped notch in the palate. The posterior nares are narrow in front, broadening rapidly behind ; the side-walls, formed by the pterygoids and alisphenoids, have much the same shape as in Hapalops. The mandible, which is known only in this genus, not in the succeed- ing one, has already been described in the account of the family. No vertebrae have yet been identified, except a few in connection with one individual (No. 15,893), the reference of which, though very probable, is not entirely certain, because no tooth or part of the skull is associated with the specimen. The posterior thoracic vertebrae resemble those of the Santa Cruz Megalonychidce and have the centra perforated in the usual way by paired canals opening on the ventral surface ; the caudal vertebras also are not especially characteristic. On the other hand, the only lumbar associated with this specimen has a very peculiar type of transverse process, different from anything known in either of the preceding families ; the process is quite short, but the distal portion is very broad antero-pos- teriorly ; it is deeply notched on the anterior border and its base is perfo- rated by a large vertical foramen ; the shape of the process is thus deceptively like the inferior lamella of a cervical, except that it projects horizontally, not ventrally; the accessory articular processes are, as in , a small anterior pair, placed on the neural arch below the true EDENTATA OF THE SANTA CRUZ BEDS. 349 prezygapophyses, and a small posterior pair arising from the hinder edge of the transverse processes. The humerus (Plate LXIII, figs. 6, 6°, No. 15,374) was found isolated and is referred to the present genus because of its resemblance to that of Mylodon and its decided difference from the humeri of the two preceding families. Compared with the humerus of Hapalops, this specimen is strikingly short and heavy and all the processes for muscular and liga- mentous attachment are more prominent; the proximal end is broader, owing to the development of the tuberosities, of which the internal is rela- tively larger and more prominent than in Mylodon, and the bicipital groove is shallow; the shaft is stout; the pectoral ridge is distinct and the deltoid area is much broader than in Hapalops and near the distal end its borders project more prominently; the supinator ridge and external epicondyle are much better developed than in Hapalops and the former has a greater proximo-distal extension than in Mylodon, making the mus- culo-spiral groove very conspicuous ; the internal epicondyle is extremely large and is perforated by the usual large foramen. The trochlea is inter- mediate in character between that of Hapalops and that of Mylodon, dif- fering from the latter in the narrow hemispherical facet for the radius and in the better definition of the groove on the posterior side for the ulna, and from the former in the flatness of the ulnar facet, which is hardly reflected at all upon the dorsal side ; the anconeal fossa is small and shallow. The dimensions of this humerus are as follows : Length 160 Distal width over epicondyles 072 Proximal width 055 " " " trochlea 042 The radius (Plate LXIII, figs. 7, 8; No. 15,893) is conspicuously short and stout and may be described as intermediate in character between Hapalops and Scelidotherium. The head, which is much damaged, appears to have been discoidal in shape; the bicipital tubercle is very large and rugged and has a slightly more distal position than in Hapalops; the proximal part of the shaft is broader and shorter than in the last named genus, but has a similar shape, while the distal broadening, though more gradual, is much greater, and the external border is more thickened ; the carpal surface is larger in both dimensions and the styloid process is some- what more pronounced. The length of this radius is 123 mm., and its distal width is 30 mm. 350 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. The first metacarpal is characteristically like that of Mylodon, though it is relatively longer and more slender. Owen's description of this bone in the Pleistocene genus applies almost exactly to Nematherium ; it "pre- sents a very singular and anomalous figure, in consequence of a thick and short process which is sent off from the ulnar side of its base, which gives it the appearance of being bent at a right angle" ('42, 90-91). This process, though not so long as in Mylodon, is very conspicuous and gives to this metacarpal an entirely different appearance from that of the Santa Cruz genera of the Megalonychidcz and Planopsidcz. Other differences which this specimen displays from the first metacarpal of Mylodon are the concave instead of the plane facet for the trapezium, the longer and more slender shaft, and the well developed distal trochlea, with its prominent keel. The dimensions are as follows: Length, 26 mm.; proximal width, 1 8 mm.; distal width, 9 mm. A third individual (No. 15,965, text figure 38), which consists of the astragalus, navicular, part of the calcaneum, and the distal end of the fibula, FIG. 38. Nematherium sp. Left astragalus, dorsal and ventral views and left calcaneum, dorsal view, x {. No. 15,965- is referred, with some hesitation, to Nematherium, chiefly because of its marked difference from the two preceding families, and a certain likeness to Mylodon. The distal end of the fibula is a very massive external mal- leolus, much like that of Hapalops, but with a somewhat larger facet for the tibia. The astragalus has a narrow, elongate form, quite similar to that of the Megalonychidcz, but a marked and suggestive likeness to Mylodon is seen in the trochlea; the inner condyle has a very distinct tendency to assume the odontoid shape and is much less extended prox- imo-distally than the external condyle. In the astragalus of Prepotherium EDENTATA OF THE SANTA CRUZ BEDS. 351 also the inner condyle has begun to be odontoid in form, but in quite a different fashion and without any likeness to Mylodon. Another differ- ence from the astragalus of the Megalony chides, seen in that referred to Nematherium, is the division of the internal calcaneal facet into two dis- tinct surfaces, which are almost at right angles to each other, while the cuboid facet is smaller and the navicular facet is shallower. This astrag- alus measures 35 mm. in length and 27 mm. in greatest width. The navicular resembles that of Hapalops, except that the inner border is somewhat less produced proximally. In the fragment of the calcaneum the only noteworthy feature is the presence of a second internal astragalar facet, corresponding to the division of the inner calcaneal surface of the astragalus. Relationships. — The materials for the study of Nematherium are tan- talizingly incomplete and entirely insufficient for any final determination of its taxonomic position. However, so far as this material goes, it is all in favor of the conclusion that this genus is a forerunner and quite pos- sibly an actual ancestor of Mylodon, while its reference to the family of the MylodontidcB appears not to be open to question. The resemblances to Mylodon are especially marked in the scanty remnants of the limbs and feet, which are just what we should expect to find in an ancestor of that genus, while the anterior broadening of the palate and rostrum, though not at all striking, is another significant resemblance. At the same time, we find many points of similarity between Nematherium and Scelidothe- riwn, especially in the characters of the teeth and skull, so that much might be said in favor of regarding the Santa Cruz genus as nearly, if not quite, representing the common ancestor of the two Pleistocene genera. Even though the relationship between the earlier and the later genera should prove not to be so simple and direct as is here assumed, these Santa Cruz species would not be without importance, because they would then represent what might be called arrested stages in the development of the family, which, as Tournouet has shown ('03), was already in existence in pre-Patagonian times. While the resemblance of Nematherium to Mylodon and the propriety of referring the former to the Mylodontidce are sufficiently obvious, it is of interest, on the other hand, to observe the many likenesses to the con- temporary members of the Megalonychidcz and the Planopsidce. So many and so close are these likenesses that, if the Santa Cruz genera of the 352 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. Gravigrada were now living, we might well include them all in a single family. In the structure of the skull, the vertebral column, the limbs and feet, there is a remarkable uniformity of plan throughout all the genera, and this uniformity is clearly to be interpreted as indicating the common origin of the three families and the relatively small degree of divergence which they had attained in the Santa Cruz epoch, as compared with the differences which separated their Pleistocene representatives. NEMATHERIUM ANGULATUM Ameghino. (Plates LXIl, Fig. 3 ; LXIII, Figs. 3-50.) Nematherium angulatum Amegh. ; Enumeracion sistematica, etc., 1887, p. 22. Nematherium sinuatum Amegh. ; Ibid. Nematherium longirostris Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 324. Nematherium lavagnanum Mercerat; Rev. del Mus. de La Plata, T. II, 1891, p. 26. This, the typical and most abundant species, is of medium size and is characterized by a certain degree of constancy in the forms of the teeth, though there is much variability also. In the upper jaw - is subcylin- drical, i-A are distinctly triangular and bevelled by wear, with a smaller anterior and larger posterior worn surface ; - is horizontally worn and less distinctly triangular than - or *-. In the mandible T is triangular, -% and ? are quadrangular and lozenge-shaped and ¥ is more elongate antero-posteriorly ; T is bilobate, but no two specimens agree in the rela- tive size of the two lobes, which is often different on the two sides of the same mandible. The anterior divergence of the two rows of teeth is more decided than in some of the other species. Of the skull only one imperfect specimen is known and that displays little that is characteristic. The mandible has a long, obtusely pointed predental beak, the dorsal border of which is raised above the level of the teeth ; the ascending ramus is broad and the coronoid erect. In the following table the measurements are from the type of N. longi- rostris in the Ameghino collection. EDENTATA OF THE SANTA CRUZ BEDS. 353 MEASUREMENTS. Upper dentition, length 042 i, width 007 1, length (i. e., antero-posterior diam- $-, length 008 eter) 005 " width 007 " width (i. e., transverse diameter). . . .0055 &, length 007 S-, length 007 " width 005 " width 005 Palate, width at 1 016 •3-, length 008 In the succeeding measurements No. i is the type of N. lavagnanum in the La Plata Museum. No. i. No. 15,530. Lower dentition, length 040 .0385 r, length 008 .008 " width 005 .005 j, length 0085 .008 " width 006 .006 3- length 009 .009 " width 0065 .0065 ^, length 013 .0125 " width 007 .006 Width of jaw between -j .016 " " " " Tf .010 Mandible, depth at ? 0264 .026 height of coronoid -°59 length of predental beak .037 NEMATHERIUM AUCA (Ameghino). (Plate LXII, Figs, i, i", 6.) Lymodon auca Amegh.; Rev. Argent, de Hist. Nat; T. I, 1891, p. 324. Lymodon perfectus Amegh. ; fenum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 166. The type of Lymodon aiica is an imperfect mandible and that of L. per- fectus is the right half of the skull, with teeth ; the two specimens agree so well that they might almost pertain to the same individual. This species is one of the largest Santa Cruz representatives of the present family ; the teeth are horizontally abraded, with some slight indications of bevelling on one or more of them ; - is nearly cylindrical, though somewhat flat- tened on the inner side ; -~- are very obscurely triangular, almost trape- zoidal. In the mandible, T is triangular, with the apex behind ; ^ and ^ are also triangular, but much compressed antero-posteriorly, broad trans- 354 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. versely and set obliquely to the line of the jaw ; T has an unusually long posterior lobe. The skull, so far as it is preserved, differs little from that of other members of the family ; its upper contour is regularly arched from the occiput to the end of the muzzle, and the preorbital region is quite short ; the facet for the jugal on the maxillary is an unusually large and deep, triangular depression. The measurements in the subjoined table are from the types in the Ameghino collection. MEASUREMENTS. Upper dentition, length 056 -6-, width 007 1, length (i. e., antero-posterior diam- Skull, length 210 eter) oio Lower dentition, length 056 " width (/. e., transverse diameter) . . . .007 T, length 0065 1, length oio " width 006 " width 008 if, length 006 i, length 0105 " width 008 " width 0095 5, length 006 . A, length oio " width 0095 " width 0085 T, length 020 *-, length 0085 " width on NEMATHERIUM PROFUNDATUM (Ameghino). (Plate LXII, Figs. 2-2" ; Plate LXIII, Fig. 2.) Ammotherium profundatum Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 325. Ammotherium aculeatum Amegh. ; fenum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 168. The type of Ammotherium profundatiim is the nearly complete man- dible of a rather old individual, with all the teeth in place, while that of A. aculeatum is a finely preserved skull, with lower jaw, but lacking the ascending ramus. There are, it is true, many differences between the two specimens, but, in view of the great variability which characterizes this whole group, it seems hardly probable that they represent two distinct species. On the other hand, the palate with teeth which Ameghino subse- quently referred to A. profundatum ('94, 168) (Plate LXII, fig. 5) may well pertain to a different species. In size, this is one of the largest of the Santa Cruz Mylodontidcz, though somewhat smaller than the preceding species. In the type of A. aculeatum EDENTATA OF THE SANTA CRUZ BEDS. 355 - is of compressed elliptical section and of remarkably small size, while -~- are of unusually well-defined triangular form, and A is less distinctly so. The two series of upper teeth diverge anteriorly in only a moderate degree, while in the palate above mentioned the divergence is much more decided and - is large and 'triangular. In the mandibular dentition there is considerable difference between the types of A. profimdatum and A. acitleatwn, and even on the opposite sides of the same jaw. In the former 2 is more cylindrical and -3 more antero-posteriorly compressed, while in the latter 2 is more triangular and T has a remarkably broad posterior lobe ; in both T is of compressed elliptical section and has a large, deeply notched surface of abrasion on the hinder face. The skull, as displayed in the type of A. aculeatum, is very elongate and quite broad posteriorly, the cranium reaching its maximum width at the glenoid cavity, and thence narrowing to the interorbital region, while the face is very slender, though the rostrum broadens somewhat anteriorly. The occiput is low and the upper contour of the skull, which rises but little to the parietal eminence, has a nearly horizontal and slightly sin- uous course. The basioccipital and basisphenoid are very broad ; the con- dyles are quite small and are separated ventrally by a wide and deep notch. The preorbital region is somewhat longer than in any other spe- cies ; the palate is very narrow and quite strongly convex behind, widen- ing and flattening anteriorly, and is continued for a short distance behind the last tooth ; the median notch for the premaxillary spines is a deep and harrow V. The posterior nares follow the shape of the cranium, being very broad behind, contracting forward and becoming very narrow at the front border. The mandible is best shown in the type of the species, in which it differs in a number of respects from that of N. angulatum ; the coronoid is more recurved and inclined ; the condyle is placed upon a longer neck and is more raised above the level of the teeth, while the angular process appears to have been much longer. In the type of A. aculeatum, the predental beak has more nearly parallel sides and an elevated dorsal border. In the following table No. i is the type of Ammotherium profundatum, No. 2 the palate referred to the same species, and No. 3 the type of A. acttleatum, all in the Ameghino collection. 356 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. MEASUREMENTS. No. i. No. 2. No. j. Upper dentition, length .046 .045 J-, length (i. e., antero-posterior diameter) .007 .0062 " width (*. e., transverse diameter) .0065 .0038 i, length .009 .0075 " width .008 .0062 i, length, .007 .0075 " width .009 .0075 A, length .008 .007 " width .0075 .0075 i, length .007 .0075 " width .006 .0062 Lower dentition, length .044 .042 T, length 0075 .008 " width 006 .005 ?, length 007 .0065 " width 006 .006 7, length 007 .008 " width 0075 .007 j, length .014 .014 " width 009 .0085 Skull, length in median basal line, excluding premaxillae. .159 Skull, length condyle to anterior nares .184 Cranium, length condyle to rim of orbit . 1 375 Face, length orbit to anterior nares .0465 Occiput, height .046 " width .060 Zygomatic arch, length .089 Distance, occipital condyle to glenoid cavity .034 Palate, length in median line .061 " width at-1- .019 .017 " " &• .010 .009 Mandible, length from condyle .157 " " of predental beak .05 1 .044 + depth below ¥ 032 .0285 " height of coronoid .070 " condyle 060 NEMATHERIUM DECLIVUM (Ameghino). (Plate LXII, Figs. 4, 4°.) Ammotherium declivtim Amegh.; fenum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 168. EDENTATA OF THE SANTA CRUZ BEDS. 357 This doubtful species, which is known only from the type, is the smallest of the genus, though not much inferior to the smaller specimens of N. angulatum. MEASUREMENTS. Upper dentition, length 037 Lower dentition, length 036 1, length (*'.£., antero-posterior diameter) .0045 T, length 007 " width (i. e., transverse diameter) . . . .004 " width 004 ^, length 007 j, length 006 " width 005 5 " width 005 A, length 007 T> !ength 0075 " width 007 " width 005 5 A, length 007 -%, length 013 " width 005 5 " width 005 £, length 0065 Palate, width at 1 015 " width 004 " " " £ 009 ANALCITHERIUM Ameghino. Analcitheritim Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 325. Scelidotherium Lydekker, in part ; Anales del Museo de La Plata, T. Ill, 1894, p. 92. The separation of this genus from Nematherium may prove to be un- necessary, but, for the present at least, seems to be advisable, because of its greater likeness to Scelidotherium, which has led Lydekker to refer it to the latter. The most important distinction from Nematherium consists in the much less decided anterior divergence of the dental series and the parallelism of the sides of the rostrum, while the preorbital region is rela- tively short. Assuming the propriety of separating this form generically, it seems probable that it is more particularly related to Scelidotherium, as Nem- atherium is to Mylodon. ANALCITHERIUM ANTARCTICUM Ameghino. (Plate LXIII, Figs, i, IB.) Analcitherium antarcticum Amegh. ; Rev. Argent, de Hist. Nat.. T. I, 1891, p. 325. Scelidotheriiim antarcticum Lydekker ; Anales del Museo de La Plata T. Ill, 1894, p. 92. The typical and only known specimen is the skull, lacking the occiput, basis cranii, zygomatic arches, and mandible, of a very young animal, and 358 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. certain of its characteristics may be due to immaturity. The anterior upper teeth (-1- and *) are of compressed, subelliptical shape, flattened on the inner side ; * and A are triangular, with rounded angles, and - is ob- scurely so ; the two dental series are nearly parallel, with only a slight ante- rior divergence. The skull is very similar to that of Nematherium in form, being broad behind, contracting rapidly forward to the interorbital region, and with elongate and very slender face. The occiput is low and the upper contour of the skull is gently arched from before backward ; the preorbital portion of the face is distinctly shorter than in any species of Nematherium in which the skull is well known, and the predental part of the maxillary is also shortened ; the palate is of nearly uniform width and but slightly convex posteriorly, where it is not continued so far behind the last tooth as in the preceding genus. MEASUREMENTS. Upper dentition, length 039 Skull, length occiput to anterior nares . .150 1, length (i. e., antero-posterior di- Cranium, length to rim of orbit 114 ameter) 006 Face, length orbit to anterior nares . . . .036 " width (i. f., transverse diameter) . . . .0045 Occiput, height 031 -2, length • 007 Cranium, width at glenoid cavity 052 " width 005 Zygomatic arch, length 075 i, length 0065 Rostrum, width at infraorbital foramina .024 " width 0065 " " " anterior end 021 A, length 008 Palate, length in median line 047 " width 007 " width at J- 0135 «, length 006 " " " *• oio " width 004 EDENTATA INCERTyE SEDIS. In addition to the foregoing genera Ameghino has named a number of others, some of which he has referred to the Monotremata. These genera are very imperfectly known and, as I am not in a position to add anything to what has already been published, merely the names and references are here given. TREMATHERIUM Ameghino. Trematherium Amegh. ; fenum. Sistem. etc., 1887, p. 22. Trematherium Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 319. Schismotherium Mercerat, in part; Rev. del Museo de La Plata, T. II, 1891, p. 5. EDENTATA OF THE SANTA CRUZ BEDS. 359 Trematherium Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 169. Trematherium Amegh. ; Sec. Censo de la Repub. Argent. T. I, 1898, p. 209. TREMATHERIUM INTERMIXTUM Ameghino. Trematherium intermixtum Amegh.; Enum. Sistem. etc., 1887, p. 22. Schismotherium intermixtum Mercerat ; Rev. del Museo de La Plata, T. II, 1891, p. 8. Planops longiro stratus Mercerat, in part, Ibid., p. 8. Trematherium intermixtum Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 159. Trematherium intermixtum Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 209. TREMATHERIUM NANUM Ameghino. Trematherium nanum Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, P- 3i9- Trematherium nanus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 170. Trematherium nanum Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 209. ADIASTALTUS Ameghino. Adiastaltus Amegh. ; Revue Scientifique, T. LI, 1893. Adiastaltus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 184. Peltephilus Lydekker, in part. ; Anales del Museo de La Plata, T. Ill, 1894, p. 67. Adiastaltus Amegh.; Sec. Censo de la Repub. Argent., T. I, 1898, p. 225. ADIASTALTUS HABILIS Ameghino. Adiastaltus habilis Amegh. ; Revue Scientifique, T. LI, 1893. Peltephilus strepens Lydekker, in part; Anales del Museo de La Plata, T. Ill, 1894, p. 68. Adiastalttis habilis Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 184. Adiastaltus habilis Amegh. ; Sec. Censo de la Repub. Argent. ; T. I, 1898, p. 225. 360 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. ADIASTALTUS PROCERUS Ameghino. Adiastaltus procerus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 1 86. Adiastaltus procerus Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 225. PLAGIOCCELUS Ameghino. Plagioccelus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 1 86. PLAGIOCCELUS OBLIQUUS Ameghino. Plagioccelus obliquus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 187. ANATHITUS Ameghino. Anathitus Amegh. ; Revue Scientifique, T. LI, 1893. Anathitus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 187. Anathitus Amegh.; Sec. Censo de la Repub. Argent., T. I, 1898, p. 225. ANATHITUS REVELATOR Ameghino. Anathitus revelator Amegh. ; Revue Scientifique, T. LI, 1893. Anathitus revelator Amegh. ; Enum. Synopt. des Mamm. Foss. d. Pata- gonie, 1894, p. 187. Anathitus revelator Amegh. ; Sec. Censo de la Repub. Argent., 1898, p. 225. ENTELOPS Ameghino. Entelops Amegh. ; Enumeracion sistematica, etc., 1887, p. 23. Entelops Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Arg., 1889, p. 654. Entelops Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 109. Entelops Amegh. ; Sec. Censo de la Repub. Argent., T. I, 1898, p. 209. ENTELOPS DISPAR Ameghino. References as for the genus. EDENTATA OF THE SANTA CRUZ BEDS. 361 RELATIONSHIPS OF THE EDENTATA. It must be admitted that the Santa Cruz fossils throw but little light upon the very obscure and difficult problems concerning the origin of the Edentata and their relations to other mammalian groups. Such light can be obtained only from a fauna of much more considerable geological antiquity, though, if the exceedingly curious animals, which Ameghino has described as Adiastalttis and Anathitus and referred to the Monotre- mata, were better known, they might afford a valuable clue to the solution of the mystery. So far as it goes, the evidence of the Santa Cruz fauna is not in favor of Wortman's most interesting hypothesis ('96, '97) that the Edentata were derived from the Ganodonta. This hypothesis rests chiefly upon a series of resemblances between the latter group and the Pleistocene genus Mega/onyx, and more especially upon the identification of the first tooth in each jaw of the Gravigrada as a canine. Even in regard to the upper tooth this identification is exceedingly doubtful, and there is much more reason to consider the tooth a premolar. In the case of the lower tooth, however, the determination is clear, for this tooth, almost without exception, bites behind the upper caniniform and therefore cannot itself be a true canine. More important is the fact that the Santa Cruz Gravigrada are less like the Ganodonta than are the Pleistocene genera, which of course would not be the case if the Ganodonta were the true ancestral group ; we should then find that the farther back the eden- tate line were traced, the more closely it would approximate the ganodonts. Wortman too is quite mistaken in supposing that the earliest appearance of the edentates in South America "does not antedate the Santa Cruz epoch" ('97, 104). On the contrary, they occur in the oldest known Tertiary, and possibly even pre-Tertiary, deposits of Patagonia, and there is every appearance of their having been indigenous in that region. It cannot be pretended that the evidence of the Santa Cruz fauna definitely disproves Wortman's hypothesis, but it does render it distinctly less prob- able. On the other hand, Osborn's recent discovery of a true armadillo in the Bridger Eocene of North America ('04), removes the formidable geographical difficulty which had formerly attended that hypothesis. Although the Santa Cruz fauna thus gives us little help in determining the relationships of the Edentata to other mammalian orders, it affords abundant testimony to the unity of origin of the American edentates. 362 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. The so-called edentates of the Old World have very little in common with the American orders and probably are not related to them. At all events, the Santa Cruz fossils do not even tend to bridge the gap between the two series. As was pointed out in a previous section (this volume, p. 4), there is strong reason to believe that all of the edentate orders had come into existence as such before Santa Cruz times, although no representatives of the ant-eaters or of the true sloths (Tardigrada) have yet been found in the Santa Cruz or older formations. It is doubtless true of those two orders, as it is of the three others, Dasypoda, Glyptodontia and Gravi- grada, which are well represented in the Miocene fauna, that at that time the various subdivisions of the edentates had not yet become so widely separated by divergent evolution as they afterwards were. In other words, as we trace these groups backward in time, we find them converging more and more closely to a common term, and this is a highly significant fact, as indicating their monophyletic origin from a single ancestral group. It further appears probable that the five orders, or suborders, of the Edentata did not arise simultaneously from the hypothetical ancestral group, but that the first division was into two principal branches. One of these branches subsequently gave off the armadillos and glyptodonts, while the other divided into the ground sloths, ant-eaters and true sloths. This conclusion is indicated by a comparison of the Santa Cruz arma- dillos and glyptodonts, on the one hand, with those of the Pampean, on the other, which shows not only that these two orders were much nearer together in the former epoch than in the latter, but also that they were more like each other than either is like any other order of edentates. This resemblance is by no means confined to the presence of a dermal armor in both groups, but extends to nearly all parts of the skeleton and even, in some small degree, to the dentition, and justifies the inclu- sion of both orders in the higher group Loricata. It would be very interesting to learn whether the earliest edentates possessed dermal ossifications. That such was the case, is rendered to a certain extent probable by the presence of these ossifications in the Pleis- tocene Mylodontidce. On the other hand, no trace of armor has been found in association with any of the Santa Cruz Gravigrada, though the extremely scanty and imperfect remains of the Mylodontida in the beds of that epoch deprives this fact of importance, so far as that particular EDENTATA OF THE SANTA CRUZ BEDS. 363 family is concerned. For the Megalonychidce and Planopsidce, the number of well preserved skeletons and parts of skeletons already collected is so large as to make the negative evidence very strong. If the ancestors of the Gravigrada had dermal ossifications, these ossifications had been lost in all except one family before the Santa Cruz epoch. It is of course possible that the dermal armor was independently acquired by the Mylo- dontidce and at a comparatively late period. Materials are lacking for a definite decision between these two alternatives, though perhaps the least unlikely assumption is as follows : That the single ancestral group of American edentates possessed dermal ossifications which were not exposed on the surface or covered merely with epidermal scales, but concealed within the skin, which was covered with hair; that in the Loricata they gradually assumed the forms so familiar in the glyptodonts and armadillos, while in the other orders they were lost, except in a single family of the Gravigrada. In the absence of the ancestral forms of the true sloths and the ant- eaters, it is difficult to reach any definite conclusions concerning the second great branch of the American edentates, though it is possible to draw a number of probable inferences from a study of the Santa Cruz Gravigrada. As has been shown in detail in the preceding pages, the skeleton of these animals is very much less specialized than it became in their Pleistocene successors and, what is of particular significance, the Santa Cruz ground sloths are very much closer to the ant-eaters in structure than are those of the Pampean beds. Aside from the skull, all parts of the skeleton, the vertebral column, the limb-girdles, limbs and feet display this resem- blance in a very marked manner, and it seems hardly open to question that the Vermilingua and the Gravigrada had a common ancestry, a conclusion which was long ago reached by Flower ('76) though upon somewhat dif- ferent grounds. The skull is, of course, very different in the two groups, but the differences are not of such a kind as to preclude the common origin of both. Even more closely connected are the Gravigrada and the Tardigrada ; the resemblance is most clear in the dentition and skull, but there are also many points of likeness throughout the skeleton. That the skeleton of the Tardigrada should be extremely peculiar, is not surprising in view of their very unusual habits ; the weight of the body is stispended from the limbs, not carried upon them in the ordinary fashion, and thus the me- 364 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. chanical character of the stresses is altered and what is normally compres- sion becomes tension. The entire bony structure is modified in accord- ance with this most exceptional arrangement and yet, in spite of this great modification, there are many notable resemblances between the modern Tardigrada and the Santa Cruz Gravigrada, so many as to render it altogether probable that both orders were derived from a single ancestral type. The backward convergence in time of the edentate orders is even more conspicuously shown by the families within those orders. All the Santa Cruz glyptodonts are very closely similar and the only reason for group- ing them into distinct families is because they seem to show, in an incip- ient and inconspicuous way, the first stages of those differences which became so very much more distinct in the subsequent epochs. Similarly, the three families of the Gravigrada were, in Santa Cruz times, very closely alike to one another, differing only in details of a very minor kind. Had the ground-sloths become extinct at the end of the epoch, instead of persisting till a much later time, no division into families would seem to be necessary, for the differences are significant only as foreshadowing the far more important differences of subsequent epochs. In the case of the armadillos the evidence is less satisfactory, for the Santa Cruz beds have as yet yielded the probable ancestor of only a single modern genus, while those of other recent families and genera must, it seems likely, be sought in a different region. Taken as a whole, how- ever, the testimony of the Santa Cruz fauna to the unity and close rela- tionship of all the American edentates, is very cogent. PART II. INSECTIVORA. At the present time continental South America contains no representa- tive of the Insectivora. Unusual interest therefore attaches to Ameghino's discovery of the genus Necrolestes in the Santa Cruz beds, which was an- nounced in 1891. In his first account Ameghino suggested that this curious fossil had analogies with the Cape golden moles of Africa (Chry- sochloridce], but in a second paper (1894) this suggestion is not repeated and the genus is referred to a new family, the Necrolestidce. The material collected by Messrs. Hatcher and Peterson adds largely ^to our knowledge of this genus and the result of a comparison with the skeletons of Chry- sochloris and the Marsupial Notoryctes is to confirm Ameghino's original suggestion of a relationship between the African genus and Necrolestes. The new family name is, however, provisionally retained, because it would be premature, and perhaps entirely misleading, to refer the fossils to the existing family. NECROLESTIDsE. NECROLESTES Ameghino. (Plate LXIV, Figs. 1-5.) Necrolestes Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 303. The dental formula is If, Cf, Pf, Mf . In the upper jaw the incisors diminish in size, though not regularly, from the median to the lateral one ; i- is nearly and sometimes quite as large as \-, while i4 is smaller and i- considerably smaller than the anterior pair ; i1 is slightly recurved and antero-posteriorly compressed, giving it some resemblance to a very short rodent tooth, while the others are laterally compressed. Viewed from the outer side, the crowns of all the incisors have a rectangular, almost square shape and those of i1 and - are faintly grooved ; each incisor is carried on a single fang. In Chrysochloris the incisors are three in number ; \- is much enlarged and i^ and especially ia much reduced ; the crowns are acutely pointed and minute accessory basal cusps are present in some of the 365 366 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. species. Notoryctes has greatly reduced incisors, which in their quadrate form bear a certain resemblance to those of Necrolestes. The canine is much the largest and most prominent tooth of the upper jaw ; at the base the crown is broad and thick, but it tapers rapidly to an acute point ; in shape, it is obscurely trihedral, with flattened anterior and grooved inner faces, and sharp posterior edge ; the whole tooth is some- what recurved. The great size of the canine is in marked contrast to both Chrysochloris and Notoryctes, in which this tooth is much reduced and smaller than any of the incisors. The premolars are three in number, and only the anterior one, probably p-, differs appreciably from the molars in structure ; it is inserted by two fangs and has an acutely pointed, compressed-conical crown, with tren- chant anterior and posterior edges and small anterior basal cusp. The succeeding five teeth are alike except in size, with trigonodont crowns, which closely resemble those of Chrysochloris, but are less completely hypsodont and lack the pointed, cusp-like pillar which, in the recent genus, arises from the inner apex of the triangle. As in the latter, pA is the largest of the grinding teeth, the molars diminishing in size posteriorly ; ma is very small, though not so minute as in Chrysochloris. In Notoryctes the premolars are very small and simple. In the lower jaw the four single-rooted incisors have laterally com- pressed quadrate crowns and decrease in size from iT to iT. In Chryso- chloris iT is very small and % the largest of the series, and the crowns of all three are more curved and pointed, less compressed than in the fossil, while in Notoryctes these teeth are almost rudimentary. The canine is very large and has a high, broad, trenchant, recurved and acutely pointed crown, which, when the mouth is closed, is received into a deep notch in the side of the upper jaw. Ameghino states that this tooth is implanted by two roots, which in the individual figured by him ('94", 107, fig. 43) are very greatly swollen ; in none of the specimens of the Princeton col- lection are the fangs so much swollen, though one of them is not very different in this respect. In Chrysochloris the lower canine is smaller than i^ and in Notoryctes it is greatly reduced. The foremost premolar (p^) resembles p- in form, but has both anterior and posterior basal cusps. The next five teeth (p^— m¥) differ from one another only in size ; they are trigonodont and hypsodont, much like those of the African genus, but not so high and somewhat longer antero-pos- INSECTIVORA OF THE SANTA CRUZ BEDS. 367 teriorly, while nr% is less reduced. In all the grinding teeth, upper and lower, the cusps are early worn away, leaving more or less cordiform masticating surfaces (PI. LXIV, Fig. 3*). As a whole, the dentition is both like and unlike that of Chrysochloris ; the likeness is in the grinding teeth, the only noteworthy differences here being the less completely hypsodont character, the absence of the internal pillar in the upper teeth and the less extreme reduction of 1113 in both jaws. The unlikeness is in the incisors, canines and foremost premolar, which in Chrysochloris are all small and of similar form. In Notoryctes the molars resemble those of the other two genera, but all the antemolars are minute and have evidently been much reduced. The skull of Necrolestes is very similar indeed to that of Chrysochloris and although it is, in most respects, less modified and peculiar and in a few points more so, it is of an identical structural type. The skull is longer and more tapering anteriorly than in the modern genus, and the muzzle is prolonged in front of the incisors into a long, tapering, and up- turned snout, which gives a very peculiar appearance to the whole head, almost equally different from the short, broad, and abruptly truncated muzzle of Notoryctes and the longer, narrower muzzle of Chrysochloris ; the premaxillaries do not display the curious expansions seen in the lat- ter, though this difference is apparent rather than real, for the processes are concealed by the prolongation of the nasals, while in Chrysochloris the shortened nasals leave them exposed. As in the African genus, the -occiput is a broad, hemispherical swelling, somewhat less inflated, how- ever, and without so distinct a depression in the median vertical line.. A very short, but broad and distinct paroccipital process is present and en- closes a deep fossa immediately behind the glenoid cavity. The occipital condyles are notably large, especially in the transverse direction and the foramen magnum presents less ventrally than in Chrysochloris. One very marked difference from the modern genus consists in the very much less inflated and swollen character of the squamosal. In Chryso- chloris this bone, seen from the front, looks like a sphere attached to the side of the cranium, most of it internal to the zygomatic arch, but in the fossil there is no such appearance. The zygomatic arch is long and quite distinctly heavier than in Chrysochloris, but its root is not so expanded into a vertical crest as in the latter, in which these processes have a pecu- liar appearance of enfolding the skull and make the temporal fossae very 368 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. narrow and deep. In Necrolestes the roots of the zygomata are normal in character, and the arches curve upward more decidedly than in the ex- isting genus, in which they are very slender and almost straight. The glenoid cavity resembles that of the latter, but is somewhat larger and more deeply concave. The tympanic bulla is ossified and moderately inflated, though all the specimens are so damaged in this region of the skull as to render this determination slightly uncertain. The sagittal crest is very inconspicuous but it is longer and more dis- tinct than in Chrysochloris ; the occipital crest, on the other hand is a mere raised line and is much less elevated than in the latter. The cranium has not the straight, tapering tubular form characteristic of Chrysochloris, but is broader and has a faintly marked postorbital constriction, which is more distinct than in those species of Chrysochloris which possess it at all (C ruti- lans, C. aured]. A very slight angulation of the frontal represents the postorbital process, but it is hardly worthy of the name, and there is no corresponding process on the jugal. The nasals are long and tapering and at their anterior ends they are upturned in a curious fashion, so as to make their dorsal surfaces strongly concave. Thinking at first that this appearance might, at least in part, be due to distortion from pressure, I have examined with great care the specimen which displays this character and have reached the conclusion that the character is a natural one, though in a second individual it is not apparent and even the prolongation of the muzzle is lacking. This latter skull, however, has evidently been flattened by pressure normal to its upper surface and the snout appears to have been broken off just in front of the premaxillary alveoli, and although it is possible that a specific or even a generic difference may here be indicated, yet the agreement of the two specimens is otherwise so close and exact that such a difference does not seem likely. The premaxillaries are elongate antero-posteriorly and are completely fused in the median line. From the dorsal border of the horizontal ramus arises a slender, pointed, median spike, which extends obliquely upward and forward more than half way to the nasals and incom- pletely divides the anterior nares into two distinct openings, which present forward and very slightly downward. The maxillary is long and low and has a conspicuous preorbital prom- inence, formed by the alveolus of the large canine ; in front of this swelling, and made all the more obvious by the juxtaposition, is a deep constriction, INSECTIVORA OF THE SANTA CRUZ BEDS. 369 or notch, which receives the lower canine when the jaws are closed. The bony palate differs in several important respects from that of Chryso- chloris, though having a similar general character and shape, since it does not take part in the snout-like prolongation of the muzzle, which is all in front of the incisors and is formed chiefly by the nasals. The incisive foramina are conspicuous and are long, narrow slits, running nearly the whole length of the palatine processes of the premaxillaries and separated by a slender spine. In Chrysochloris these foramina are either obsolete or exceedingly minute. The maxillary portion of the palate is broad and is traversed by obscurely marked, curved ridges, with the convexity turned forward, these ridges resemble and doubtless correspond to those of the soft palate. The posterior ^nares have the same relative position as in the African genus, but are rather higher and broader and they are divided into two openings by an extension of the vomer throughout their length, which descends to the level of the bony palate and is united with the palatines in the median line of the front margin of the narial opening, making the vomer appear like a process of the palatines. This extension of the vomer is not found in Chrysochloris. The pterygoid fossae are not completely suppressed, as in the latter genus, but are represented only by shallow and inconspicuous grooves. The mandible is exceedingly like that of Chrysochloris, so much so as immediately to suggest a relationship between the two genera, but it dif- fers in a few minor details. The horizontal ramus is relatively longer and -has a more sinuous ventral border, while the rami of the two sides are somewhat less widely separated, converge more gradually forward and meet in a rather longer symphysis. The coronoid process is higher, broader, and more inclined backward, so that the sigmoid notch is not as widely open. The condyle is set upon a similarly elongated neck and is a transverse semicylinder, but the masseteric fossa, which is barely indi- cated in the modern genus, is quite deep and has a raised anterior border, though the fossa is small and placed high upon the ascending ramus. Doubtless the better development of the masseteric fossa in Necrolestes is to be correlated with the stouter zygomatic arch. The angle is decid- edly smaller and more hook-shaped and has no tendency whatever to inflection. The cranial foramina are difficult to make out in such a small skull. Such as are visible, however, are suggestively like those of Chrysochloris. 370 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. The condylar and carotid foramina are not displayed in any of the speci- mens. The foramen ovale is very large, more conspicuous than in the modern genus and is more widely separated from the "large opening which includes the sphenoidal fissure, foramen rotundum, and optic fora- men," for Dobson's description ('83) seems to apply to Necrolestes also. This opening is, however, considerably farther forward than in Chryso- chloris. The infraorbital foramen is larger and covered by a much heavier bony process than in the latter and the lachrymal foramen is also larger, but occupies a similar position. That the skull of Necrolestes is of the same type as that of Chrysochloris will be sufficiently obvious from the foregoing description, and although there are many differences between them, these differences are not greater than may often be found within the limits of a single family. In most re- spects, as would be anticipated, Necrolestes has the more primitive skull, as is especially to be seen in the uninflated squamosals, in the presence of a slight interorbital constriction, and in the undiminished strength of the zygomatic arches and the normal shape of their roots and the reten- tion of the masseteric fossa of the mandible. On the other hand, the re- markable, prolonged and upturned snout would seem to be a specialization in the fossil, though the lateral processes of the premaxillaries and the small median anterior spines arising from the horizontal rami in Chryso- chloris suggest that in the ancestor of that genus the muzzle may have once been much longer than in its existing representatives. In Notoryctes the skull is of a different structural type ; the occiput is vertical and flat- tened ; the face is very broad at the orbits, contracting abruptly into the short, blunt muzzle. The auditory bulla is extensively open and is partly made up of the alisphenoid, while the angle of the mandible is very dis- tinctly inflected. In brief, the skull of Notoryctes is in all essentials mar- supial, while those of Chrysochloris and Necrolestes are as distinctively insectivorous. The Vertebral Column. — None of the specimens is sufficiently well pre- served to make the vertebral formula apparent, although vertebrae from all the regions of the column are represented, most of them belonging to a single individual. The cervical vertebrae are very much like those of Chrysochloris; they have short, broad, depressed centra, without hypa- pophyses, and very slender neural arches, though some, at least, possess fairly well developed neural spines, while in the modern genus only the INSECTIVORA OF THE SANTA CRUZ BEDS. 371 axis is so provided. In neither Chrysochloris nor Necrolestes are the cervicals at all like the curiously reduced and ankylosed neck vertebrae of Notoryctes. The thoracic vertebrae also are like those of Chrysochloris, with small, subcylindrical centra, broad, depressed neural arches, and short neural spines, which, as in the African genus, all incline backward, there being no anticlinal vertebra. The spines and metapophyses are, at least in the posterior half of the region, somewhat better developed than in Chryso- chloris, as is also true of Notoryctes, though in the latter the spines are much more slender than in either of the insectivorous genera. The lumbar vertebrae number at least four and perhaps five. The centra are broad and depressed, and the neural spines are quite elongated and are directed obliquely backward, as in the African form. The spines are somewhat longer than in the latter and have less of a rectangular shape, their free ends being more curved and pointed and less abruptly truncated. The metapophyses also are more prominent, and the transverse processes, though nearly as much reduced in size, are further removed from them, arising from the centra and not from the arches. In Notoryctes the lum- bars are quite different from those of either of the other genera ; the first one is the anticlinal, with an erect spine, while the spines of the others incline forward. The spines also are much smaller and more slender than in the two insectivores ; the transverse processes, on the other hand, are much better developed, as are also the metapophyses, and the zyga- pophyses are of the interlocking cylindrical type. A remnant of the latter structure is observable in Necrolestes. The sacrum is very like that of Chrysochloris. Dobson gives the num- ber of sacral vertebrae in the latter as five, but of these only three are true sacrals and are in contact with the ilium. In Necrolestes the arrangement is the same except that the two succeeding vertebrae, which in the recent genus are fused with the sacrum, are free and separate. The centra of the sacral vertebrae are broader and heavier than in the African type and the neural spines are even more reduced, not uniting into a continuous ridge. The iliac surface is large. Notoryctes has a very peculiar sacrum, quite different from that of the other two genera ; it is very long and broad and on each side the transverse processes unite into a bony plate which is con- nected in front with the ilium and behind with the ischium, while ventral transverse processes (pleurapophyses ?) from the last two vertebrae are 372 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. likewise ankylosed with the ischium. The .sacrum thus appears to be covered with a small carapace. One very marked difference between Necrolestes and Chrysochloris is in the character of the tail, which in the latter is very short and rudimentary, but in the former was evidently quite long, stout and well developed. The anterior caudal vertebrae, at least, have complete spines, transverse processes, metapophyses and zygapophyses, which in the African genus are either obsolescent or wanting. On the other hand, the processes are not so long and prominent as they are in Notoryctes, nor have any ver- tebrae at all resembling the curious, massive distal caudals of the marsupial been found in connection with the Patagonian fossils. As a whole, the vertebral column is exceedingly like that of Chryso- chloris, but slightly less modified. The various processes and spines are not so much reduced and the tail is considerably longer and better developed. The fore-limb is curiously alike in all three of the genera here discussed, though it would seem that Necrolestes had been less completely adapted to a burrowing mode of life than either of the modern genera. Of the scapula not enough is preserved to display the form, but what remains resembles the corresponding part of Notoryctes rather than that of Chrysochloris. The postscapular fossa differs from that of the latter in being convex instead of coneave, as is also the case in the marsupial, and the neck is much narrower, and, as in the latter, the ridge which runs parallel with the spine near to the glenoid border is very prominently developed, and curving toward the spine almost forms a tube. This ridge is likewise indicated in Chrysochloris, but is very inconspicuous. The spine is high and recurved and evidently terminated in a long acromion, but whether the latter attained such exaggerated proportions as in the two existing genera, there are no means of determining. The glenoid cavity is a broad oval and quite deeply concave, and the coracoid is obsolete, as it also is in Chrysochloris, while in Notoryctes it is quite well developed. The humerus (Plate LXIV, figs. 4-4") is extraordinarily like that of Chrysochloris, with only a few minor differences. The head is large, strongly convex and of ovoid shape, with the long axis directed parallel to that of the shaft ; it is a little smaller but projects rather more behind the plane of the shaft than in the African genus. The tuberosities are also well developed, but the internal one is not so large as in Chrysochloris INSECTIVORA OF THE SANTA CRUZ BEDS. 373 and the bicipital groove is not so deep, while the shaft is more slender ; the crest for the attachment of the pectoralis major muscle is even more prominent and more acutely pointed, and is situated rather more proxi- mally upon the shaft. The supinator ridge is enormously developed in pro- portion to the size of the bone. The internal epicondyle has almost as extreme a development as in Chrysochloris, though the process is some- what shorter and extends rather less internally and more distally; the foramen is very small. The distal trochlea is broad but very low; the facet for the capitellum of the radius is much broader, but less prominent, and less spheroidal in shape than in the African type. The anconeal fossa is a mere transverse, shallow groove. The humerus of Notoryctes closely resembles those of the two insectivorous genera, though differing in some respects from both of them. The deltoid ridge, which is not apparent in the latter, is very prominent and ends in a process for the pectoralis major. The supinator ridge is exceedingly large and the internal epicondyle is very much as in the two Insectivora, but it lacks the foramen, and the shaft is so twisted that the epicondyle has received a more backward direc- tion. The trochlea resembles that of Necrolestes in the shape of the facet for the capitellum of the radius. The forearm bones (Plate LXIV, Fig. 5) of Necrolestes are strikingly like those of Chrysochloris with differences of only minor importance. The radius has a less discoidal and more broadly oval head, which has a quite deeply concave facet for the median convexity of the humeral trochlea ; the shaft is stouter than in the African type and has a more distinctly marked lateral curvature ; proximally its position is on the external side of the elbow-joint, but it crosses the ulna, running most of its course in front of the latter, while distally it is internal ; the distal end is relatively broad and its anterior face is grooved by shallow sulci for the extensor tendons. The ulna has a remarkably elongate olecranon, which closely resembles that of Chrysochloris, but is rather shorter and broader ; the process is sickle-shaped and curves toward the internal side of the arm, or mesially, with the external border convex and the inner one concave ; this curvature is more pronounced than in Chrysochloris; the anterior face of the process is almost plane, but the posterior face is made convex by a prominent median ridge. The sigmoid notch is a short, but deep trans- verse - groove and the coronoid process forms a prominent ridge. The shaft of the ulna is stouter than in the golden moles and the distal end is 374 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. a bluntly rounded point, with a prominent ridge external and anterior to it. The forearm bones of Notoryctes have a curious resemblance to those of the two insectivorous genera ; the radius is shorter, but its transversely oval head is more like that of Necrolestes; the olecranon of the ulna is much more slender and more decidedly curved than in the fossil, curving more posteriorly and less internally. As is well known, Chrysochloris possesses a third fore-arm bone, which is as long as the radius and which runs from the palmar face of the carpus to the elbow joint, where it has a ligamentous connection with the entepi- condyle of the humerus. Flower regards this as apparently " an ossifica- tion in one of the flexor tendons " ('85, p. 275). The same structure appears to have been repeated in Necrolestes, though only the distal portion of it is ossified. Of the carpus are preserved in one individual the scaphoid, lunar, trape- zoid and magnum, and in connection with the latter the third metacarpal. A second specimen contains the pyramidal and unciform. Though much less reduced and specialized, the resemblance of these carpal bones to those of Chrysochloris is unmistakable. The scaphoid is a very large bone pro- portionately ; it is much like that of the African genus, but relatively larger ; the radial facet takes up but little of the proximal end of the bone, where it forms a small convex prominence. The palmar side of the scaphoid bears an articular surface, though it is not apparent what purpose this facet may have served. The distal end carries three facets, for the trapezium, trapezoid and magnum respectively, all of which are concave in shape, and that for the trapezium is exceedingly small ; the facet for the magnum is small but distinct. The lunar is much smaller than the scaphoid, though, like the latter, relatively larger than in Chrysochloris. It has a broad, convex proximal facet for the radius, which descends well upon the anterior face of the bone. The distal articulation appears to be entirely with the magnum, and if there was any contact with the unciform, it must have been a very limited one. The pyramidal is likewise proportionately larger than in Chrysochloris and covers the whole distal end of the ulna ; it is short proximo-distally and rather broad. The trapezium is not preserved in any of the specimens, but its presence may be inferred from the facet on the scaphoid. The trapezoid is exceed- INSECTIVORA OF THE SANTA CRUZ BEDS. 375 ingly small, but may, nevertheless, have supported a well developed digit. The magnum is considerably larger than the trapezoid and in shape resembles that of Chrysochloris more than do the other carpals. Proxi- mally it is covered almost entirely by the lunar, but also sends out a short process to reach the scaphoid. Distally, it supports only the third meta- carpal and appears to have no connection with the second. The unciform is relatively very small, especially in the proximo-distal diameter, which gives it a flattened, almost scale-like appearance ; evidently, it is beginning to undergo a marked reduction. In Chrysochloris the carpus has experienced an extraordinary degree of modification and reduction ; the central is suppressed, as are also the trapezium and trapezoid, the second metacarpal articulating directly with the scaphoid. There are thus only two bones in the distal row of the car- pus, the magnum and the unciform, and of these the unciform is much reduced, as is also the pyramidal. The number of metacarpals present in Necrolestes was probably five, though only two, the third and fourth, are preserved in connection with the carpus. From the size of the trapezium, trapezoid, and unciform it may be inferred that the metacarpals did not differ greatly in size and that there was no such enlargement of me. Ill at the expense of the others as has taken place in Chrysochloris. The third metacarpal is short and stout, but not nearly so broad as in the African genus, and it entirely lacks the relatively great extension toward the external side which in the latter reaches to the ulna. The proximal end bears a saddle-shaped sur- face for the magnum and the distal end has a nearly plane, very slightly saddle-shaped facet, which is very oblique to the axis of the shaft, sloping downward and forward. This distal end is very different from that seen in Chrysochloris, which is modelled for articulation with the great ungual and looks as if the first phalanx (if not the second also) were ankylosed with it. The fourth metacarpal is but little smaller than III, which it resembles in shape; it articulates with the unciform and is not, as in Chrysochloris, received into a depression beneath the great ulnar projection of me. III. In Chrysochloris the metacarpus is exceedingly peculiar ; me. I is very small and is attached to II ; the latter is larger, though very slender, and is carried by the scaphoid ; me. Ill is relatively very large, while me. IV is very much smaller and is carried by me. Ill, while me. V is wanting. 376 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. The phalanges of Necrolestes are present in normal numbers. Those of the proximal row are shortened to an extreme degree and are hardly more than irregular discs of considerable breadth. Those of the second row are minute in size, but are well formed, having a distinctly defined proximal trochlea, and a pulley-like distal trochlea. The un- gual phalanges are all of moderate size, that of the third digit not being enlarged into the great trowel-like bone seen in Chry- sochloris, nor are those of the other digits reduced in anything like the same degree. In shape, these unguals are all of simi- lar type ; they are slender, pointed, slightly compressed and de- curved, and cleft at the distal end. At the base of the phalanx ges of digit ... ... . ill left is a raised rim, like an incipient bony hood, which overhangs manus, of and conceals the proximal articular surface. This surface has Necrolestes two distinct pits divided by a median ridge, and is so deep and \afc*~ oblique that the other two phalanges of each digit are concealed a p'halan- fr°m sight, when the manus is viewed from the dorsal side, ges from There is a large flat subungual process. the outer Incomplete as are these fossils, they suffice to make it clear ade. b. Un- that ^g manus of Necrolestes is very much less modified than that of Chrysochloris, having the normal number of carpals and phalanges, while all of the digits appear to be of approximately equal size. At the same time the highly differentiated manus of 'Chryso- chloris might very well have been derived from such a type as that of the Patagonian fossil, and the modifications seen in the latter all tend in the direction of the African genus, as may be observed in the peculiar shape of the magnum, the reduction of the unciform, the suppression of the centrale, and in the shape of the phalanges. The manus of Notoryctes bears a superficial resemblance to that of Chrysochloris, a resemblance which is given by the great' enlargement of the third ungual and still greater size of the fourth, but all the bones of the hand are of a different type and the unguals are not cleft at the tip. The pelvis differs from that of both the modern genera, though it is most like that of Chrysochloris. The ilium is long, slender, rounded, and very slightly expanded at the anterior end. It is more elongate and more expanded anteriorly than in the African form, but otherwise resem- bles the latter and is quite different from the ilium of Notoryctes, in which the anterior expansion is far greater and is coossified with the transverse INSECTIVORA OF THE SANTA CRUZ BEDS. 377 FIG. 36. processes of the sacrum. The ischium is short and without tuberosities ; it is deeper vertically than in Chrysochloris, though far less so than in Notoryctes, in which the bone is of a totally different shape and is ankylosed with the transverse processes of the sacrum. The pubis is long, apparently meeting its fellow of the opposite side in a symphysis (as is not the case in Chrysochloris] and the obturator foramen is large. One of the greatest peculiarities of Chrysochloris is the reduction of this foramen to two minute perforations, and associated with this is the entire absence of any pubic symphysis, the two pubes being more widely separated than are the two ilia. In Notoryctes also, despite the very large size of the ischia, the obturator foramina are very much reduced. In short, both the African and the Australian genus have curiously modified pelves, though modified in entirely different fashion in each case, while the pelvis of Necrolestes is of the normal, undifferentiated insectivorous type. The femur, as Ameghino has pointed out, is extra- ordinarily peculiar, though not without a certain resemblance to that of Chrysochloris. The head is small, hemispherical and set upon a very short neck, presenting obliquely inward and forward, so that the head is invisible when the bone is viewed from behind ; the pit for the round ligament is exceed- ingly minute. The great trochanter is a thin, com- pressed ridge, which also presents forward as well as outward, with the digital fossa quite obsolete. The second trochanter is a small, compressed, pyramidal projection, and is connected with the great trochanter by a rough ridge, while the third trochanter is hardly more than indicated. The femoral shaft has its proximal position much twisted ; it is broad transversely, and compressed antero-posteriorly, while the distal portion of the shaft is very slender and of cylindrical shape. The distal end is moderately widened and the rotular trochlea is very broad and shallow, almost plane transversely, in fact. The con- dyles are very small, hardly projecting behind the plane of the shaft, and they are quite widely separated from each other. In Chrysochloris the femur is not altogether dissimilar to that of Necrolestes, but differs in many respects. The head is conspicuously larger and presents less forward ; the great trochanter is thicker and there Necrolestes patagon- ensis, left femur, x \. a. Front view. b. Hind view. 378 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. is an indication of the digital fossa ; the shaft is thicker and the condyles are much larger. In Notoryctes the femur is quite different from that of either of the other genera ; the head is large and presents directly inward ; the proximal end is much widened by the expansion of the great trochanter, which encloses a broad, shallow fossa on the anterior face of the bone, but there is no digital fossa or third trochanter ; the femoral shaft is short and straight. The tibia of Necrolestes is slender and elongate, though a little shorter than the femur. The proximal condyles are faintly marked and are sepa- rated by a very shallow groove ; there is no tibial spine. The anterior border of the proximal end of the tibia is raised into a crest, which makes this end decidedly concave in the antero-posterior direction, but there is no distinct cnemial crest. The shaft is slender and has a lateral sigmoid curvature, while toward the distal end it broadens slightly. The fibula is closely applied to the tibia, but does not coalesce with it at any point ; its proximal and distal ends are broad and thick and the shaft is slender, but not filiform. In Chrysochloris the leg bones are coossified ; the proximal end of the tibia has not the vertical crest which is characteristic of Necrolestes, but possesses a feebly marked cnemial process, which gives to this region of the shaft a more trihedral shape. In Notoryctes the leg bones are very peculiar ; the tibia has an immense cnemial crest, which runs nearly the whole length of the shaft and to which the relatively enormous patella is attached ; the shaft is short and straight, much compressed laterally, but made exceedingly thick antero-posteriorly by the great cnemial process. The fibula is free and is in contact with the tibia only at the two extrem- ities ; it also has the proximal end much expanded antero-posteriorly, while the shaft is stout and has a thickened distal end. Of the pes in Necrolestes only the calcaneum, astragalus and cuboid are represented. The calcaneum has a rather short and slender tuber, which is tapered toward the free end and is so curved as to be convex externally and concave internally, thus differing from both of the modern genera, in which the tuber is longer, stouter and quite straight. The astragalus has a neck which is directed strongly toward the mesial side of the foot, end- ing in a very small rounded head. The cuboid is very small, but of a shape not unlike that seen in Chrysochloris, which, however, much exceeds it in every dimension, especially in the proximo-distal length. So much INSECTIVORA OF THE SANTA CRUZ BEDS. 379 of the tarsus as is preserved displays but little resemblance to that of Chrysochloris. Among the loose bones associated with one of the specimens is one which much resembles the falciform bone which is attached to the tarsus in Notoryctes, but its reference is quite uncertain. Relationships. — The taxonomic position of Necrolestes would seem to be reasonably clear. It cannot well have had any direct connection with Notoryctes, because the latter is in every essential respect a marsupial, while Necrolestes is as distinctively one of the Insectivora. The presence of four upper incisors is no indication of marsupial affinities, since even in the modern Soricidce there are four incisors in the premaxillary. Though there are many resemblances between the South American and the Aus- tralian genus, it can hardly be doubted that these resemblances are due to convergence, as are also the many likenesses between Chrysochloris and Notoryctes. On the other hand, the similarites of Necrolestes to Chry- sochloris seem probably to be due to genetic relationship. This conclusion is justified not only because the resemblances between the two genera are so numerous and so close, but also because even the differences are, for the most part, such as usually occur between the earlier and later members of a phylum or of two allied phyla. The resemblances are to be found in all parts of the structure. The dentition is of very similar type in the two genera, especially the molars and the posterior premolars. The incisors and canines of Chrysochloris are modernized in a way that, as Leche has shown, has been frequently re- peated within the limits of the modern insectivorous families. Aside, perhaps, from the relatively large size of the canines, the dentition of Necrolestes is one from which that of Chrysochloris might readily have been derived. The same is true of the skull ; in most respects the skull of the African genus is much the more differentiated of the two. This is especially to be seen in the inflated condition of the temporal region in Chrysochloris, but the skull of Necrolestes is not far removed from what the ancestral type of the former probably was. The vertebrae of Necrolestes in all regions of the column are remarkably like those of Chrysochloris (except that the former had a much better de- veloped tail) differing from them in only a few details, while those of both genera are altogether unlike the characteristic vertebrae of Notoryctes. Imperfect specimens of the scapula resemble Notoryctes rather than 380 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. Chrysochloris, but the humerus is almost exactly as in the latter, as are also the forearm bones, even to the ossification of the flexor tendon. The manus is very much less reduced and specialized than in the African genus; the carpals, metacarpals and phalanges are present in nearly or quite their normal numbers and the digits were apparently five and of approximately equal size. The ungual phalanges are all of similar type, that of the third digit not being greatly enlarged, nor the others much reduced. It is evident that Necrolestes cannot have been so thoroughly well adapted to burrowing habits as is Chrysoc Moris, though the structure of the arm and forearm shows, that it was fossorial. Different as the manus is in the two genera, the plan of structure is the same in both and that of Chrysochloris may well have been derived from a type like that of Necrolestes. The pelvis of the Patagonian genus is not altogether unlike that of the African, but it is much less modified, as is to be seen in the large size of the pubes and of the obturator foramina. The hind leg and foot are, how- ever, quite peculiar and appear to have been specialized in a manner dif- ferent from that characterizing any of the modern families of Insectivora. Another consideration which renders it probable that Necrolestes itself, or its immediate ancestor, was an immigrant from Africa, is the entirely isolated position of this genus in the Santa Cruz fauna. Of course, it might have been the last remnant of a once numerous group, but no allies, or near relations, or probable ancestors have been found in any of the pre-Santa Cruzian formations. Had the family been a truly indigenous one, we should undoubtedly find a greater or less number of allied genera, as is the case with all the other orders represented in the Santa Cruz beds, but Necrolestes stands quite alone, a fact which is explicable only on the assumption that it is an immigrant. It is not suggested that Necrolestes is to be regarded as the ancestor of any of the existing Chrysochloridce, for it is itself specialized in a different, though moderate way. What does seem probable is that Necrolestes is an offshoot from some early member of the family which was at the same time the ancestor of Chrysochloris. If this conclusion is correct, it will lead to the further inference that the family originated in the Southern Hemisphere, and will militate against the view that the Cape golden moles are allied to the true moles. The resemblances, neither many nor close, between the two families are much more probably the results of INSECTIVORA OF THE SANTA CRUZ BEDS. 381 • adaptation to similar habits of life than to genetic relationship. The more the Santa Cruzian fauna is studied, the more clearly does it appear that these southern mammals are but very remotely connected with their analogues of the Northern Hemisphere. Rutimeyer's suggestion of a southern centre of origin and distribution becomes, with advancing knowl- edge, distinctly more probable than the view which regards all southern types as having migrated from the great northern centres of development. Another important corollary of the reference of Necrolestes to the Chrysochloridce is that it makes necessary, or at least probable, the assump- tion of a land connection between Africa and South America. There is no reason to suppose that the track 'of migration could have been by way of Europe and North America, for no trace of this family has ever been found in any of the northern continents. This supposed connection of Africa with South America has often been suggested before and is sup- ported by many independent lines of evidence. Into the discussion of this evidence it is not necessary to enter here, for it has lately been summed up by Lydekker ('96, 127, 255) and Tullberg ('99, 491) and must again be considered in the general statements concerning the Santa Cruz fauna as a whole. It may be pointed out, however, that the presence of Necrolestes in Patagonia is, so far as it goes, distinctly confirmatory of the hypothesis. NECROLESTES PATAGONENSIS Ameghino. (Plate LXIV, figs. 1-5.) Necrolestes patagonensis Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, P- 303- Though I have referred all the specimens in the collection to this spe- cies, it is not altogether improbable that more than one species is repre- sented among them. The type of N. patagonensis is a left mandibular ramus, lacking the coronoid and symphysial region. As already men- tioned, this individual is remarkable for the great size of the canine root, which is plainly divided into two, and rises so high above the alveolus as to raise the base of the crown above the tops of the grinding teeth. In the Princeton specimens the enamel-covered crown of the tooth descends into the alveolus, the root is much smaller, though there is some individual variation in this respect, and I cannot detect any division of it. If the peculiarities of the type are normal and not pathological, it will probably prove to be specifically distinct from the Princeton specimens. 382 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. Among the latter we find some indication of two types of skull, as was pointed out in the generic description. In one (PI. LXIV, fig. i) the skull is narrow and the snout is upcurved in a most curious fashion, being continued well in advance of the incisors and making the upper contour of the face strongly concave. The other skull (fig. 2) is broader, heavier, with nearly straight facial contours and, apparently, no great prolongation of the snout. The difficulty of determining whether these skulls are really as different as, at first sight, they seem to be, lies in the fact that the first has suffered hardly any distortion, while the second has been crushed ver- tically and the tip of the snout is somewhat broken. All the individuals agree well in size and indicate an animal of about the same size as Chrysochloris mllosa. MEASUREMENTS. No. No. No. 15,065. 15,384. 13,699. Upper dentition, length o 1 8 .017 " " " of incisor series 003 5 .004 " " " canine to m-S. 0125 .01 1 " " " of premolar series 0055 -0055 " " " of molar series OO35 .003 Upper canine, antero-posterior diameter at base 0025 .002 " " transverse " ooi 5 Lower dentition, length of incisor series .003 " " " canine to mj 014 .0125 " " " of premolar series 0055 .0053 •OOSS " " " of molar series 004 .0033 Lower canine, antero-posterior diameter 002 .002 .002 " " transverse " ooi 5 .001 Occiput, width at base 020 .020 Skull, length to Ji 03 5 " interorbital width o 1 2 " length, orbit to end of rostrum. " " " " jl 016 Zygomatic arch, length 0125 Palate, length 016 " width outside of p£ on " "ml 012 Mandible, length from condyle to canine 024 .0225 " " " angle to canine 0205 .0195 " depth at p^ 003 5 .003 Last seven trunk vertebrae, length .028 INSECTIVORA OF THE SANTA CRUZ BEDS. 383 No. No. Penultimate lumbar, length .................................... 004 " " width of anterior face ........................ 003 " " height to end of neural spine .................. 007 Sacrum, length .......................... . ................... 0109 Pelvis, length ............................................... 024 Ilium, length ............................................... 016 " greatest width ............................................ 0045 Humerus, length ............................................ 016 " proximal width ..................................... 005 5 " distal width over epicondyles .......................... oio " width of trochlea ................................... 006 Radius, length .............................................. 014 .0155 " proximal width ....................................... 003 .0035 " distal width .......................................... 003 .0033 Ulna, length ................................................ 023 " width at sigmoid notch .................................. 003 5 " distal width ........................................... OO2 .002 Metacarpal III, length ....................................... 003 " " proximal width ................................. 0026 " " distal width .................................... 0023 Digit III, ungual, length ..................................... .0065 " " " proximal width .............................. .0026 Digit IV, phalanx i, length .................................. .0005 " " " " proximal width ........................... .002 " " " 2, length .................................. .0025 " " ungual, length ..................................... .005 5 " " " proximal width .............................. .003 Femur, length from head .................................... .018 " great trochanter ........................... .018 " proximal width ...................................... .005 " distal width ....... ................. ' ................ .004 Tibia, length .............................................. .017 " proximal width ....................................... .0045 " distal width .......................................... .002 Fibula, length ............................................. .015 " distal width ......................................... .0015 Calcaneum, length ......................................... .0043 Astragalus, length ........................................... .003 " width of trochlea ................................. .0025 PART III. GLIRES. The rodent fauna of the Santa Cruz beds consists exclusively of Hystri- comorpha, a very marked contrast to the modern fauna of the same region, in which the Myomorpha predominate. All of the non-hystri- comorph rodents which now inhabit South America are of northern origin, their ancestors having reached South America not earlier than the close of the Miocene, when the great intermigration of the mammals of the two continents began. Confining our attention to the Hystricomorpha, we find that the Santa Cruz rodents are very closely allied to recent South American genera and are all referable to existing families and even, with one exception, to existing subfamilies. The richness and variety of this assemblage are surprising, for, except the Dasyproctidce and Dinomyidce, all the recent families are represented and the number of genera is comparable to that which is spread over the entire Neotropical region of to-day. It must not be supposed that the full number of Santa Cruz genera has been already discovered, though it is improbable that the list will be very greatly extended in the future ; for, from the large collections made by Messrs. Hatcher & Peterson for Princeton University and by Mr. Brown for the American Museum of Natural History, not a single new genus has been added to those described by Ameghino, and even of new species the number is very small. The general aspect of the Santa Cruz rodents is strikingly modern and a hasty examination might easily lead to the conclusion that they were essentially the same as the recent forms, but such a conclusion would be quite erroneous. The genera are all extinct and a considerable number of them have left no successors ; these latter are, for the most part, the more or less modified survivors of earlier faunas and, for that reason, are often of great phylogenetic importance. The subjoined table, which follows Thomas' arrangement of families and subfamilies ('96, 1015 ff.), will serve to give an idea of the compara- 384 GLIRES OF THE SANTA CRUZ BEDS. 385 tive number of the hystricomorph rodents of South America in Santa Cruz and in recent times. Recent. Ctenomys. Aconaemys. Spalacopus. Octodon. Abrocoma. Dactylomys. Thrinacodus. Kannabateomys. Loncheres. Thricomys. Cercomys. Carterodon. Mesomys. Echimys. Myocastor. Capromys. Plagiodontia. Coendou. Chaetomys. Wanting. Viscaccia. Chinchilla. Santa Cruz. I. OCTODONTID/E. i . Octodontince. Not found. 2. Loncherince. Stichomys. Adelphomys. Gyrignophus. Spaniomys. Graphimys. 3. Capromyince. Neoreomys. Scleromys. Lomomys. Olenopsis. II. ERETHIZONTID/E. 1. Erethizontince. 2. Chcetomyince. 3. Acaremyince. III. CHINCHILLID^E. Steiromys. Not found. Acaremys. Sciamys. Prolagostomus. Pliolagostomus. 386 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. Recent. Santa Cruz. Lagidium. Scotaeumys. Perimys. Sphodromys. IV. DASYPROCTID/E. Dasyprocta. Not found. Agouti. V. DlNOMYID/E. Dinomys. Not found. VI. CAVIID/E. Cavia. Eocardia. Kerodon. Schistomys. Dolichotis. Phanomys. Hydrochoerus. 29 20 The Santa Cruz rodents are, of course, somewhat more primitive in structure than their recent successors, but the difference is hardly so great as might have been expected. In most instances, the teeth have a some- what simpler pattern, but in others the modern pattern is fully attained and in a few cases surpassed. The skull structure is very nearly the same in the two faunas, with very minor differences. For example, the palate is rarely so extremely triangular as in many of the modern genera ; the coronoid process of the mandible is less reduced in size and the masse- teric crest is more normal in development. Limbs and feet are usually, but not always, relatively smaller and the ulna and fibula have under- gone little reduction. The number of digits is known in only a few of the Santa Cruz genera and in most of these the formula is V-V, but in the cavies the number IV-III is already characteristic. From a phylogenetic point of view the Santa Cruz rodents are of much interest. In several of the genera, there is every reason to believe, we have the direct ancestors of existing forms : for example, l^iscaccia was prob- ably derived from Prolagostomus, Dolichotis from Schistomys, Rrethizon and Coendou from Steiromys. Several other genera may also be regarded as probable ancestors of recent types, but are still too incompletely known for any definite determination of their relationships. Thus, Scotceumys is the probable forerunner of Chinchilla and Lagidium, and the modern GLIRES OF THE SANTA CRUZ BEDS. 387 Loncherinae have no doubt descended from those of Santa Cruz times, but the latter are not yet sufficiently well known for us to distinguish the ancestral from the collateral forms. It is surprising that Ctenomys, now one of the most abundant and characteristic of Patagonian rodents, should have no Santa Cruz representative. Another group of Santa Cruz genera comprises certain specialized types which did not persist to a later epoch. Prominent among these are Acaremys and Sciamys, which Ameghino has very properly grouped to- gether as a subfamily of the Eretkizontidce. The numerous species of these two genera are all very small and some of them minute, superfi- cially like the rats and mice whose place they filled in Santa Cruz times, when South America possessed no representatives of the Myomor- pha. In these animals the molar pattern is like that of the tree-porcu- pines, but the skull, limbs and feet are quite different and indicate that their habits were probably terrestrial. Still a third category of genera, already alluded to, includes those rodents which, though not ancestral to any of the existing types, are yet phylogenetically important, because they have preserved, with more or less modification, the ancestral forms of. an earlier epoch. Neoreomys is an example of this ; on the whole, it resembles Myocastor and Capromys more than any other recent genera and is therefore included in the same subfamily, but the likenesses to the Dasyproctidce and Dinomyidce are also very suggestive and indicate that this genus is not far removed in structure from some earlier and more generalized form, which was the common ancestral stock of several distinct families. Another instance of the same kind is afforded by Perimys, the Santa Cruz species of which are not ancestral to any modern rodent, or to any yet known from intermediate formations, but they probably differ little from some earlier genus that formed the common stock whence all the Chinchillidce were derived. Although most and probably all of the existing South American families of Hystricomorpha had already become distinctly separated as such, and even the subfamilies are more or less clearly defined, yet the separation is not so great as between the existing representatives of the same groups. There is more uniformity in dental pattern and in the structure of the skull and skeleton than we find at present, and the various families are evidently converging backward in time to a common ancestry. This is strong evidence for the unity of origin of all the Hystricomorpha, or, at 388 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. least, of all the South American families of the suborder. It will, I think, be eventually possible to prove that all the varied molar patterns of the existing genera have been derived, now by simplification, again by increased complication, from a pattern which is nearly exemplified by the genera Luanthus and Cephalomys of the Patagonian beds. This conclusion agrees in a general way with the results of Winge ('87, 128) who assumes that the grinding teeth were early complicated by the formation of four more or less complete, transverse folds, though I should regard three as the more probable number of such folds. Tullberg, on the other hand, does not accept this conclusion : "Mehrere Griinde lassen es meines Erachtens einfacher erscheinen, fur die Back- zahne der Hystricomarphen eine allmahliche und bei den verschiedenen Formen selbstandig je nach Bedarf eintretende Komplizierung auzuneh- men. Es 1st natiirlicherweise nicht unmoglich, dass Falten bei dieser oder jener Form, welche deren mehrere an jedem Zahn besass, reduziert worden sind. Daraus diirfte indes keineswegs zu folgern sein, dass die urspriinglichen Hystricomorphi ebenso zahlreiche Falten gehabt hatten, wie Z. B. die Erethizontiden. Falls man dieses behauptete, miisste man namlich annehmen, dass die Falten bei Cavia und Dolichotis reduziert, aber bei Hydrocheerus an Zahl vermehrt, bei Petromys und Aulacodus und dieses ebenfalls bei alien Eckinomyiden, Myopotamus ausgenom- men, reduziert worden waren " ('99, 365). So far as the cavies are concerned, the assumption which Tullberg regards as so improbable is demonstrably true. It will be shown in a sub- sequent chapter that in Schistomys, which is almost certainly the direct ancestor of Dolichotis, the unworn teeth have three transverse enamel folds, in addition to the principal valley between the prisms. These folds are soon converted by abrasion into enamel lakes and in the fully adult animal they are entirely worn away, leaving the teeth exactly like those of Dolichotis. In Luanthus, of the pre-Santacruzian, or Patagonian beds, the pattern of the teeth is the same as in Schistomys, with the important exception that the enamel folds are deeper and the teeth are rooted. Here, then, we have clear evidence that in Dolichotis, at least, the exist- ing type of tooth has been acquired by simplification. The Santa Cruz rodent fauna throws no light whatever upon the prob- lem concerning the relationships of the Hystricomorpha to the other rodent suborders. For this purpose the fauna is of much too late a period to be GLIRES OF THE SANTA CRUZ BEDS. 389 available, and only the fuller knowledge of the pre-Santacruzian rodents can lead to definite results. HYSTRICOMORPHA. OCTODONTID^.. CAPROMYIN^. NEOREOMYS Ameghino. (Plates LXIV, Figs. 6-6"; LXV, Figs, i-n ; LXX.) Neoreomys Amegh. ; Enumeracion systematica, etc. ; 1887, p. 10. Pseudoneoreomys Amegh. ; Rev. Argent, de Hist. Nat; T. I, 1891, p. 300. This genus includes the most abundant of the Santa Cruz rodents, and its species are among the largest in size. The teeth are quite similar to those of the recent Myocastor (Myopotamus] though somewhat simpler in pattern and without cement in the valleys. On the other hand, the skull is much more like that of Capromys, with certain distinct resemblances to that of Agouti (Coslogenys}. Dentition. — The incisors are broad and heavy, with nearly plane or very slightly convex anterior faces and sometimes with a very faintly marked groove near the external border ; they differ in proportions from those of .Myocastor. The grinding teeth vary greatly in appearance according to age and amount of wear. The single premolar in each jaw is erupted very late, not until the last molar is in use. In the unworn state pA (Plate LXV, fig. i) is divided into three laminae by oblique furrows, which are directed inward and backward across the masticating surface ; at the end of the anterior valley, near the antero-external angle of the crown, is an isolated enamel pillar. In the moderately worn state of this tooth the crown is columnar, undivided by sulci, with oblique enamel lakes, indi- cating the course of the original enamel folds or valleys, of which the posterior is the smallest. Ameghino has distinguished two genera in accordance with the number of these lakes, Pseudoneoreomys with three, and Neoreomys with a fourth, produced by an internal fold. Probably this difference is merely a matter of abrasion and is determined by the mode in which the original three folds are subdivided by wear. 39° PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. The upper molars are somewhat more complex ; in unworn teeth the crown is similarly composed of three oblique laminae, of which the median one is the longest and the posterior the shortest, and the latter is subdi- vided into two parts by a shallow, transverse groove ; of these two parts, the inner one has a pocket-like depression of enamel on the posterior side. In the condition of wear which characterizes the adult animal, and which most specimens display, the crown of an upper molar is divided by a deep internal fold into two triangular prisms, of which the anterior one is considerably the larger ; the outer end of the foremost valley soon becomes isolated as an enamel lake, while the outer end of the posterior valley is also separated from the inner end and remains for some time as an external enamel fold, but in the fully y ^ adult animal it is separated from the outer wall of Grinding teeth of the crown. The tooth then has a deep internal fold Myocasior coy pus, and three enamel lakes. Of these the anterior one is crown view, x{. a. originally a part of the deep inner fold, which has an Right upper teet . o^jjque course but its outer portion is soon separated b. Right lower teeth. . . to form a lake. A fourth very minute lake is formed by the isolation of the enamel pocket, mentioned above as impressing the posterior side of the hindmost lamina. This minute lake disappears at quite an early stage, so that many teeth show no trace of it. Aged ani- mals, in which the teeth are much worn, lose even the inner fold, which is first converted into a lake and then obliterated. In the lower jaw the grinding teeth have a similar character, but are reversed, the deep fold which divides the crown into two prisms being external, and the posterior one of the three lakes is an isolated portion of this fold. All the folds are somewhat shallower than in the upper teeth and hence are sooner cut off from the peripheral wall by abrasion. All of the grinding teeth diminish in diameter toward the base, so that their size is reduced by wear ; especially is this true of mT, which is the first of the permanent lower teeth to be erupted and in an advanced state of wear appears to be quite disproportionately small. Milk Dentition. — I have seen no example of the temporary incisors, which are probably shed very early. On the other hand, the milk premolar is frequently found, but in most cases is so much worn that its pattern is not clearly displayed. Plate LXV, fig. 3, shows an isolated tooth which I GLIRES OF THE SANTA CRUZ BEDS. 391 regard as dp- of this genus, although it is considerably larger than in most individuals ; its relatively large size is due to the small degree of abrasion which it has suffered, for it contracts much toward the base, especially in the antero-posterior diameter. DpT I have not found in so early a stage and the youngest example is that shown in Plate LXV, fig. 6 ; the tooth is still very large, but already has well developed roots ; the grinding surface displays one wide and deep external fold and two FIG. 38. Skulls of Octodontidae, side view. a. Myocastor coy pus, x |. b. Capromys fournieri, x J. c. Neoreomys australis, x f . narrower and shallower internal folds ; in addition to these, the anterior prism has two enamel lakes, of which the antero-external is larger and crescentic in shape, and the postero-internal is very minute. As a whole, the dentition resembles that of Myocastor, though the molar pattern is distinctly less complex ; that of Capromys is nearly as simple as 392 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. in the fossil, and the teeth of Agouti, especially the lower molars, might readily be derived from the Neoreomys type. Skull (Plate LXIV, fig. 6). The skull is more like that of Capromys than that of Myocastor, though with many resemblances to that of Dasyprocta. In general proportions and appearance, this skull might be described as intermediate between Capromys and Dasyprocta ; the peculi- arities of the Myocastor skull are not foreshadowed in Neoreomys. As a whole, the skull is long and narrow, much as in Capromys ; compared with that of Dasyprocta, the cranium is relatively longer, the orbit con- spicuously smaller, and the rostrum shorter, lower and less tapering. The proportionate lengths of the parietal and frontal zones are much as in Capromys, but there is a short and well defined sagittal crest on the hinder half of the parietals. The occiput (Plate LXIV, fig. 6C) is not unlike that of Myocastor, aside from the altogether exceptional character of the paroccipital and mastoid processes in the latter; it is low and wide, slightly concave and with distinct median ridge; the foramen magnum is high and narrow, as in Myocastor, differing from Capromys and Dasyprocta, in which the prin- cipal diameter is transverse ; the paroccipital processes have about the same relative development as in the last-named genus, but are more closely applied to the large tympanic bullse. The supraoccipital is ex- tended much farther upon the roof of the cranium than in Myocastor or Capromys and differs notably from these genera in having no lateral pro- cesses, and not extending down over the periotic, from which it is sepa- rated by the supramastoid process of the squamosal. The tympanic and periotic are not unlike those of Dasyprocta, but have a still closer resem- blance to those of Cavia; the periotic is quite extensively exposed on the side of the cranium, but the ascending process is narrower and the mastoid process is hardly more distinct than in the latter genus. The tympanic is inflated into a large bulla and coossified with the periotic ; the auditory meatus is a short, incomplete tube, with ventral slit opening into the central hole in the outer wall of the bulla almost exactly as in Dolichotis. The squamosal differs in several particulars from that of Myocastor ; anteriorly, it does not extend so far along the frontals, being more as in Capromys in this respect, while the supramastoid process, is considerably broader than in either of the genera named. The zygomatic process most resembles that of Myocastor, but extends less outward and more down- GLIRES OF THE SANTA CRUZ BEDS. 393 ward ; the two glenoid cavities are almost parallel, converging forward but slightly. The jugal is quite similar in shape to that of Myocastor, but is much narrower ; anteriorly, it ends in a concave suture for the zygomatic process of the maxillary, and does not ascend upon that process. A marked difference from the last-named genus and Capromys is furnished by the lachrymal, which is quite large and forms most of the anterior border of the orbit, while in the two modern genera this bone is reduced to rudi- mentary proportions. The frontals are rather short, quite broad, and nearly plane, showing FIG. 39. Skulls of Octodontidae, top -view. a. Myocastor coypus, x |. b. Capromys fournicri, x \. c. Ncorcoinys anstralis, x f . • no external indications of sinuses ; no well defined temporal ridges are present, but the postorbital processes are quite prominent and in front of each process the projecting supraorbital border is notched. The nasals are of nearly the same relative length as in Capromys, but are less convex transversely ; they are broad, widening somewhat forward ; the anterior end of each nasal has a broad, shallow, lateral notch, much as in Myo- castor, while the hinder ends together form a single convex curve, which fits into a concavity of the frontals. The anterior nares are not unlike 394 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. those of the last named genus in shape, but are lower and wider. The premaxillaries are shorter than in Myocastor or Capromys and their ven- tral edentulous surface is broader ; the long, narrow, incisive foramina are more as in the latter genus ; the frontal processes are longer and narrower than in either. The maxillaries are lower vertically than in Myocastor, in correlation with the less completely hypsodont teeth ; the infraorbital foramen is lower and wider, and of quite a different shape, and has no groove for the nerve ; the preorbital fossa is much more deeply impressed, as in Dasyprocta, an- other resemblance to which is the large size of the lachrymo-nasal open- ing. The bony palate is considerably wider than in Myocastor, especially at the anterior end, the two series of upper teeth converging less forward. The palatines are longer, extending forward to the middle of m1, and the posterior palatine foramina notch the palatines more deeply, so as to be almost entirely enclosed in them. The posterior nares are narrower and more elongate than in Myocastor, extending almost to the middle of m1, with a short, sharp, median spine on the anterior border. The pterygoids are not well preserved in any of the specimens, but apparently the fossa did not communicate with the orbit; it is, however, connected with the posterior nares by a round aperture, bounded ventrally by an extension of the pterygoid, which joins the bulla, somewhat as in Dasyprocta. The mandible is very different from that of Myocastor and might be described as intermediate in character between that of Capromys and that of Dasyprocta. The horizontal ramus is short and heavy ; the masseteric ridge is quite well developed, but is less prominent than in Myocastor or Capromys; on the other hand, the pterygoid ridge is much more promi- nent than in Dasyprocta, making the ventral border of the angle much wider; in none of the specimens is the angular process complete, but it would appear to have been shorter than in any of the three recent genera named. The coronoid process, which in Myocastor has almost disap- peared, is much higher than in the other two genera mentioned, rising as high as the condyle, from which it is separated by a deep and narrow sigmoid notch; the process is also quite broad, especially at the free end; at the base of the coronoid is a small, but well defined, masseteric fossa ; the condyle is large and convex, in shape quite like that of Myocastor, but a resemblance to Dasyprocta may be seen in the thin, plate-like extension behind the condyle, though this extension is considerably shorter and has GLIRES OF THE SANTA CRUZ BEDS. 395 a more steeply inclined dorsal border than in the modern genus. The inferior dental foramen has the same position as in Myocastor. Vetebral Column and Ribs (Plate LXX). — Except for the cervical and some of the lumbar vertebrae, the backbone is represented by very unsat- isfactory material and the vertebral formula is largely conjectural. The neck is short, but relatively stout, its proportions being not .unlike those of the neck in Agouti. The atlas most resembles that of Capromys ; it is short, broad and depressed, with low and wide neural canal ; the neural spine is a prominent tubercle and there is a distinct hypapophysis ; the transverse processes are very different from those of Myocastor, resembling rather those of Agouti, except that they are considerably shorter. The axis has a neural spine which is quite like that seen in Capromys and Myocastor, but it is produced more obliquely upward and less backward ; the centrum, which is keeled ventrally, is very broad and depressed an- teriorly, becoming much narrower behind the transverse processes, which are short and slender. The remaining cervicals are not especially char- acteristic ; they have short and depressed centra, with very oblique faces, and short neural spines, of about the same relative size as in Agouti; the transverse processes, on the other hand, are much smaller and the " inferior lamella" is distinct only on the sixth. The number of trunk vertebrae is very uncertain, but there is reason to believe that the formula is not far from Th. 13, L. 6. In the anterior thoracic region the vertebrae are small, with slender neural spines inclined strongly backward ; the spine of the second thoracic appears to have been considerably stouter than that of the first or the third, but not to any such disproportionate extent as in Myocastor. Posteriorly the vertebrae be- come much larger, gradually assuming the character of the lumbars. In the latter, the centra are long and heavy, with ventral keels and expanded, depressed faces, and have long, broad and laterally compressed neural spines, much resembling those of Agonti in shape and, as in that genus, strongly inclined forward ; the prezygapophyses are very prominent, but the metapophyses»are small and do not rise conspicuously above them; the anapophyses are likewise small, a striking contrast to Myocastor, in which these processes are remarkably long and prominent. The trans- verse processes are not complete in any of specimens and their length cannot be determined, but so far as they are preserved, they resemble those of Agouti; in fact the lumbars are decidedly more similar to those of the latter than to those of Myocastor. 396 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. Only fragments of the sacrum have been recovered, enough, however, to show that the spines were long and separate, not fused into a contin- uous ridge. Nothing is known of the caudal vertebrae, but the fragments of the sacrum indicate that the tail was probably long and well developed. The ribs likewise are represented by more or less fragmentary remains, which appear to be shorter, more slender and less curved than in Myo- castor, and to have rather more resemblance to those of Agouti; the anter- ior ribs are broader and more compressed laterally, the posterior ones more slender and rod-like. The sternum is entirely unknown. Appendicular Skeleton. — The scapula is high and rather narrow, with slender neck and no coraco-scapular notch ; the spine appears to be nearly in the middle and to divide the blade into almost equal pre- and post- scapular fossae, the former perhaps somewhat broader. (In the restoration, Plate LXX, the scapula is incorrectly restored, the prescapular fossa being made too narrow and the coracoid border forming too definite an angle with the suprascapular. Probably the shape was more like that seen in Agouti.'] A very marked difference from Myocastor and Capromys con- sists in the shallowness of the notch, "incisura colli," which determines the length of the acromion ; in the two recent genera this notch is ex- tremely deep, while in the fossil it is much shallower, as is clear, despite the fact that in none of the specimens is the acromion preserved, for the distal extension of the spine is shown. The coracoid, though hardly vis- ible from the side, is yet quite large, forming a slender, incurved hook. In the humerus also we find greater resemblance to Agouti than to Myocastor; the shaft is relatively long and, for most of its length, is strongly compressed laterally ; its thickness, which is considerable in the proximal portion, diminishes distally ; the deltoid hook, so conspicuous in Myocastor and Capromys, is entirely absent ; the trochlea is broad and, anteriorly at least, is covered entirely by the radius and consists of three parts, a narrower external and broader internal concavity and a pro- nounced convexity between them ; there is, however, no interruption of the articular surface. The supratrochlear fossa is large and deep and is perforated by a fontanelle, while the anconeal fossa is smaller ; the epicon- dyles are very inconspicuous and there is no entepicondylar foramen. The fore-arm bones are of moderate length, the ulna about equalling the humerus in this respect, and they are thus somewhat shorter than in Myocastor. The radius has a broadly expanded head, which occupies the GLIRES OF THE SANTA CRUZ BEDS. 397 whole width of the humeral trochlea ; the shaft is quite stout, antero-pos- teriorly compressed and of transversely oval cross-section, and has a de- cided forward curvature. The ulna has a relatively short olecranon, much as in Capromys, a very broad coronoid process and a wide sigmoid notch, which articulates with the posterior side of the humeral trochlea ; the shaft is quite stout, laterally compressed and arched forward, with an obscure channel on the outer side of the proximal portion. Nothing is known of the carpus and very little of the metacarpals and phalanges, which are represented by very fragmentary material. It is apparent, however, that the manus is somewhat larger and heavier in pro- portion to the pes than is the case in Myocastor. A single imperfect ungual phalanx resembles that of Agouti, being more depressed and less pointed than in the former, and, seemingly, having no cleft at the tip. The pelvis is elongate ; the ilium has a broad and ill-defined peduncle, which expands quite abruptly into the anterior plate ; this anterior expan- sion is quite unlike the trihedral ilium of Myocastor, having somewhat more the shape seen in Capromys, but is considerably broader than in the latter; a resemblance to Agouti is in the prominent development of the ilio-pectineal process, as also in the division of the gluteal surface by a distinct longitudinal crest. The ischium is incomplete in all of the spec- imens ; so far as preserved, its post-acetabular portion is quite slender and laterally compressed, slightly increasing posteriorly in the dorso-ventral diameter ; the obturator foramen is evidently large. , The femur is large, much surpassing the humerus both in length and thickness ; the head is rather small and set upon a constricted neck, and the great trochanter is thick and heavy, but rather short, making the notch between itself and the head no deeper than in Capromys ; the digital fossa is large and very deep ; the second trochanter is much reduced and there is no trace of the third. The shaft is stout and somewhat compressed laterally ; the distal end is heavy, though the condyles are not prominent ; the rotular groove is narrow, but has elevated borders and is continued very far dorsally, resembling that of Agoidi. The patella is quite large, especially in width, but antero-posteriorly compressed and with a small diameter in that direction ; it thus differs much from the massive patella of Agouti and is more like that of Capromys. The tibia is not ankylosed with the fibula and is a very heavy bone, of almost the same length as the femur ; proximally, the shaft is trihedral, 398 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. becoming transversely oval distally ; the cnemial crest is not very prom- inent, but extends very far down the shaft, which is much straighter than in Myocastor. The distal end is not much broadened, but is quite thick and heavy, and the distal fibular facet is extremely small ; the astragalar surface is deeply grooved and asymmetrical, the outer concavity much exceeding the inner in size ; on the posterior side is a very long and prominent intercondylar tongue. Little of the pes is preserved, but apparently it was relatively somewhat less heavy and elongate than in Myocastor. The astragalus has a well grooved, asymmetrical trochlea, the outer condyle much exceeding the inner in size ; the neck is quite narrow and depressed, ending in a convex head, upon the tibial side of which the navicular facet is reflected ; the external calcaneal facet is very large, deeply concave and so oblique as to reduce the fibular surface to a narrow band ; this external calcaneal facet is quite widely separated from the narrow sustentacular facet. The calcaneum is incompletely known, the tuber not being preserved in any of the specimens, but it evidently had a large dorso-plantar diameter and was laterally compressed ; the external astragalar facet is large and convex and the prominent, heavy sustentaculum bears a small subcircular facet. The distal portion of the calcaneum is elongate and ends in a very oblique concave surface for the cuboid. Fragments of the metatarsals indicate that those bones were shorter and heavier than in Myocastor. Restoration (Plate LXX). — Among modern genera it is the skeleton of Myocastor which displays the greatest resemblance to that of Neoreomys, but there are many differences. In the fossil, the head is smaller and lighter, while the shorter incisor teeth, paroccipital processes and angular processes of the mandible give to the skull quite a different appearance. The neck is more elongated and slender, but the vertebrae of the trunk are quite similar ; the long tail, shown in the figure, is entirely conjectural and may perhaps be incorrect. The limbs are somewhat longer tandheir pro- portions, as well as those of the feet, are rather more like those seen in Agouti than those of Myocastor. Relationships. — It does not seem at all probable that Neoreomys was directly ancestral to any existing genus. While it resembles the Capro- myince in dentition and skull structure rather more than any other recent rodents, it has also many likenesses to Agouti, Dasyprocta and Dinomys. GLIRES OF THE SANTA CRUZ BEDS. 399 It is exceedingly difficult, if not quite impracticable, to determine which of these similarities are due to genetic relationship and which of them to convergent development. On the whole, it seems probable that in Neor- eomys we have the somewhat modified remnant of a more ancient group, which was the common ancestor of the three families indicated. NEOREOMYS AUSTRALIS Ameghino. (Plates LXIV, figs. 6-6" ; LXV, i-ii ; LXX.) Neoreomys australis Amegh.; Enumeracion sistemat, etc., 1887, p. 11. Neoreomys ind^ms^^s Amegh. ; Ibid. Pseudoneoreomys leptorhynchus Amegh. ; Rev. Argent, de Hist. Nat. ; T. I, 1891, p. 300. Pseudoneoreomys mesorhynchus Amegh.; Ibid., p. 301. This is by far the most abundant and best known species of the genus and from it most of the preceding generic description has been taken. In size, the species is very variable, some individuals much surpassing others in this respect. Much of this variation is, however, due to differences of age, as growth evidently continued till a comparatively late period of life, and every stage of transition between the extremes may be observed. The teeth, on the other hand, are quite constant, except as their form and size are altered by abrasion. , The incisors have slightly, but distinctly, convex faces and pT has no groove upon the outer side of the anterior prism. In the following table, Nos. 15,222 and 15,396 are young individuals, 15,572 and 15,365 adult, while 15,266 was an old animal with much worn teeth. MEASUREMENTS. No. No. No. No. No. Upper dentition, length 15,222. OC2 I5,396- 15,572. .CK6 15^65. 15,266. .CK6 " " « pA-mi O2 1 .024. .023 Upper incisor width OCK .001 .00? " " thickness OO5 .004"; .00? Lower dentition length .O^O .048 .CKO " " " PT-mT . .O2S .O2i; .027 Skull length in median basal line . . . 081; .006 " " over all . .004. .102 .103 400 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. No. No, No. No. No. 15,222. 15396. 15,572. 15365. 15,266. Cranium, length, occipital condyle to rim of orbit .056 Face, length, orbit to end of rostrum. . . . .048 Occiput, height .030 " width at base .039 Skull, width behind zygomatic process . . .039 .040 " in interorbital region .030 -032 Rostrum, width at anterior end 019 .018 .021 Mandible, length from condyle .068 .070 " depth below mT .013 .014 .01 5 NEOREOMYS PACHYRHYNCHUS (Ameghino). Pseudoneoreomys pachyrhynchus Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 300. Certain skulls in the collections are so large and heavy that they prob- ably represent a species different from the preceding one, especially as they are not closely connected by transitional forms with the average in- dividuals of N. australis. To these large animals the name N. pachy- rhynchus Amegh., may be applied, as the broad and heavy rostrum is a very characteristic feature. The type specimen appears to be rather smaller than the somewhat crushed and distorted skull in the collection of the American Museum of Natural History (No. 9,130) from which the following measurements are taken. The type is, however, so incomplete as to permit little direct comparison. MEASUREMENTS. Upper dentition, length 059 Occiput, height 03 2 " " pA-mi 024 " width at base 040 Upper incisor, width 006 Skull, width behind zygomata 044 " " thickness 006 " " in interorbital region 036 Skull, length over all 109 Rostrum, width at anterior end 028 There remain two species of Neoreomys, which Ameghino has described and which are probably valid, though as each is known only from the type specimen, it is possible that they are merely abnormal individuals. NEOREOMYS DECISUS, Ameghino. Neoreomys decisus Amegh. ; Enumeracion sistemat., etc. ; 1887, p. 11. In size this species is much the same as N. australis, from which it is distinguished by the lower incisor. This tooth has a plane, instead of GLIRES OF THE SANTA CRUZ BEDS. 40 1 convex, anterior face and near the mesial border are two faintly marked, longitudinal grooves. NEOREOMYS VARIEGATUS Ameghino. (Plate LXV, Fig. 12.) Neoreomys variegatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pat- agonie, 1894, p. 68. The distinctive character of this species is to be found in pT, of which the anterior prism has a well denned vertical groove on the outer side, a feature which is not present in any of the other species. Size as in N. australis. SCLEROMYS Ameghino. (Plate LXV, Figs. 13-15.) Scleromys Amegh. ; Enumeracion sistemat., etc., 1887, p. n. Neoreomys Amegh. ; in part. This genus is much like the preceding one, from which it is distin- guished by its smaller size and by the simpler pattern of the grinding teeth. Individuals of Scleromys are quite rare and it is far less completely known than Neoreomys ; not even a well preserved skull has yet been found and the skeleton is entirely unknown. The incisors resemble those of Neoreomys in character, but are slightly broader in proportion to the length of the grinding series ; the anterior faces are more or less convex and have a crepe-like surface, produced by faint, wavy longitudinal striations. The upper grinding teeth are divided into two prisms by a deep internal fold, which extends obliquely across the crown almost to the external wall ; on more advanced wear the outer part of this fold is separated as a lake. A second and much shallower fold invades the posterior prism from the outer side, but is very early isolated as a lake. In advanced stages of wear even the internal fold loses its connection with the peripheral enamel and then the crown has three lakes, an anterior transverse pair formed from the internal fold, and a posterior lake derived from the external fold. In the lower teeth the pattern is, as usual, reversed, the principal enamel fold being external and posterior, and the secondary fold internal and posterior. So far as the skull is known, it is much like that of Neoreomys, with certain characteristic differences. The parietal region of the cranium is 402 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. broader and more flattened, contracting posteriorly to a short, narrow sagittal area, without trace of a sagittal crest. The palate is distinctly wider and the posterior narial opening conspicuously so, not only pro- portionately, but actually, and is of a somewhat different shape, the front border of the opening being more regularly curved and without median spine. The incisors extend farther into the maxillaries, the preorbital por- tion of which is relatively somewhat longer than in Neoreomys. From all the known material, it seems sufficiently evident that Scleromys is closely allied to Neoreomys. Ameghino has suggested ("94", 69) that it is ancestral to Ctenomys, but the character of the teeth seems to forbid such an association, while the skull is of quite a different type. SCLEROMYS ANGUSTUS Ameghino. (Plate LXV, Figs. 13, 14.) Scleromys angustus Amegh. ; Enumeracion sistemat, etc., 1887, p. n. ? Neoreomys limatus Amegh.; Revist. Argent, de Hist. Nat, T. I, 1891, p. 142. The type and possibly the only species. It is distinguished by its somewhat smaller size and more slender proportions, and by the more convex faces of the incisor teeth. The type of Neoreomys limatus is a mandible with much abraded teeth ; it is apparently referable to the present species, with which it agrees in size. In the subjoined table the dimensions of the upper jaw are taken from a palate, with teeth, in the collection of the American Museum of Natural History (No. 9,304) and those of the lower jaw from a specimen in the Ameghino collection. MEASUREMENTS. Upper dentition, length 044 Palate, width at pi 006 " " " pi-mi 018 " ", "ml 012 " " " mi-mi 013 Lower dentition, length 035 Upper incisor, width 004 " " " p^-m^ 020 " " thickness 0043 " " " mT-nij 013 SCLEROMYS OSBORNIANUS Ameghino. (Plate LXV, Fig. 15.) Scleromys osbornianus Amegh., Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 69. GLIRES OF THE SANTA CRUZ BEDS. 403 To this species Ameghino refers an imperfect skull and a mandible, which apparently belong to different individuals, without indicating either as the type. The skull is larger and more robust than that of S. angustus, though the length of the grinding series is the same, or but little greater ; the incisors also are somewhat flattened. MEASUREMENTS. Upper dentition, length pA-mi 018 Lower dentition, length p^-m^ 022 " ml-m^ 013 " " " mT-mj 016 Upper incisor, width 004 There remain two interesting, but very incompletely known genera, the position of which within the family is uncertain, though the molar pattern renders probable the reference of them to the Capromyince. These genera differ from all other known Santa Cruz rodents in having but three grind- ing teeth. LOMOMYS Ameghino. Lomomys Amegh. ; Rev. Argent, de Hist. Nat; T. I, 1891, p. 301. Neoreomys Amegh. ; in part. From the position of the upper teeth in the jaw and their relation to the posterior nares and to the zygomatic process of the maxillary, it is probable that the dental formula should be written p£ m£. The molar pattern resembles that of Scleromys, with two principal enamel folds, an anterior one from the inner side and a posterior one from the outer side, with a minute enamel lake lying behind the latter. In the unworn state m-3. appears to be composed of three transverse laminae. The two dental series pursue an almost parallel course, without marked anterior con- vergence. The hard palate, which is of nearly uniform width, is short and antero- posteriorly convex, rising steeply opposite m1 ; the posterior palatine for- amina are in the palatine bones. The only known species is LOMOMYS INSULATUS Ameghino. (Plate LXV, Fig. 27.) Neoreomys insulatus Amegh.; Contrib. al Conoc. Mam. Fos. de la Repub. Argent; 1889, p. 138. 404 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. Lomomys evexus Amegh. ; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 301. Lomomys insulatus Amegh. ; fenum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 69. Size a little smaller than Scleromys angustus, the upper grinding series measuring 13.5 mm. in length; the molars diminish gradually in size from m1 to m-. OLENOPSIS Ameghino. Olenopsis Amegh. ; Contrib. al Conoc. Mam. Fos. de la Repub. Argent. ; 1889, p. 145. Of this rare genus I have seen no Santa Cruz examples, but only a cast of the Parana species, O. typicus, which has dpT in place, with pT showing beneath it ; the dental formula is thus pT m¥. In the unworn state the molars are composed of three transverse and somewhat oblique laminae, of which the middle one is the longest; the folds contain thin deposits of cement. On wear, the enamel folds are isolated from the peripheral enamel and form lakes. OLENOPSIS UNCINUS Ameghino. Olenopsis uncinus Amegh. ; Contrib. al Conoc. Mam. Fos. de la Repub. Argent; 1889, p. 145. Characterized by the broad incisors, which have convex faces, and by the comparative simplicity of m¥, which is similar in pattern to mT, whereas in the later O. typicus, from the Parana beds, it is more complex. In size, O. uncinus is comparable to Neoreomys australis. LONCHERIN^E. In addition to the foregoing genera, which are, for the most part, com- paratively large animals, the family was represented in Santa Cruz times by a number of smaller rodents, some of them extremely small, in which the grinding teeth are shorter-crowned and have distinct roots. As yet, these genera are known almost entirely from the teeth, imperfect skulls of Stichomys and Spaniomys only having been found and nothing has been learned of the skeleton. The upper grinding teeth have one internal and two or more external folds of enamel, the number of the latter differing in each genus ; in the lower teeth the pattern is reversed, or it may be somewhat simpler. GLIRES OF THE SANTA CRUZ BEDS. 405 In molar pattern, the genera of the subfamily form a continuous series of increasing complexity, which may be tabulated thus : A. Lower grinding teeth with two internal folds. a. Incisors with convex faces Stichomys. b. Incisors with plane faces Adelphomys. B. Pj and m-j- with three internal folds, m^ and y with one Gyrignophus. C. Py, mT and 7 with three internal folds, my with one Spaniomys. D. My— y with three internal folds, p^- unknown Graphimys. STICHOMYS Ameghino. (Plate LXV, Figs. 16-20°.) Stichomys Amegh. ; Enumeracion sistemat, etc.; 1887, p. 10. This genus comprises small rodents, with rooted molars and narrow incisors, of which the thickness exceeds the breadth and of which, except in one species, the anterior faces are strongly convex. The size of the grinding teeth varies considerably with age, diminishing and becoming more uniform as abrasion advances. The molar pattern is simpler than in the other genera of the subfamily, Adelphomys excepted. In the upper jaw the teeth have each one deep and narrow enamel fold from the inner side and nearly opposite to this a corresponding external fold, the two being connected in unworn specimens ; in front of the principal external fold is another and somewhat shallower fold from the outer side, and in quite unabraded teeth is probably a third, posterior external fold. I have seen no specimen, however, in which this hindermost valley is not already converted into a lake. As abrasion increases, the anterior fold first be- comes isolated and finally even the principal internal and external folds are cut off, the peripheral enamel becoming continuous and enclosing four lakes. The lower molars are somewhat simpler in pattern, having one external and two internal folds and lacking the posterior fold of the upper teeth. I have seen no example of the milk teeth ; dp4 was prob- ably shed very early, as the premolar is always the most worn of the permanent teeth. The skull is very incompletely known and in none of the individuals is the significant occipital and periotic region preserved. The upper contour of the skull is slightly arched in the antero-posterior direction, very much as in Loncheres. Seen from above, the general appearance of the skull has considerable resemblance to that of the recent genera, Echimys and 406 PATAGONIAN EXPEDITIONS : PALEONTOLOGY. Loncheres, but is more elongate, with narrower and less tapering cranium and somewhat broader rostrum than in the latter. There is no sagittal crest, but on the hinder half of the parietals is a short, narrow and ob- scurely marked sagittal area, which in front suddenly expands to the full width of the cranium, its borders becoming confluent with the supraorbital ridges. The coronal suture is not so straight as in the modern genera, but is slightly curved, with concavity forward. The supraorbital border is quite as prominent as in the recent genera and has a well defined post- orbital process not present in the latter. The frontals are nearly flat, except anteriorly, when they show a pair of inconspicuous swellings pro- duced by the sinuses. The nasals are relatively quite large and of some- what foliate shape, broadening and becoming very convex anteriorly, where they are curved down on the sides of the rostrum ; posteriorly, they notch the frontals more deeply than in the modern genera. The premaxillaries are much as in Loncheres and the anterior border, in front of the incisor alveoli, forms a similar sharp vertical keel, but the incisive foramina are considerably larger and the ascending rami, which extend to the frontals, are broader. The posterior nares and hard palate resemble those of Echimys, but the palate is rather more triangular, owing to the slight anterior convergence of the two dental series. The mandible differs from that of Echimys and Loncheres in a number of particulars. The ascending ramus is set farther back, so that n% is but partly concealed when the jaw is viewed from the side, while in the recent genera this tooth is entirely hidden ; the coronoid process, though small, is much less reduced than in the two recent genera, and the sigmoid notch is correspondingly deeper ; the masseteric crest, which pursues a similar course, is less prominent and does not extend so far forward ; the ante- rior part of the horizontal ramus is less inclined ventrally. Specimens of Stic homy s are not at all uncommon and the genus is rep- resented in the Santa Cruz beds by a considerable number of species, which differ markedly in size. However, as these species have all been established upon jaws, better material may well modify the results. STICHOMYS REGULARIS Ameghino. (Plate LXV, Figs. 17-19.) Stichomys regularis Amegh. ; Enumeracion sistem., etc. ; 1887, p. 10. The typical species is of moderate size and has a narrow, tapering GLIRES OF THE SANTA CRUZ BEDS. 407 rostrum, the incisors are narrow and appear to be even more so than they actually are, because of the strong convexity of their anterior faces. MEASUREMENTS. No. 9,512. No. 15,555. Amegh, Col. Upper dentition, length ................ 029 .028 " " " pA-mi .......... 013 .013 " " " mi-mi ......... oio .010 Upper incisor, width .................. 002 .002 " " thickness ............... 0025 .0025 Lower dentition, length .............. .022 " pj-mj ........ .013 " " " mT-ms ........ .0095 STICHOMYS REGIUS Ameghino. (Plate LXV, Figs. 16, 20, 20°.) Stichomys regius Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 70. This species is distinguished from the preceding one by its somewhat larger size and more robust proportions and by the broader rostrum and heavier incisors. So far as the available material goes, these differences appear to be quite constant, though it is quite possible that more numerous specimens might show them to be merely individual variations. The fol- lowing measurements of the upper teeth are taken from a specimen in the collection of the American Museum of Natural History (No. 9,495) and those of the lower teeth from a mandible in the Princeton Museum (No. MEASUREMENTS. Upper dentition, length .............. 033 Upper incisor, thickness ............. 003 " " " pA-mi ........ 0145 Lower dentition, length ............. 026 " " " mi-mi ........ 01 1 " " " Pj-mj ....... 015 Upper incisor, width ................ 0025 " " " m-j— m^ ....... 0115 STICHOMYS ARENARUS Ameghino. Stichomys arenarns Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 70. In this species, which is as yet known only from a single mandible, the series of grinding teeth has the same length as in S. regularis, but the horizontal ramus of the jaw is so much more slender as to give it quite a different appearance from that of the typical species. 408 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. STICHOMYS PLANUS Ameghino. Stichomys planus Amegh.; Rev. Argent, de Hist. Nat; T. I, 1891, p. 299. This species differs from all the other known members of the genus in having incisors with plane faces, as in Adelphomys, but differing from the latter in proportions, which are those of Stichomys, the thickness exceed- ing the width. Ameghino has named three other species of Stichomys, founded upon differences of size. ,1 have seen no examples of these species. STICHOMYS CONSTANS Ameghino. Stichomys constans Amegh. ; Enumeracion sistem., etc.; 1887, p. 10. Stichomys gracilis Amegh.; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 300. " The lower incisor has a width of hardly more than i mm. and the four inferior molars occupy a longitudinal space of 9 mm.; the length of the diastema is 3.5 mm. and the height of the horizontal ramus below the first molar [pT] is 5.5 mm." (Amegh., 89', p. 140.) S. gracilis appears to be identical with 5. constans, for, though described as considerably smaller, its dimensions, as given, are almost exactly the same; viz., length p^-m^, 5.8 mm.; depth of jaw below pT, 5.5 mm. STICHOMYS DIMINUTUS Ameghino. Stichomys dimimitus Amegh.; Rev. Argent, de Hist. Nat; T. I, 1891, p. 300. "Size considerably less than that of the preceding species \i. e., S. gracilis], the first two lower molars occupy a longitudinal space of only 3 mm." (Amegh., loc. cit.] ADELPHOMYS Ameghino. Adelphomys Amegh.; Enumeracion sistem., etc., 1887, p. 10. Closely allied to Stichomys and having similar grinding teeth, but dis- tinguished by the incisor teeth which have plane faces and in which the width equals or exceeds the thickness, thus reversing the proportions found in the incisors of Stichomys. ADELPHOMYS CANDIDUS Ameghino. Adelphomys candidus Amegh. ; Enumeracion sistem., etc. ; 1887, p. 10. The typical and somewhat smaller species is distinguished by narrower GLIRES OF THE SANTA CRUZ BEDS. 409 incisors and more slender horizontal ramus of the mandible. The lower grinding series is 14 mm. long and the lower incisor is 2 mm. wide. ADELPHOMYS EXIMIUS Ameghino. Adelphomys eximius Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 69. This is a rather more robust animal than the preceding one, with heavier lower jaw and broader incisors, which measure 2.5 mm. in width. GYRIGNOPHUS Ameghino. . Gyrignophus Amegh. ; Rev. Argent, de Hist. Nat. ; T. I, 1891, p. 300. The original description of this genus reads as follows : "Of characters intermediate between Spaniomys and Stichomys. The first two lower molars \i. e., pT and mij have three folds on the inner side and the last two only two." On making an enlargement of the photograph which I took of the type specimen it appeared that m^ also had three internal folds, the median one of which is much narrower and shallower than the others, and is filled with matrix, so as to be very difficult to see. The tooth has therefore been figured (PI. LXV, fig. 25) with three such folds, though I do not feel entirely confident that such an interpretation is cor- rect. At all events, the pattern of m^ is sufficiently different from that of Spaniomys to justify the generic distinction. (Cf. figs. 23 and 25, PI. LXV.) It is further evident that m^ is only beginning to take on the full complication of the preceding teeth. The only species yet known is GYRIGNOPHUS COMPLICATUS Ameghino. (Plate LXV, Fig. 25.) Gyrignophus complicatus Amegh. ; Rev. Argent, de Hist. Nat. ; T. I, 1891, P- 300. This is a very small animal, about equal to Stichomys constans in size. The series of inferior grinding teeth is 10 mm. in length and the depth of the horizontal ramus below pr is 6 mm. SPANIOMYS Ameghino. (Plate LXV, Figs. 22-24.) Spaniomys Amegh. ; Enumeracion sistem., etc. ; 1887, p. 10. 410 PAT AGONIAN EXPEDITIONS : PALAEONTOLOGY. Closely allied to Stichomys, but with grinding teeth of much more com- plex pattern and comprising species which are of much smaller size than those of Stichomys. Although it is one of the commoner Santa Cruz rodents, this genus is still very incompletely known, and only from jaws and more or less fragmentary skulls, no other part of the skeleton having yet been found. The incisors are very delicate and have convex faces, with thickness slightly exceeding width. The upper grinding teeth have a single internal fold and pA is simpler than the others in having but two external folds, while the molars have three such folds, which are broad and deep and of V-shaped cross-section, thus producing four sharp and prominent external vertical ridges. The molar pattern is thus highly complex and character- istic. Each of the upper dental series is curved, with the convexity of the curvature inward, so that the two rows approximate each other most nearly at about the middle of their course, while the ends are more widely separated. In the mandibular teeth the pattern is reversed, with single external fold ; in pT, mT and -% there are three internal folds, while m¥ has but two, like p-. The resemblance of the upper teeth of Spaniomys to those of the recent Kannabateomys is very close and striking, except that in the latter pA has three external folds, like the molars. On the other hand, the lower teeth of the modern genus, except p-f, are less complicated than those of Spaniomys and are more like those of Stichomys. So far as it is possible to make comparisons, the skull closely resembles that of Stichomys and is also much like that of the recent Echimys, though the upper contour is straighter and the cranium relatively narrower. In one specimen the occiput is retained, though in such a badly fractured condition as to render exceedingly difficult any determination of the sutures in this region. The occiput is like that of Loncheres, though somewhat narrower, while the paroccipital processes are longer and are attached to the largely inflated tympanic bullse. Apparently, the supra- occipital has very small lateral processes, which do not extend downward upon the periotics, but are separated from them by the supramastoid processes of the squamosals. No sagittal crest is present and the short sagittal area is defined on each side by a depression of the cranial roof, producing quite a different appearance from the broadly arched and GLIRES OF THE SANTA CRUZ BEDS. 411 rounded cranium of Loncheres and Echimys. The supraorbital ridges of the frontals are not extended so far backward as in Stichomys and there appears to be no postorbital process ; the forehead is nearly flat, the sinuses causing but slight eminences. The lachrymal is extremely small, as much reduced as in the modern genera named ; the infraorbital foramen has no separate division for the nerve. The rostrum is relatively longer than in Loncheres and its ventral surface is more raised above the level of the hard palate. The interdental portion of the palate is quite short, owing to the extension of the posterior nares, which make a deep, V-shaped incision, with front border almost opposite the middle of m^, thus resembling Echimys rather than Loncheres. The mandibles are all incomplete, lacking the coronoid, condyle and angle ; the masseteric crest is prominent and the fossa is deeper than in Stichomys. In some individuals enough of the ascending ramus is pre- served to show that the coronoid was better developed than in Echimys and Loncheres, and that it was set farther back, hardly concealing m^ ; so far as it is preserved, its ventral border is rounded, not flattened, and the pterygoid cre.st, if present, cannot have been so developed as in the last- named recent genera. As compared with that of Stichomys, the ascend- ing ramus is less erect, more inclined backward. Relationships. — It is evident that this genus is nearly allied to the existing members of the subfamily, but, from the complexity of the denti- tion, it seems unlikely that it was directly ancestral to any of them. Materials are, however, lacking for a definite decision of this latter question. SPANIOMYS RIPARIUS Ameghino. (Plate LXV, Figs. 22, 23.) Spaniomys ripariiis Amegh. ; Enumeracion sistem., etc. ; 1887, p. 10. The typical species is distinguished by somewhat larger size, which is about equal to that of Echimys cayennensis, the length of the lower grind- ing series varying from 10.5 to 13 mm. in length, and in most individuals is about 1 2 mm. The external columns of all these teeth are undivided. In the subjoined table the measurements of the upper teeth and skull are from an American Museum specimen, No. 9,529. MEASUREMENTS. Upper dentition, length 025 Lower incisor, width 0015 " " " pA-mi 012 " " thickness 002 412 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. Upper dentition, length mi-m* 009 Skull, length condyle to premaxillary . .048 Upper incisor, width 0015 Cranium, length to rim of orbit 031 " " thickness 002 Face, length 017 Lower dentition, length 024 Occiput, height on " " " Pf-my 013 Mandible, depth below p^ 008 " " " mT-my oio SPANIOMYS MODESTUS Ameghino. Spaniomys modestus Amegh. ; Enumeracion sistem., etc.; 1887, p. 10. This species, which is much less common than the preceding one, and is known only from mandibles, is distinguished chiefly by its smaller size ; the series of lower grinding teeth measures only 9 mm. in length and the depth of the jaw below pT is only 5.5 mm. ; the anterior portion of the mandible is lower, more slender and relatively more prolonged than in S. riparius. SPANIOMYS BIPLICATUS Ameghino. (Plate LXV, Fig. 24.) Spaniomys biplicatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pat- agonia, 1894, p. 70. A well-marked species, so distinct, indeed, that it may perhaps be referable to a different genus. In size it is slightly smaller than the average individual of S. riparius. The upper teeth are not known ; in the lower teeth the anterior of the two external prisms, into which the crown is divided by the broad and deep median enamel fold, is itself subdivided by a vertical groove into two crests. The type specimen does not make it clear whether this subdivision is present in all of the grinding teeth, or only in my and -3. Length of lower grinding series = 1 1 mm. GRAPH IMYS Ameghino. Graphimys Amegh. ; Rev. Argent, de Hist. Nat; T. 1,1891, p. 300. This genus, though known only from a single fragment of the mandible, appears to be very distinct and carries the complexity of molar pattern in this subfamily to its maximum. Like the other grinding teeth m^, has on the inner side three enamel folds and four crests ; the additional fold is produced by a groove subdividing the median crest, but differs from the other folds and from the corresponding fold of the other teeth in being much shallower and more widely open. GLIRES OF THE SANTA CRUZ BEDS. 413 GRAPHIMYS PROVECTUS Ameghino. (Plate LXV, Fig. 26.) Graphimys provectus Amegh. ; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 300. This is a very small animal, about equalling Spaniomys modestus in size. Length mT— g- = 7 mm. ERETHIZONTID^E. ERETHIZONTIN^E. STEIROMYS Ameghino. (Plate LXVI, Figs. 1-9.) Steiromys Amegh. ; Enumeracion sistem., etc.; 1887, p. 9. It is interesting to note that this genus is more like the recent North American Erethizon than it is like the modern South American genera of the same family. Indeed, it is difficult to frame a generic diagnosis which will satisfactorily separate it from Erethizon, though there are many differences of detail and the number of these differences would doubtless be increased, if more complete material were accessible. The incisors are very heavy, conspicuously more so than in the recent genera, and may either be of equal width and thickness, or the latter di- mension may be slightly greater. In the upper jaw the incisors have feebly convex faces and are very much curved antero-posteriorly, ending in front of p- ; in the mandible the faces are plane, with very narrow and shallow groove near the external border, which is raised and pillar-like ; these teeth are much longer than in the modern genera of the family and extend behind m¥ into the ascending ramus, which gives quite a different appearance to this region of the jaw. The grinding teeth have the same pattern as in Erethizon and Coen- dou, with low crowns, covered with thick enamel, and long roots ; in the masticating surface the valleys are hardly so deep as in the former, but the anterior valley is complicated by a more or less interrupted ridge, which is not present in the recent genera. The two rows of upper teeth are nearly parallel, and though slightly more convergent anteriorly than in Coendou, are much less so than in Erethizon. I have seen no example of the milk-teeth, though it is evident from the comparative degree of \ 414 PAT AGONIAN EXPEDITIONS : PALAEONTOLOGY. abrasion that dp4 long remained in function and was not replaced until after m3 had come into use. Ameghino states that there are two milk- premolars, one of which has no successor (94", 67). The skull (Plate LXVI, figs. 1-6) concerning which some significant points remain to be determined, is, in general appearance, much more like that of Erethizon than that of Coendou, which is principally due to the ab- sence of the inflation of the frontal and nasal regions so characteristic of the latter. A short, but well defined sagittal crest, which is much more prominent than in Erethizon, occupies the posterior half of the parietal zone, passing forward abruptly into a lyrate sagittal area, which is much narrower and has more nearly parallel sides than in the last-named genus. The nasals are longer and more convex transversely thari in the latter, and the dorsal branch of the maxillary zygomatic process is broader, or less antero-posteriorly compressed than in either of the recent genera. The rostrum has about the same relative length as in Erethizon, but is of more uniform width, not narrowing so much ventrally and thus, when viewed from below, is more as in Chcetomys than in either of the other modern genera. The incisive foramina are large, resembling those of Erethizon. None of the specimens shows the shape or limits of the posterior nares. The pterygoids have a wider ventral surface than in the recent genera and do not extend to the tympanic bullse ; apparently the pterygoid fossa is imper- forate, though the skulls are all so damaged here as to leave this somewhat uncertain. The tympanic bullae are far smaller than in Erethizon or Coen- dou, with meatus formed by short, irregular tube, much as in the former. The mandible differs in several respects from that of the recent genera ; the symphysis is shorter and the chin more vertical, and the diastema is relatively much shorter ; the ascending ramus is not set quite so far for- ward and the coronoid is much less reduced, rising above the level of the condyle, while the sigmoid notch is wider and shallower; the masseteric crest is much more prominent and the fossa much deeper and better defined ; the pterygoid crest, on the other hand, is less developed, so that the ventral border of the angle is narrower and less inflected ; the angular process is shorter and the notch between condyle and angle shallower. The alveolus of the incisor forms a broad, shelf-like projection from the inner side of the ascending ramus, rising much higher than in the recent genera and bringing the inferior dental foramen to a much more elevated position, a little below the condyle. GLIRES OF THE SANTA CRUZ BEDS. 415 Of the skeleton, nothing is known but the tibia, fibula, pes, and parts of the ulna and manus of S. d^^pl^catus. The manus (Plate LXVI, fig. 8) is relatively larger than in Erethizon. The lunar, which is not coossified with the scaphoid, is broad and very short proximo-distally, the radial facet extending over nearly the whole dorsal face. The pyramidal is much shorter than Erethizon, hardly more than a flat scale, thinning to an edge on the ulnar side. A distinct central was present, as is shown by the facets of the magnum, which is relatively much smaller than in Erethizon, while the unciform is quite as in the latter; the same is true of the pisi- form, which resembles that of the modern genus, but is relatively shorter and more expanded at the free end. The metacarpals preserved are II, III, IV and V. It is not practicable to determine whether the pollex was developed or rudimentary, for the facet on metacarpal II is not decisive, though, judging from the analogy of the pes, it seems probable that the pollex was functional. The other meta- carpals are remarkably long and slender, especially II, III and IV. Metacarpal II is rather longer than V, shorter than III or IV; the proxi- mal end is oblique to the shaft in both directions, so as to give the bone a somewhat twisted appearance ; the facet for the trapezoid is less concave than in Erethizon and that for the magnum is somewhat smaller than in t the latter ; on the radial side of the head is an articular surface for the trapezium or for I. Metacarpal III is the longest of the series ; it differs from that of Ere- thizon in having a well-defined process which overlaps the head of meta- carpal IV and abuts against the unciform, while in the recent genus there is no dorsal connection with the unciform. The shaft is slender and curved forward ; the hemispherical distal trochlea is prominent, with a well-defined, though shallow, supratrochlear fossa. Metacarpal IV is somewhat shorter and considerably stouter than III, especially toward the distal end, where it becomes irregular. Metacarpal V is much shorter than IV and relatively heavier. The phalanges are very similar to those of Erethizon, but not so long in proportion to the metacarpus. The proximal phalanx is elongate, slender and depressed, with slightly oblique proximal and distal facets ; the second phalanx is also quite long and the ungual forms a long, curved and pointed claw, cleft at the distal end. The tibia, which is separate from the fibula, as in Erethizon, is short 4l6 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. and heavy and shaped very much as in the latter ; the distal end is rather wide, but not much thickened ; the astragalar surface is unequally divided into small internal and very large external facets, with low intercondy- lar ridge, which on the plantar side passes into a long and prominent tongue-like process. The fibula is very slender, relatively more so than in Erethizon, and its distal end is more compressed laterally and expanded antero-posteriorly. The pes (Plate LXVI, fig. 9) is very like that of Erethizon, with longer metatarsals and less reduced hallux ; certain resemblances to Coendo^^, such as the presence of a second tibial sesamoid, are also to be noted. The calcaneum has a short, heavy tuber, with broad and shallow tendinal sulcus on the free end ; the distal, external tuberosity for the attachment of the lateral ligament is a prominent ridge ; the sustentaculum is very prominent and the external astragalar facet is very large and oblique, facing inward more than dorsally ; the cuboid facet is oblique to the long axis of the bone and but slightly concave. The astragalus is short, wide and depressed, with deeply grooved and asymmetrical trochlea, the outer condyle being much the larger ; the neck is very oblique and directed strongly toward the tibial side, ending in a convex, somewhat depressed head : on the plantar side are two large facets for the calcaneum, the exter- nal one of which is continuous with the navicular surface. The navicular is short and narrow, with a shallow concavity for the distal end of the astragalus ; distally, it rests entirely upon the meso- and ectocuneiforms, the entocuneiform having only a lateral contact with it, as is also the case in Coendou and Erethizon. On the tibial side of the navicular is a large, thick and heavy sesamoid, which resembles that of Coendou in shape and connections ; in the figure (LXVI, 9, s] its full size is not shown, because it is partly overlapped and concealed by the second sesamoid (/). The first sesamoid rests upon the navicular and entocuneiform, entirely covering the proximal end of the latter, and on the fibular side it articu- lates extensively with the astragalus, for which it has a concave facet ; on the tibial and dorsal side are two small, subcircular and well-separated facets for the second sesamoid. The latter, which is not present in Ere- thizon, has a somewhat similar shape to that seen in Coendou, but is far smaller and could have had no such functional importance ; it is a flat bone, of subtriangular shape, and is connected only with the first sesamoid by means of two small facets on the inner side of the plantar surface. GLIRES OF THE SANTA CRUZ BEDS. 417 The entocuneiform is a large bone, with principal diameter proximo- distal, but it is also very thick planto-dorsally ; the proximal facet for the first sesamoid is nearly plane and the distal one for the first metatarsal is saddle-shaped, while those for the navicular and second metatarsal are on the fibular side. The mesocuneiform is very small and the ectocuneiform is very large, both having nearly the same shape and proportions as in Erethizon. The cuboid also is very much as in the latter, but has a some- what more oblique facet for the calcaneum and does not come into contact with the astragalus. The metatarsus is remarkably elongate, exceeding the metacarpus in length much more than is the case in Erethizon. Metatarsal I is the shortest of the series, but is stout and well developed ; the proximal end is broad and thick and bears a large, saddle-shaped facet for the entocu- neiform. The shape of this facet and the divergent position of the whole hallux suggest that this digit was opposable, at least to a limited extent. The shaft is broad and antero-posteriorly compressed, and the distal trochlea, which is complete and has a low carina, is asymmetrical, being displaced toward the fibular side. The remaining metatarsals differ little from one another in length, IV being slightly the longest and II and V almost equal ; II, III and IV have slender shafts, of transversely oval section, and arched forward ; the distal trochlea is hemispherical, with a small, but well defined, supratrochlear fossa above it, and a short, low carina on the plantar side. Metatarsal V has an expansion of the proximal end, which ends in a blunt projection from the fibular side, much as in Erethizon, but less heavy and prominent. The phalanges differ from those of the manus only in being longer and heavier, the entire pes much exceeding the manus in all dimensions. Relationships. — No reason is apparent, why we should not regard Steiromys as the actual and direct ancestor of Erethizon, an animal which is demonstrably of South American origin. The Santa Cruz genus is but little more primitive than the recent one and the change from one to the other involves but a slight modification. On the other hand, Steiromys may also be an ancestor of Coendou, as is suggested especially by the presence of the two sesamoids in the tarsus. So long, however, as we remain in complete ignorance of the character of the tail in the fossil, we can hardly decide this question. At all events, Steiromys must be near to the common ancestor of both the North and South American recent 4l8 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. genera. It is interesting to note that the migrant, Erethizon, which is on the outskirts of the distributional area, has undergone less modification than Coendou, which has remained in the original home of the group. STEIROMYS DETENTUS Ameghino. (Plate LXVI, Figs. 6-7".) Steiromys detent^ts Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. This species is distinguished, not only by its smaller size, which is very constant in many specimens, but also by the symmetrical shape of m¥, which is smaller than mT or ^. In the table, the measurements of the upper teeth and skull are from a specimen (No. 9,555) belonging to the American Museum, those of the lower teeth and mandible from No. 15,- 094 in the Princeton collection. MEASUREMENTS. Upper dentition, length 044 Rostrum, width at anterior end 016 Upper dentition, length p4— m^ OI9S Lower dentition, length p-j— m-j- 021 Upper dentition, length ml-m& 014 Lower dentition, length m— m^ 015 Upper incisor, width 004 Lower incisor width 004 " " thickness 004 " " thickness 004 Skull, estimated length 085 Mandible, depth below p? 014 STEIROMYS INTERMEDIUS sp. nov. (Plate LXVI, Figs. 3-4°.) In size this species is intermediate between S. detentus and S. duplicatus, though it cannot be called transitional, because of the constancy of those two species in regard to size. However, size is not the only distinguish- ing character ; the incisors are actually as large as in S. duplicatus and are therefore relatively much larger ; in addition to the external raised border or pillar, is a similar, though much less distinct, pillar on the mesial border ; between the two the anterior face is depressed and flat. The grinding teeth are rather small in proportion to the size of the jaw ; nij is reduced in size and asymmetrical, the posterior lobe of the tooth being much smaller than the anterior lobe. The type of the species is a mandible, No. 15,367, in the Princeton Museum, and it is probable that the upper teeth from the Ameghino col- lection, shown at Plate LXVI, fig. 3, should also be referred to the same species. GLIRES OF THE SANTA CRUZ BEDS. 419 MEASUREMENTS. Lower dentition, length pj-my 025 " " " m-r-mj- .018 Lower incisor, width 006 Lower incisor, thickness 0063 Mandible, depth below my 017 STEIROMYS DUPLICATUS Ameghino. (Plate LXVI, Figs. 1-2", 4, 5, 8, 9.) Steiromys duplicatus Amegh. ; Enumeration sistem., etc. ; 1887, p. 10. This is a large rodent, much exceeding Rrethizon dorsatum in size Whether the manus and pes (PI. LXVI, figs. 8, 9), are properly referable to this species, is not certain, because no teeth were found associated with them, but they very probably are so referable, because, large as they appear, they are but little larger, in proportion to the size of the skull, than in the recent species. The incisors are larger and heavier than in the latter, but the grinding teeth are relatively smaller and the diastema actually shorter ; the raised external border of the lower incisor is distinct, but there is no enamel ridge along the mesial border. A series of com- parative measurements shows many differences of proportion from the Canada porcupine, which is therefore included in the tables. In the first table the individuals marked A. i and A.2 are in the Ameghino collection. MEASUREMENTS. No. E. dor- A.I. A.2. 15,868. salum. Upper dentition, length 060 .054 " " " p4 m8 027 .0245 " " mi-mi 0185 .018 Upper incisor, width 0065 .0035 " " thickness 007 .0045 Lower dentition, length .049 .048 " P*-m5 .0295 .027 " mT-m^ .021 .0195 Lower incisor, width .006 .003 " " thickness .007 .005 Skull, length .120 .089 No. E. dor- 15,156. satum. Tibia, distal width O2O .012 " " thickness 016 .013 42O PATAGONIAN EXPEDITIONS I PALEONTOLOGY. No. E. dor- fS,fS^- satutn. Fibula, distal width 0085 .008 " thickness on .008 Metacarpal II, length 023 .014 " proximal width 006 .004 " distal width 005 5 .004 Metacarpal III, length 027 .016 " " proximal width 006 .004 " " distal " 0055 .004 Metacarpal IV, length 025 .016 " " proximal width 006 .0045 Metacarpal V, length 022 .014 " " proximal width 0055 .005 Manus, digit III, phalanx i, length 014 .01 1 " " " " 2, " 012 .0085 " " " " 3, " 016 .015 Manus, digit III, length 066 .049 " IV, " 064 .048 Astragalus, length 023 .016 " width of trochlea 014 .014 Calcaneum, length .033 .024 Metatarsal I, length 024 .01 1 " " proximal width 009 .006 " " distal width 006 .005 Metatarsal II, length 034 .016 " proximal width .005 5 .004 " " distal width 007 .004 Metatarsal III, length 036 .018 " " proximal width 006 .005 Metatarsal IV, length 038 .020 " " proximal width 0065 .005 Metatarsal V, length 035 .022 " proximal width oio .009 Pes, digit I, phalanx i, length 016 .010 " " " " 2, " ?.oi6 .011 " H, " i, " 018 .012 " 2, " 014 .009 " " HI, » I, « OI9 .012 " " " " 2, " OI3 .0085 " IV, " i, " 0175 .013 " 2, " OI4 .0085 " " " 3, " 017 .0155 " I, length 052 " " IV, » 075 " " V, " 077 GLIRES OF THE SANTA CRUZ BEDS. 421 ACAREMYIN^. Ameghino has proposed this subfamily to include Acaremys and Sciamys, two of the smallest and most abundant of the Santa Cruz rodents. The propriety of marking the distinction between these genera and the Erethizontincz is evident, but it may well prove to be the case that the group should be raised to family rank, for the resemblance to the other subfamily lies principally in the dentition, while in the skull and skeleton there are significant differences. SCIAMYS Ameghino. (Plates LXVI, Figs. 10-11"; LXVII, 1-3, 5-9.) Sciamys Amegh. ; Enumeracion sistem, etc. ; 1 887, p. 9. Small rodents with low-crowned and rooted grinding teeth, much resembling those of Steiromys in pattern ; the crown is divided into two lobes by opposite enamel folds, and each lobe has a secondary fold, or enamel lake, which disappears relatively early on wear. In both jaws the two series of grinding teeth are nearly parallel, or have a slight anterior divergence. The incisors vary considerably in the different species, but are usually very narrow and delicate ; in the upper jaw, they may have either plane or slightly convex faces, but in the mandible they are always plane, except in S. robustus, in which they are feebly grooved. The lower incisors are very long, extending behind the molars into the ascending rami. The skull and skeleton are still very incompletely known, but some significant facts have been ascertained. In its general appearance and proportions the skull is much like that of the recent Echimys, though with much less curved upper contour. In the only specimen that I have seen which retains the posterior portion of the cranial roof (PI. LXVII, fig. 9), there is no trace of sagittal crest or area, though the individual was fully adult. The occiput is broad and low, gently convex in the middle, with very large foramen magnum and small, sessile, widely separated condyles ; the paroccipital processes are small and well divided from the bullae. As in this family generally, the supraoccipital has quite long lateral processes, which extend down on each side upon the periotics. The tym- panic bulla is largely inflated, with auditory meatus in the form of a very short tube, less prominent and less complete dorsally than in Erethizon. 422 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. The periotic has a large exposure upon the occipital surface, sending up a tongue-like process between the squamosal and exoccipital, resembling the arrangement seen in Dolichotis rather than that in the Erethizontince. The supramastoid process of the squamosal is quite narrow, and between this process and the periotic is a deep groove, which is even more pro- nounced than in Dolichotis. The frontal zone is elongate and the fore- head flat, without protuberances formed by the sinuses ; the supraorbital ridges are decidedly more prominent than in Erethizon, and very short postorbital processes are present in some species, not in others. The dorsal ramus of the maxillary zygomatic process is broad, less compressed antero-posteriorly than in Erethizon and the lachrymal, though small, is considerably larger than in the latter. The proportions of the rostrum and nasals differ much in the various species. The hard palate is of nearly uniform width between the teeth ; the posterior nares are narrow and V-shaped. Known mandibles are all incomplete, lacking the condyle and angle ; the masseteric crest is even more prominent than in Steiromys and the masseteric fossa deeper ; the pterygoid crest also, as far as it is preserved, is better developed than in the last-named genus. Considerable parts of the skeleton are associated with an individual of S. varians (No. 15,168) and with one of S. latidens (No. 15,944). All the bones are very small, slight and delicate. Compared with Erethizon, the differences are so many and so marked as to indicate a different man- ner of life ; probably these animals were terrestrial rather than arboreal in habits. As a whole, the neck is relatively a little longer than in Erethizon. The atlas has a remarkably large, subcircular neural canal, which propor- tionately far exceeds that in the recent genus, and the transverse processes are thinner and more prominent than in the latter. In the axis the cen- trum is broad and depressed and has a prominent ventral keel, and the the neural canal is very large. The succeeding cervicals are short and broad and all appear to have been without neural spines, a difference from Erethizon, while the transverse processes resemble those of the latter in their rod-like shape and in the very small development of the inferior lamella. The anterior thoracic vertebrae are very small and have very slender spines, which, though incomplete, appear to have been longer than in Erethizon. The sacrum probably consisted of four vertebrae, three of GLIRES OF THE SANTA CRUZ BEDS. 423 which are preserved, and two are in contact with the ilia. An isolated caudal from near the end of the tail is more slender and elongate than the corresponding vertebra of Erethizon and indicates a longer and thin- ner tail than in the latter. The pelvis is slender in all its parts ; the ilium has an elongate, narrow peduncle, expanding into an anterior plate, which is so crushed that its shape is not determinable, and no ilio-pectineal process is observable. So far as it is preserved, the ischium is laterally compressed and somewhat twisted, and has no distinct sciatic notch. The obturator foramen appears to be of a different shape from that of Erethizon, being narrower dorso- ventrally. All the limb bones are very slender and fragile, with large, thin-walled medullary cavity. None of the fore limb bones is complete, but the parts preserved show that they were considerably shorter than those of the hind limb and that the difference was much more marked than in Erethizon. The very small and slender humerus has a pronounced deltoid crest, quite like that of Erethizon, but extending somewhat farther distally ; the internal epicondyle is very prominent and is perforated by a minute fora- men which is not present in the modern genus ; the trochlea is low and has no pronounced protuberance for the head of the radius ; the supra- trochlear fossa is quite deep and at one point is perforated, though the anconeal fossa, which in Erethizon is quite deep, is in Sciamys almost ob- solete ; the supinator ridge is large. The ulna is extremely slender and has a short olecranon, which, how- ever, is relatively less reduced than in Erethizon, and the facet for the internal part of the humeral trochlea is smaller than in the latter ; the shaft is laterally compressed, becoming very thin toward the distal end, and has a distinct sigmoid curvature. The carpus is not known. Of the metacarpus, metacarpals II, III and IV are preserved and these indicate that the manus was probably penta- dactyl. The metacarpals named are not unlike those of Erethizon in shape, but are much shorter and more slender in proportion to the bones of the pes. Metacarpals II and III are of nearly equal length and articu- late on the ulnar side with the magnum and the unciform respectively; IV is considerably shorter. In connection with the latter the phalanges are preserved. Of these the first and second are not especially character- istic, but the ungual is remarkably slender and straight, not very sharply 424 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. pointed and with only a minute cleft at the tip ; the ventral surface is flat and slightly broadened, remotely suggesting the unguals of certain hoofed animals, and the subungual process is only moderately developed ; the claws must have been quite different from those of Erethizon. The hind limb is disproportionately longer than the fore and all its ele- ments are much longer. Relatively to the skull, the femur is somewhat shorter than in Erethizon, but is much longer in comparison with the hu- merus. The head is large, hemispherical, set upon a much constricted neck and presenting almost directly inward ; the great trochanter is low, but thick, enclosing a small, deep digital fossa ; the second trochanter is low, conical and so completely posterior as to be concealed when the bone is seen from the front ; there is no third trochanter. The shaft is slender, straight and nearly cylindrical, in marked contrast to the broad, antero- posteriorly compressed femur of Erethizon, and the rotular groove is nar- rower, deeper and has better defined margins than in the latter ; the con- dyles are small and project little behind the plane of the shaft. The tibia (Plate LXVII, fig. 2) is rather longer than the femur, thus reversing the proportions of Erethizon; it is very slender and has a slight, though distinct, sigmoid curvature ; the cnemial crest varies in develop- ment in the two species of which the tibia is known, being much more prominent in 6". latidens than in S. varians ; the distal end resembles that of Steiromys, with rather more prominent intercondylar ridge and shorter posterior tongue ; the internal malleolus is almost bisected by a deep ten- dinal sulcus. The fibula, the proximal end of which is not known, has an extremely slender, thread-like shaft; the distal third appears to have been closely applied to the tibia, though without ankylosis ; the distal end resembles that of Steiromys rather than that of Erethizon. The pes (Plate LXVII, fig. 3) is not unlike that of Steiromys, though with certain noteworthy differences. The calcaneum has a relatively longer and more slender tuber, the free end of which is hardly grooved, and the external prominence near the distal end, for the attachment of the lateral ligament is much less conspicuous. The astragalus has an even more asymmetrical trochlea, the internal condyle being hardly more than a sharp ridge ; the neck has no such strong inclination toward the tibial side, but is nearly in the proximo-distal axis of the bone. The navicular is even narrower in proportion to its length than that of Steiromys and, GLIRES OF THE SANTA CRUZ BEDS. 425 as in that genus, has distal facets only for the meso- and ectocuneiforms ; the ecto- and entocuneiforms are longer and narrower than in the latter. The shape of the navicular and entocuneiform make it clear that at least one large tibial sesamoid was present. The metatarsus consists of five members. Metatarsal I is extremely slender and is relatively much more reduced than in Steiromys, not being more than half as long as II ; it is, however, provided with a complete distal trochlea and evidently carried phalanges. Metatarsals II, III and IV are very slender and of nearly equal length, though they are so ar- ranged as to make III project farthest distally, while IV is slightly shorter and heavier than the others ; V is shorter than IV and has a well defined projection from the fibular side of the head, as in Erethizon and Steiromys. The phalanges, so far as they are known, resemble those of the manus, except for their greater length and slenderness. Relationships. — It is evident that Sciamys (and no doubt the same is true of the closely allied genus Acaremys} is related to Steiromys and perhaps referable to the same family, yet with such differences as are at least of subfamily rank. No existing genus can be derived from either of the genera of the Acaremyince, which were probably terrestrial animals that, in a measure, took the place of the rats and mice of the northern hemisphere. It is not unlikely that the invasion of the murines, which took place in the great migration from the north at the close of the Mio- cene, may have been the direct or indirect cause of the extinction of these small mouse-like and rat-like porcupines. The species of Sciamys have been distinguished almost entirely in accordance with differences of size, but this is an untrustworthy criterion and needs to be supplemented by other characteristics. SCIAMYS PRINCIPALIS Ameghino. (Plates LXVI, Figs. io-io6; LXVII, 7-7".) Sciamys principals Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. Among the skulls preserved in the various collections, the one which best agrees with the type of this species is characterized by its very narrow and gently tapering rostrum, a feature strikingly different from all the other skulls. As in most of the species of this genus, the incisors are very narrow and slender ; in the mandible they have plane faces, but in the upper jaw they are slightly convex. 426 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. The nasals are long, narrow and of nearly uniform width, contracting slightly in the middle, and anteriorly are strongly convex ; the free ends are rounded and entire, with a deep notch between nasals and premaxil- . laries. The latter are long and narrow, but of relatively large dorso- ventral height ; between the alveolus of the incisor and the nasal is a thin, triangular plate of bone, which is unusually large in this species. The postorbital process of the frontal is but feebly developed. The following dimensions are taken from No. 15,623: MEASUREMENTS. Upper dentition, length .............. 022 Lower incisor, width ................ ooi 5 " " " pi—mi ........ 009 " " thickness ............. 002 Upper incisor, width ................ 0015 Rostrum, length ................... 015 " thickness ............. 0025 " width at base .............. 008 Lower dentition, length ............. 020 " " " anterior end ........ 006 0085 " dorso- ventral height ........ oio SCIAMYS VARIANS Ameghino. (Plate LXVII, Figs. 5-5*, 9.) Sciamys varians Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. This name may be applied to those skulls which approximate or equal the preceding species in size, but differ from it decidedly in the shape of the rostrum, which is broader, especially at the base, and more tapering anteriorly, while the nasals are quite flat; the interorbital region also is wider than in S. principalis and there appears to have been no post- orbital process. The incisors are relatively narrower than in any other species of the genus and in the upper jaw they have quite plane anterior faces, which may or may not be marked by a very faint, hair-like groove. The remains of the skeleton, other than the skull, which may be re- ferred to this species belong to a single individual (No. 15,168) and consist of the cranium, mandible, two caudal vertebrae, parts of the humerus, ulna, femur, the tibia, calcaneum, astragulus, metatarsal III and certain phalanges of the pes. The description of the bones has already been given in connection with the account of the genus, but attention should be called to the relatively great length of metatarsal III, which exceeds that of S. latidens. In the subjoined table the dimensions of the upper teeth and skull are from No. 15,575, the others from No. 15,168. GLIRES OF THE SANTA CRUZ BEDS. 427 MEASUREMENTS. Upper dentition, length 022 Ulna, width at sigmoid notch 0025 " " " pf—m-g 008 Femur, estimated length 036 Upper incisor, width ooi " proximal width 0075 " " thickness 0027 " distal width 006 Lower dentition, length 017 Tibia, length 038 " " " Pj-mj 008 " distal width 003 Lower incisor, width 0012 " " thickness 003 " " thickness 002 Calcaneum, estimated length 009 Rostrum, length 013 Astragalus, length 0055 " width at base on " width of trochlea 003 " " " anterior end 006 Metatarsal III, length 015 " dorso-ventral height oio " " proximal width 002 Humerus, width of distal end 006 " " distal width 002 " " "trochlea 0035 SCIAMYS ROSTRATUS sp. nov. (Plate LXVII, Figs, 6-6".} This species is intermediate in character between S. principalis and S. varians. The upper incisors have slightly convex and faintly grooved faces and are somewhat broader than in S. varians. The rostrum is more slender than in S. varians, less so than in S. principalis. Compared with those of the latter, the nasals are less convex and narrow more pos- teriorly, giving a broader dorsal surface to the ascending rami of the pre- maxillaries. The frontals have no postorbital processes. The type is No. 15,257 of the Princeton collection. MEASUREMENTS. • Upper dentition, length 0225 Rostrum, length 012 " " " pA-m-3. 008 " width at base OIO Upper incisor, width 0015 " " " anterior end 0065 " " thickness 003 " dorso-ventral height 008 5 SCIAMYS TENUISSIMUS Ameghino. Sciamys tenuissimus Amegh.; fenum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 68. This is much the smallest known representative of the genus and may be" easily distinguished by its minute size. So far, it is known only from mandibles, which differ from those of the larger species in the more pos- terior position of the ascending ramus, leaving all the grinding teeth ex- posed in side view ; so much of the masseteric fossa as is preserved, indi- cates that it was relatively small. 428 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. MEASUREMENTS. Lower dentition, length 012 Lower incisor, thickness 0015 " " " pi— mi . . .005 Mandible, depth below pf 004 Lower incisor, width 0005 SCIAMYS LATIDENS Sp. HOV. (Plate LXVII, Figs. 1-3.) The type of the species (Princeton collection, No. 15,944) is the most complete individual of the genus yet obtained. It consists of the skull, lacking the occiput and basis cranii, mandible, five cervical and several thoracic vertebrae, the sacrum and the greater part of the manus, tibia, fibula and pes. Collected by Messrs. Hatcher and Peterson at Killik Aike. In skull and dentition S. latidens stands well apart from the other species of the genus and forms a transition to Acaremys, to which it would be referable, were it not for the character of the lower incisors. The upper incisors are quite broad, in marked contrast to the slender, delicate teeth found in most of the other species of Sciamys, and have distinctly convex faces, as much so as in Acaremys murinus, while the lower incisors are plane and are also broader than in the various preced- ing species, from which they further differ in the presence of a raised enamel border along the outer margin of the front face. The upper pre- molar is somewhat reduced in size, making the difference between this tooth and m1- unusually great, while n% is conspicuously smaller than in the other species. The skull is characterized by the broad and heavy rostrum with nearly parallel sides, and by the wide, nearly plane interorbital region ; the frontals have distinct postorbital processes, a difference from the other species ; the anterior border of the frontals is excavated in a broad, semi- circular notch, to receive the nasals and premaxillae. The nasals, which are rather short, are narrowest posteriorly, broadening gradually forward ; their posterior half is nearly plane, the anterior portion moderately con- vex. The antero-superior angle of the premaxilla, between the incisor alveolus and the nasal, is very small, much smaller than in S. principals. The palate is somewhat broader in front than behind, and the difference is rather more marked than in the other species. The mandible does not exceed that of S. principals in length, but is GLIRES OF THE SANTA CRUZ BEDS. 429 heavier, and the inferior margin of the angle is unusually broad, owing to the development of the masseteric and pterygoid crests. The parts of the skeleton have already been described in the account of the genus. The tibia, which seems to have been of nearly the same length as in S. varians, has a somewhat heavier distal end, while the me- dian metatarsal is notably shorter than in that species. MEASUREMENTS. Upper dentition, length 023 " " " pA-mi 0075 Upper incisor, width 002 " " thickness 003 Skull, interorbital width 045 Rostrum, length 012 " width at base oil width at anterior end 0085 " dorso-ventral height 0085 Lower dentition, length 020 " pT-m3 008 Lower incisor, width 002 " " thickness 003 Diastema, length 008 Mandible, depth below p? 007 Metacarpal II, length 007 " proximal width 0015 " distal width 0017 Metacarpal III, length 075 " " proximal width 002 " " distal width 002 Metacarpal IV, length 0065 Digit IV, length 0165 Digit IV, phalanx i, length 004 a tt tt o ** OO2 " " " 3, " 005 Tibia, distal width 003 5 " " thickness 003 Calcaneum, length 009 Astragalus, length 0055 " width of trochlea 003 Metatarsal I, length 0065 " " proximal width 0013 " " distal width ooi 3 Metatarsal II, length 013 " " proximal width 0015 " " distal width 002 Metatarsal III, length 0125 " " proximal width 002 " " distal width 002 Metatarsal IV, length 012 " " proximal width 0015 " " distal width 002 Metatarsal V, length oio " • " proximal width 0025 " " distal width . .002 SCIAMYS ROBUSTUS Ameghino. Sciamys robtistus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 68. This incompletely known species differs from the others in such a way as to suggest that better material may require its generic separation. In the Princeton collection it is represented only by one specimen (No. 15,824) consisting of the symphysial region of a mandible, with both in- cisors in place, and retaining the alveolus of pT, together with some frag- ments of limb bones. S, robustus is the largest known species of the genus, and the incisors are of somewhat uncommon proportions, the thick- 430 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. ness not exceeding the width so much as usual, and each one is marked by a groove, shallow and inconspicuous and yet quite distinct ; the mesial border is raised into a fine, almost hair-like ridge, while the outer border is a wider and more distinct ridge. MEASUREMENTS. Lower incisor, width 002 Diastema, length 0115 " " thickness 0025 ACAREMYS Ameghino. (Plates LXVI, Figs, u, 11°; LXVII, 4-4", 10-13. Acaremys Amegh. ; Enumeracion sistem., etc.; 1887, p. 9. Closely allied to Sciamys, though not so well known, because it is much less abundantly represented in the collections. The grinding teeth have the same pattern as in Sciamys, but the incisors, both upper and lower, have convex faces and, in most of the species, are quite broad. The skull also resembles that of Sciamys, with a few differences of detail, which appear to be constant. The dorsal branch of the maxillary zygo- matic process is much more slender ; except in A. minutus, which has a process from the jugal, the frontal has a short postorbital process, which projects more abruptly than in those species of Sciamys which have the process. In the parietal zone Acaremys has a distinct sagittal crest, which is not the case in Sciamys. No part of the skeleton other than the skull has yet been found. ACAREMYS MURINUS Ameghino. (Plates LXVI, Figs, 11, n°; LXVII, 4-4*, 12.) Acaremys murimts Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. Acaremys messor Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent; 1889, p. 126. This species may be distinguished by its broad and blunt rostrum, almost without anterior taper. To it I refer a specimen in the American Museum of Natural History ( No. 9,280) which unfortunately, has no mandible associated with it and may possibly belong to Sciamys latidens, which it closely resembles, but the upper incisors are broader and more strongly convex, while the part protruded from the alveolus is much longer and the abraded surface much more gently inclined ; the rostrum has more nearly parallel sides and the anterior end is blunter ; the upper GLIRES OF THE SANTA CRUZ BEDS. 43! contour of the facial region is straighter, the nasals are narrower behind, broadening more anteriorly, where they are even less convex ; the post- orbital process of the frontal projects more abruptly ; the incisive foramina are larger and the posterior nares of a different shape. The specimens described as A. messor are apparently somewhat larger and more robust individuals of the present species. MEASUREMENTS. Upper dentition, length 0245 Rostrum, length 014 " " " pA-m-3 0075 " width at base 012 Upper incisor, width 0025 " " " anterior end 009 " " thickness 0032 " dorso-ventral height 0095 Skull, interorbital width 0105 ACAREMYS KARAIKENSIS Ameghino. Acaremys karaikensis Amegh. ; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 299. Though originally separated from A. murinus on account of its larger size, the transitions in this respect are so complete, that the species cannot be maintained for that reason alone. However, the validity of the species is evident from the character of the incisors, which are narrower than in the preceding species, and from the shape of the rostrum, which is broad at the base and tapers forward rapidly. ACAREMYS MAJOR sp. HOV. , The type specimen (No. 15,366), a skull without mandible and con- siderably distorted by pressure, was collected at Killik Aike by Mr. O. A. Peterson. It is so much larger than any other known representative of the genus that it probably represents a distinct species. Though the skull markedly exceeds that of A. murinus in size, the incisors are actually narrower, while the grinding teeth are notably larger, especially in width, and are of different relative sizes, pA and m1 being nearly equal, while m- and a are considerably larger ; m3- is not at all reduced, as it is in A. murinus. The rostrum is long, narrowing forward somewhat, but quite broad, even anteriorly. MEASUREMENTS. Upper dentition, length 030 Skull, interorbital width 017 " " " pi-m£ 0085 Rostrum, length 020 Upper incisor, width 002 " width at base 014 " " thickness 003 " " " anterior end 0085 Skull, length 057 " dorso-ventral height oio 432 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. ACAREMYS MINUTUS Ameghino. (Plate LXVII, Figs. 10-10", 13.) Acaremys minutus Amegh. ; Enumeracion sistem., etc. ; 1887, p. 9. This species is smaller and more delicate in all its proportions than A. murinus and in a number of respects its skull is very characteristic. The incisors are narrow and slender, with strongly convex faces, and the grind- ing teeth are very small ; p- and ma are slightly smaller than m1 and a, but ma is relatively less reduced than in A. murinus. The upper incisors are less strongly curved than in any of the other species of this genus, or Sciamys, so that the alveoli do not extend so near to the dorsal border of the premaxillaries, leaving a wider, thin and plate-like strip between the alveolus and the nasal suture and giving quite a characteristic appearance to the rostrum. The latter is rather slender and tapers anteriorly, though not in any marked degree. The frontals are nearly plane, with prominent supraorbital ridges, but with no definite postorbital processes (Fig. 10, PI. LXVII, is erroneous in this respect). On the other hand, the jugal has a distinct postorbital angulation ; anteriorly the jugal ends in a point, not ascending the zygomatic process of the maxillary, and posteriorly it is continued to the glenoid cavity. As in the other species of this genus, the dorsal branch of the maxillary zygomatic process is quite slender, but its broad side is turned more obliquely forward and less laterally. A peculiarity of A. minutus is the shape of the posterior nares, the front wall of which slopes ventrally and forward, forming a narrow, sharply pointed, V-shaped depression in the palate, which extends almost to m-. MEASUREMENTS. Upper dentition, length 019 Rostrum, length 0125 « pi-mi 007 " width at base 0085 Upper incisor, width 0015 " " " anterior end 006 " thickness 0023 " dorso-ventral height 008 Skull, interorbital width 0085 An isolated mandible has the following dimensions : Lower dentition, length 0165 Lower incisor, width 0015 " " p-m 008 " " thickness 002 GLIRES OF THE SANTA CRUZ BEDS. 433 ACAREMYS MINUTISSIMUS Ameghino. ( Plate LX VII, Figs. 11, 11".) Acaremys minutissimus Amegh. ; Enumeracion sistem., etc.; 1887, p. 9. This is the smallest rodent yet discovered in the Santa Cruz beds, being decidedly smaller than Sciamys tenuissimus, from which it may be dis- tinguished not only by the convex faces of the lower incisors, but also by the form of the mandible, the ascending ramus rising more anteriorly and externally, leaving a wider space between itself and the teeth. A specimen in the Princeton collection is even smaller than the type, in which the lower grinding series measures 5.5 mm. in length and the depth of the jaw below pT is 4 mm. * MEASUREMENTS. Lower dentition, length oio Lower incisor, width 0005 " " " pT-m3 005 " " thickness ooi " " " Pj-m^ 004 Mandible, depth below p^ 0033 ACAREMYS TRICARINATUS Ameghino. Acaremys tricar^nat^ls Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 68. Known only from the type specimen. In all of the preceding species of Acaremys pT is of the same pattern as the molars, but in the present .species it is more complex, having two external enamel folds, instead of only one, thus producing three external crests. Size as in A. murinus. I am not entirely satisfied that this species is not founded upon a young individual of the last-named species with dpT still in use. CHINCHILLIDA1. PERIMYS Ameghino. (Plate LXVIII, Figs. 1-15.) Perimys Amegh. ; Enumeracion sistem, etc. ; 1887, p. 12. Sphiggomys Amegh. ; Ibid. This genus is abundantly represented in the Santa Cruz beds and in- cludes a surprising number of species, which, in size, range from very small animals to the largest rodents yet found in the formation. 434 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. The diagnostic features of the genus are to be found in the dentition, which has a general resemblance to that of the recent Viscaccia (Lago- stomus], but with well marked and characteristic differences. The incisors have plane faces and, in comparison with the size of the animal, they are quite slender and short, the upper ones extending but a little distance into the maxillaries ; the lower incisors are longer and extend along the inner side of the mandible to a distance which differs in the various spe- cies, but never reaching behind the molar series. The grinding teeth are entirely rootless and are composed of obliquely transverse FIG. 40. laminae, much as in Viscaccia, with the difference that the laminae are not in contact, but separated by a valley which, at least in the larger species, is filled with cement; the valleys open outward in the lower teeth and the upper pre- molar, inward in the upper molars. In the lower teeth the laminae are connected on the inner side by a narrow bridge Grinding teeth J of Viscacda chi- °f enamel, and on the outer side in the upper molars, while lensis. Crown in the upper premolar both enamel and dentine are con- view, x \. a. tinued around the inner end of the valley, so that this tooth upper j.jas qujte a different appearance from any of the others. teeth, b. Right _, lower teeth *• ne tnir(i upper molar also differs from all the other grind- ing teeth in having three transverse laminae and two valleys, the posterior lamina being shorter and more pyriform than the others. In both jaws the two series of teeth converge strongly forward. The skull is much like that of Viscaccia in its general proportions and in the shape and connections of its various elements, but there are certain not unimportant differences. The occiput is broad and low, with nearly the same relative height and width as in Viscaccia, but the bones are thicker and the occiput is not plane, but has a marked median convexity, with a prominent vertical ridge ; there is no such median fontanelle as is found in the modern genus ; the foramen magnum is of a more transversely oval shape and the condyles are somewhat larger. In none of the specimens are the paroccipital processes preserved entire, but it is evident that they were much shorter than in Viscaccia, though better developed than in the other recent genera of the family. The supraoccipital has a somewhat broader surface on the dorsal side of the cranium than in Viscaccia and the occipital crest is correspondingly thicker; as in the latter, the bone has long lateral processes, which extend down over the periotics, but are GLIRES OF THE SANTA CRUZ BEDS. 435 widely separated from the mastoid processes. In the large species of Perimys the periotic is exposed on the occipital surface, though less ex- tensively than in Viscaccia, while in some, at least, of the small species, it appears only in a narrow fossa between the exoccipital and squamosal ; on the other hand, it is never visible on the cranial roof, as it so conspic- uously is in Chinchilla and Lagidium. The periotic is also smaller than in any of the three recent genera ; the mastoid process is quite well de- veloped. The tympanic is larger than in Viscaccia and thus the auditory bulla has quite a different appearance, and the meatus is a short tube, which, compared with that of the latter genus, is directed more upward and outward, less backward. The parietals are relatively longer than in Viscaccia and support a more distinct sagittal crest, from which quite prominent temporal ridges diverge. FIG. 41. Skull of Viscaccia chilensis, x f . a. Left side. b. Top. The frontals are broad and have a vaulted, convex surface, due to the large sinuses ; this inflated appearance of the forehead is more marked in the larger species of the genus. The supraorbital ridge is prominent and the postorbital process is much better developed than in Viscaccia and the notch in front of it is correspondingly deeper ; in the modern genus a small, separate bone is placed between the anterior ends of the frontals, but I have not observed this in Perimys. The squamosal has a some- what broader supramastoid process than in Viscaccia, but it is of quite a similar shape ; between the anterior end of this process and the periotic is a narrow, oval foramen, which is larger than in Viscaccia, but far smaller than in Chinchilla or Lagidium. The jugal also is much as in Viscaccia, extending behind to the glenoid cavity, and in front apparently rising to 436 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. a contact with the lachrymal. The dorsal branch of the maxillary zygo- matic process is very broad, making the outer wall of the infraorbital fora- men far wider than in the recent genus. The nasals have much the same foliate shape as in Viscaccia, but in their anterior half these bones are much less convex and have no such inflated appearance; while the free ends are bluntly pointed and not notched, but are separated for a considerable distance from the premaxil- laries. The latter are very similar to those of the recent genus, but the masseteric fossa is shallower and of a different shape ; the ascending rami are long, extending over the maxillaries to a suture with the frontals, the shape of which varies in the different species. The hard palate is of tri- angular shape, narrowing forward ; much of it is formed by the palatines, which have a smooth, dense surface, in marked contrast to the almost lace-like texture of the maxillary palatine processes ; the maxillary portion of the palate is less concave than in Viscaccia and the median ridge is lower, while the ventral surface of the palatine bones is broader. The posterior nares are considerably smaller than in the modern genus and there is no such median spine from the front border. The pterygoid fossae are large and are so perforated as to be in communication with the orbits. The mandible is very much like that of Vjscaccia, with certain signifi- cant differences ; the condyle is narrower and more elongate antero-pos- teriorly; the coronoid, though very small, is much less reduced, rising nearly as high as the condyle, from which it is separated by a far narrower and shallower sigmoid notch. The masseteric fossa is very deep and has quite the same elevated position on the ascending ramus as in the modern genus, but is considerably larger; the masseteric crest, which in the ex- isting genera of the family is almost obsolete, in Perimys is very prom- inent, especially in the dentary region of the jaw, becoming less distinct posteriorly ; the pterygoid crest also is better developed, making the angle more concave on the inner side and giving it a much wider ventral margin. The symphysial region of the jaw is less procumbent and the chin rises more steeply from the ventral border of the horizontal ramus than in the existing genera. Unfortunately, little is known of the skeleton, other than the skull, but enough remains to show that there are certain not unimportant differences from all of the recent genera of the family. The parts to be described are all from the quite small species, P. scalaris and P. puellus. The GLIRES OF THE SANTA CRUZ BEDS. 437 cervical vertebrae are relatively somewhat heavier than in Viscaccia and the axis has a broader spine ; in the trunk the anterior thoracic vertebrae are larger and the lumbars smaller; evidently the back was not so strongly arched as in the recent genus, for there is no such disproportion in the relative length of the fore and hind limbs as characterizes the latter, the fore limbs being longer and heavier and the hind limbs shorter and more slender proportionally. The scapula has a slender neck and a rather broad, triangular blade, which, so far as can be determined, is not unlike that of Viscaccia in shape. The humerus, the proximal end of which has not been found, resembles that of the modern genus, but the deltoid crest is even more prominent and rises more abruptly from the shaft ; the distal end is narrower and the internal epicondyle is less prominent ; there is no epi- condylar foramen, but a large supratrochlear perforation, and the supinator ridge is but feebly developed ; the trochlea, which is rather narrow, has a prominent internal flange for the ulna and three facets for the radius, a median convexity, with slightly concave surfaces on each side of it. The fore-arm bones are slender and elongate, with decided forward curvature. The ulna, no specimen of which with complete olecranon has yet been found, has a prominent coronoid process and anteriorly has only a narrow facet for the humeral trochlea, nearly the whole width of which is occupied by the radius ; the shaft is slender, laterally compressed and, on the outer side, is conspicuously channelled for most of its length, and the distal end is contracted to a narrow, convex facet for the pyramidal. The radius has a broad proximal end, with three facets for those on the humeral trochlea ; the shaft, which proximally is of a transversely oval section, for most of its length is of subtrihedral shape, much as in yiscac- cia ; the distal end is unknown. Of the manus only metacarpal V has been found ; this is very small, though relatively larger than in the recent genus, and is of similar shape, except that the distal end is less expanded. The only known example of the femur has lost the proximal epiphysis and is otherwise damaged, but its length may be determined with sufficient accuracy to show that its proportions were very different from those of the femur of Viscaccia, being relatively much shorter and more slender. The small patella is of nearly uniform width ; proximally it is quite thick, thin- ning nearly to an edge at the distal end ; the surface for the femoral trochlea is decidedly convex transversely, very slightly concave longitudi- 438 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. nally. The tibia also is relatively much shorter and more slender than in yiscaccia, in which the tibia is nearly twice as long as the radius, while in Perimys it is only about one third longer ; the proximal portion is thick, owing to the development of the cnemial crest, but for most of its length, the shft is aslender and subcylindrical. The calcaneum has a short, straight and heavy tuber, with parallel dor- sal and ventral borders, and an elongate distal portion, ending in an ob- lique, concave facet for the cuboid. The trochlea of the astragalus is narrow and deeply grooved and the relatively long neck has but little inclination to the tibial side; the head is rather thick planto-dorsally. The number of digits in the pes is not known, but it was quite certainly not less than four and may have been five. The metatarsals are consid- erably longer than the metacarpals, but they are very slender and evidently the hind foot was shorter and far more slender than in yiscaccia. Relationships. — Imperfect as are the known specimens of Perimys, they suffice to prove the close relationship of the genus to yiscaccia and the propriety of including it in the Chine hillidce. Not improbably it is but little removed from the common ancestor of all the existing genera of that family, for the genus is known from formations older than the Santa Cruz. On the other hand, the Santa Cruz species are without phylogenetic sig- nificance and represent a branch of the family which, though flourishing at that period, soon became extinct and did not persist to the later epochs. The numerous species into which Ameghino has divided Perimys re- quire revision, but the material is still too incomplete for any satisfactory performance of this task. The Princeton and New York collections con- tain several individuals which, though approximating Ameghino's types, do not agree at all closely with them ; it will therefore be necessary either to regard most of the species as variable groups, or else to increase their number very considerably. Disregarding size, the species of Perimys fall naturally into two series, though transitions between them occur, distinguished by the character of p^ ; in one series ps is not very oblique, its postero-internal portion is not very strongly compressed, and the valley opens externally ; in the other series pt has a very oblique position, so that the valley opens an- teriorly rather than laterally, and the postero-internal end is very narrow and compressed. As the mandibular dentition of several species is not known, this distinction cannot be made in a consistent manner. GLIRES OF THE SANTA CRUZ BEDS. 439 PERIMYS ERUTUS Ameghino. (Plate LXVIII, Figs. 5, 13.) Perimys emtus Amegh. ; Enumeracion sistem., etc. ; 1887, p. 12. The typical and most abundant species and of quite small size, though by no means the smallest of the genus. The upper incisors are slender and have moderately convex faces ; the grinding teeth are relatively nar- row and in nv1 the anterior lamina projects so as to form an external pillar, the prominence of which varies considerably ; the other molars have no such pillar. The two dental series converge anteriorly, but less strongly than in certain other species. In the mandible pT is but moder- ately compressed on the inner side and the valley opens almost laterally ; only in m-g is an internal pillar formed by the projection of the posterior lamina beyond the anterior one. The occiput is low and wide, the breadth considerably exceeding the dorso-ventral height ; the periotic seems to be excluded from the occipital surface and to be exposed only in a narrow fossa between the squamosal and exoccipital. The tympanic element of the auditory bulla is very largely inflated and closely appressed to the basioccipital, leaving but a nar- row slit for the foramen lacerum posterius ; the posterior nares are narrow and the palatines are relatively broad. The rostrum is slender and elon- gate, somewhat constricted at the base and slightly enlarged at the max- illo-premaxillary suture. MEASUREMENTS. Upper dentition, length 03 5 Occiput width at base '. 021 " " " p-t-mi 014 Tympanic bulla, antero-posterior diam- Upper incisor, width 002 eter Oil '.' " thickness 0023 Zygomatic arch, length 028 Ml, length (i. e., antero-posterior diam- Palate, length to base of rostrum 015 eter) 003 " width at pA 003 Ml, width (i. e., transverse diameter). . .0035 " " "ml oio M£, length 005 Rostrum, length 017 " width 0033 " width at base 008 Skull, length 059 " " " anterior end 007 Occiput, height 014 PERIMYS PROCERUS Ameghino. (Plate LXVIII, Fig. 7.) Perimys procerus Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent; 1889, p. 172. 44-O PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. To this species I refer an incomplete skull in the collection of the American Museum of Natural History (No. 9,507) which agrees well with the type. In size and appearance this species is very near to the preceding one, but the differences are characteristic and constant. The upper incisors, which have plane and not convex faces, have slightly dif- ferent proportions, the width and thickness being almost exactly equal. The grinding teeth are distinctly wider than in the preceding species, the two upper series have a stronger anterior convergence, and the exter- nal pillar of m- is exceedingly small or absent. The hard palate is wider behind, narrower in front than in P. erutus, but the posterior nares are also wider and the palatines narrower. The rostrum has nearly the same proportions as in the latter species ; the ascending ramus of the pre- maxilla forms a narrow strip on the dorsal side of the rostrum, extending a little behind the nasals ; the latter do not contract posteriorly and their hinder portion is concave, not flat ; the forehead is much less convex and inflated than in the larger species. MEASUREMENTS. Upper dentition, length 03 5 Zygomatic arch, length 03 1 " " " pi-m-S. 015 Palate, length to base of rostrum 013 Upper incisor, width 0023 " width at pi- 0025 " " thickness 0023 " " " m^ 012 Mi, length (i. e. antero-posterior diam- Rostrum, length 013 eter) 003 " width at base 0085 Ml, width (i. e. transverse diameter) . . . .004 " " " anterior end 007 M^, length 0055 " dorso-ventral height 012 " width 004 PERIMYS SCALARIS Ameghino. (Plate LXVIII, Fig. 14.) Perimys scalaris Amegh. ; Rev. Argent, de Hist. Nat. ; T. I, 1891, p. 301. The type is a palate with all the grinding teeth in place ; it represents an animal somewhat smaller than P. erutus, from which it is distinguished by the prominent external pillar on all the upper molars. In the large species of the genus the pillars of both upper and lower teeth are very variable, but in P. scalaris and certain other small species they appear to be quite constant. To the same species I refer a very young animal in the Princeton col- lection (No. 15,063), in which pT has just been erupted and shows no signs GLIRES OF THE SANTA CRUZ BEDS. 441 of wear ; the specimen consists of the greater part of a skeleton, unfortu- nately in a very much damaged condition. The lower incisors, which protrude but little above the alveoli, are narrow and have slightly convex faces, which are faintly grooved. In its unworn state, p^ appears to have two valleys, one of which is the true valley and the other is a deep notch, demarcating the internal pillar, which is very prominent ; all the lower molars likewise have well marked internal pillars, produced by the pro- jection of the posterior lamina. Of the skull, only the tympanic bullae and the mandible are preserved ; the bullae are relatively very large, and the horizontal ramus is long, low and thick, and the much damaged angle ends in a very long process, which extends behind the bulla. Most of the limb-bones have lost their epiphyses, so that it is not practicable to give their dimensions, save in a few instances. A description of these bones, parts of the scapula, ulna, metacarpal III, femur, tibia, calcaneum and astragalus has been given in the account of the genus. In the following table the measurements of the upper teeth are from the type in the Ameghino collection, the others are from No. 15,063. MEASUREMENTS. Upper dentition, length pA-m-S. 012 M^, width 003 Ml, length (i. e., antero-posterior diam- Mandible, depth at p^ 008 eter) 002 " " " notch in front of p^ . .005 Ml, width (i. e., transverse diameter) . .0035 Mandible, thickness at p? 0065 M&, length 004 Scapula, height (approximate) 032 - " width 0035 " width of neck 004 Ulna, width at sigmoid notch 004 Lower dentition, length 025 Metacarpal III, proximal width 0025 P*~m* OI3 Tibia,length 044 Lower incisor, width 002 „ ^^ width Qo6 thickness °°2 « « thickness 005 MT> fcng* °°3 Astragalus, length 008 Wldth °°3 « width of trochlea 005 M^, length 003 PERIMYS PERPINGUIS Ameghino. (Plate LXVIII, Figs, n, 12.) Perimys perpinguis Amegh.; Rev. Argent, de Hist. Nat; T. I, 1891, p. 144. A species of medium size, larger than any of the preceding ones, but much smaller than others ; the type is a fragment of mandible with 442 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. mr~s in place. It is evident from the shape of the empty alveolus that pT was much compressed and very narrow in the inner side, yet the val- ley apparently opened laterally, not anteriorly ; on all of the lower molars the internal pillar is strong. To the same species I refer a palate, with all the grinding teeth in place, in the Princeton collection (No. 15,227), which is from a slightly larger ani- mal than the type. This specimen is remarkable for the large size of pA, which projects externally beyond the line of the molars and gives a de- cided curvature to the outer line of the dental series, a curvature which is more marked than in the larger species ; mi and 1 have antero-external pillars. In the table the dimensions of the upper jaw and teeth are from No. 15,227, the length of the lower grinding series is from the type in the Ameghino collection. MEASUREMENTS. Upper dentition, length pA-m& 0215 M-S, length 0075 PA, length (i. e., antero-posterior diam- " width 005 eter) 005 Palate, width at pA 004 P-*., width (i. e., transverse diameter) . . .0065 " " " m^ 022 Ml, length 004 Lower dentition, length p-^-m-g 020 " width 005 Ameghino has described three large species of Perimys, distinguishing them by the development of the pillars, but, as already mentioned, these pillars are very variable in the large species, and in the same jaw a given tooth on one side may have a prominent pillar and on the other side be without a trace of it. Nevertheless, the three species may be distinguished upon other grounds and are probably valid ; at all events, it would be premature to unite them. PERIMYS ONUSTUS Ameghino. (Plate LXVIII, Figs. 3, 3".) Perimys onustus Amegh. ; Enumeracion sistem., etc.; 1887, p. 12. This name may be applied to the somewhat smaller individuals, in which the incisors are narrow and the mandible relatively slender. The specimen which best agrees with the type is a right mandibular ramus (No. 15,230) especially characterized by its slenderness, which, in turn, is due to the relatively low-crowned teeth. The lower incisor is narrow GLIRES OF THE SANTA CRUZ BEDS. 443 and plane ; posteriorly its alveolus forms a marked protuberance on the inner side of the jaw, extending nearly to mT. On pT, the internal pillar is very faintly marked ; indeed, in this individual, the pillar is well devel- oped only on m¥, though it is fairly distinct on IT% also. The horizontal ramus of the mandible is shallow and slender and the symphysial region is comparatively narrow. In the Ameghino collection is a very fine skull with mandible, which is referred to P. onustus, but the incisors are so much heavier than in the indi- vidual here described that it probably belongs to a different and perhaps undescribed species. MEASUREMENTS. Lower dentition, length 051 P^, width (i. e., transverse diameter). . . .0055 " " pj-1% 025 M7, length 008 Lower incisor, width 0032 " width 006 " " thickness 0033 Mandible, depth at PJ 0115 PI» length (*'. e., antero-posterior diam- " " " notch in front of p^ .0075 eter) 006 PERIMYS IMPACTUS Ameghino. (Plate LXVIII, Figs, i, la, 2, 2a, 9, ga.) Perimys impactus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 72. This species is not only larger than P. onustus, but is also of relatively more robust and massive character. The incisors are considerably heavier than in the latter and have more convex faces ; the upper premolar is large, projecting outside of the other teeth and giving a sigmoid curva- ture to the external line of the dental series ; the upper molars normally have the antero-external pillar. The lower premolar is much contracted on the inner side and an internal pillar seems to be constantly present, but varies much in size ; in one individual (Plate LXVII, fig. ga], for example, it is not observable in the grinding surface, though plainly vis- ible from the inner side ; some individuals have a second pillar near the antero-external border. On the lower molars also the pillar is variable ; it is constantly present in m7 and has not been observed on mT, while on m^ it may be large and conspicuous, small, or entirely absent. The skull (PL LXVIII, figs, i, 10) is very large; it bears considerable resemblance to that of Viscaccia, but is actually much longer and rela- tively narrower. The occiput is higher and not so broad and the periotic 444 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. is less extensively exposed upon the occipital surface, though much more so than in the small species of Perimys. The sagittal crest and temporal ridges are more prominent and the parietals on each side of the crest are more concave than in Viscaccia; the tympanics are more largely inflated and more spheroidal in shape, and are not suturally connected with the pterygoids. The forehead is more convex than in the small species of the genus, owing to the large development of the frontal sinuses, and the postorbital processes are long and prominent. The posterior nares are relatively broad. The mandible differs from that of P. onustus in the much greater depth and thickness of the horizontal ramus and in the greater height of the alveolar border above the edentulous region. In one specimen (No. 15,697, PI. LXVIII, figs. 2, 2") the jaw is unusually thick and massive and the masseteric crest is more prominent than in the other individuals ; to some extent, this great thickness may be abnormal or even pathological. MEASUREMENTS. No. No. No. Type. 15,881. 15,053- 15,697- Upper dentition, length p^-m^ 030 .028 P±, length (z. e., antero-posterior diameter) 007 " width (i. e., transverse diameter) 0095 M&, length 009 " width 006 Lower dentition, length p^-m^ 028 .027 ?-(, length 0055 .007 .008 " width 007 .0065 .0075 Mj, length 0055 .0085 " width 008 .007 Occiput, height .030 " width at base .040 Skull, width in interorbital region .043 Zygomatic arch, length .052 Palate, width at pA .005 " " " ml .018 Mandible, depth at pT .018 .017 " " " notch in front of p^ .on .013 " thickness at p? .013 .0145 PERIMYS AMEGHINOI sp. nov. (Plate LXVIII, Fig. 10.) Perimys zonatus Amegh., in part; Enum. Synopt. des Mamm. Foss. de Patagonie, 1894, p. 72. GLIRES OF THE SANTA CRUZ BEDS. 445 Under the name of P. zonatus Ameghino has, I believe, included two quite distinct species. The type of P. zonatus is remarkable for the ob- liquity of its teeth, while the specimen here considered and upon which the description given under the head of P. impacttis was founded, seems to be very different. The description of P. impactus is as follows: "Size as in P. onustus and P. zonatus ; distinguished by pT, i% and ^, which have an internal perpendicular column behind. In P. onustus this column is found only in p^ and n%; in P. zonatus it is present on all four molars" ("94", 72). P. ameghinoivs a very large species, quite equalling P. impactus in size ; it is characterized by p4, which hardly differs at all in shape from the lower molars, being much less contracted on the inner side than in the preceding species, and the valley opens more directly outward, less anteriorly. In the only known specimen all four of the lower grinding teeth have the internal column, but this may not be a constant character. MEASUREMENTS. Lower dentition, length pj-m^ 027 P^, width (i. e., transverse diameter) . . . .007 P?) length (i. e., antero-posterior M^, length 009 diameter) 007 " width 006 In the second section of the genus, corresponding to Sphiggomys, the lower premolar is so turned as to have its major diameter almost coincident with the long axis of the jaw, the valley opening nearly or quite directly forward. Though the two groups of species are fairly well distinguished by this character, transitions between them do occur. PERIMYS PUELLUS Ameghino. (Plate LXVIII, Fig. 4.) Sphiggomys puellus Amegh. ; Rev. Argent, de Hist. Nat. ; T. I, 1891, p. 143- Perimys puelhis Amegh. ; fenum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 72. In the Princeton collection this species is represented by a fairly com- plete skull, with mandible, associated with several cervical vertebrae and bones, more or less complete, of the fore leg and foot. In size, this species does not greatly exceed P. erutus, but it differs considerably from the latter in its proportions. The upper incisors are not known ; those of the lower jaw are rather broad and have perfectly 446 PATAGONIAN EXPEDITIONS : PALEONTOLOGY. plane faces, which are not grooved and but faintly striate. The upper premolar is quite large and its valley is rather more distinctly angulate than usual. The first and second upper molars have prominent external pillars, formed by the projection of the anterior lamina ; in ma this pillar is very small and, on the right side, hardly noticeable. The lower pre- molar is not rotated quite so completely as in the type specimen and the valley does not open quite so directly forward, but the difference is not a marked one. The variability of the internal pillar of the lower grinding teeth is well illustrated by this individual ; on the right side of the jaw pT has this pillar distinctly, though not conspicuously, marked, while on the left side there is no trace of it ; mr has no pillar on either side, while on both sides m^ has a small and n% a large one. Except in size, the skull differs little from that of P. erutus; as in that species, the periotic is not exposed upon the occipital surface, but in a deep and narrow fossa between the squamosal and exoccipital ; the occiput is considerably higher than in P. ertitus, though the difference is, to some extent, due to the crushing which this specimen of P. puellus has under- gone. On account of this crushing it is difficult to determine the length of the sagittal crest (which appears to be relatively longer than in P. impacttis] and the degree of convexity of the forehead. One peculiarity is, however, quite distinct ; namely, that the notch of the supraorbital bor- der, in front of the postorbital process, is much better defined than in any other species in which this region of the skull is known. The foramen which lies above and in front of the auditory meatus, between the periotic and squamosal, is considerably larger and more conspicuous than in P. erutus. The tympanic bulla is very large, larger than in any other species with which I have been able to compare it. The mandible has a high, but thin and laterally compressed, horizontal ramus, on the inner side of which the incisor alveolus forms a hardly noticeable protuberance, much less prominent than in the larger species of the genus. A characteristic feature of this mandible is the abrupt form of the notch in front of p¥ ; forward of this notch the edentulous border rises to the level of the alveolar border, instead of sloping gently to the edge of the incisive alveoli (cf. fig. 4 with figs. 3 and 9, PI. LXVIII). The masseteric crest is proportionately better developed and extends far- ther forward than in the larger species, and the pterygoid crest is also more prominent, making the ventral border of the angle wider and the GLIRES OF THE SANTA CRUZ BEDS. 447 inner side of the ramus more concave. The condyle resembles that of Viscaccia, except in being narrower, and the coronoid rises more nearly to the level of the condyle, though, owing to the shallowness of the sigmoid notch, its freely projecting portion is much shorter. The cervical vertebrae indicate a longer neck, proportionately to the size of the head, than in Viscaccia. The atlas, which is broad and low, has a prominent hypapophysis, which is not present in the modern genus. The axis is broad in front, very narrow behind, with posterior face which is dorso-ventrally concave ; so much of the broken neural spine as remains resembles that of the recent genus, except that it is less inclined back- ward. The other cervicals have oblique faces and the posterior face, as in the axis, is dorso-ventrally concave ; on the third, fourth and fifth verte- brae, at least, the spine is obsolete. It will be unnecessary to repeat here the description of the limb bones given in the accouut of the genus. Upper dentition, length p4— m-S. P-i, length (t. e., antero-posterior diam- eter) P-*-, width (i. e., transverse diameter) . . Mi, length " width Lower dentition, length MEASUREMENTS. .017 PT, length " width Mg-, length " width Occiput, height " width at base Tympanic bulla, length Zygomatic arch, length Mandible, length from condyle . . . " depth at p^ " thickness at p^ " height of condyle " " " coronoid Axis, length, including odontoid. Axis, length excluding odontoid 009 " width of anterior face on .003 5 Third cervical, length of centrum 007 .005 Fourth " " " " 006 .006 Fifth " " " " 008 .004 Humerus, width of distal end oil .035 " " " trochlea 008 .018 Ulna, width at sigmoid notch 005 .005 " " " distal end 002 .004 Radius, approximate length 042 .006 " width of proximal end 0063 .004 Metacarpal III, length 013 .020 " proximal width 003 .020 " distal width 003 .014 Patella, length oio .032 " width 005 .047 Calcaneum, length 017 .010 " " of tuber 007 .006 Metatarsal III, proximal width 0035 .020 " " distal width 004 .018 .013 448 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. PERIMYS PUERASTER Ameghino. Sphiggomys ptteraster Amegh. ; Rev. Argent, de Hist. Nat.; T. I, 1891, P- 143- Perimys piieraster Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie ; 1894, p. 72. Though known only from a single fragment of the mandible, containing the broken bases of the incisor and premolar, this is probably a valid species. It is considerably larger than P. puellus, and the mandible, though with very low horizontal ramus, is much more robust than in that species ; below pT it measures 10 mm. in depth and 9 in thickness. PT> which has an antero-posterior diameter of 6 mm. and a transverse width of 3 mm. and is thus narrower and more elongate than in the preceding species, has its valley turned directly forward. PERIMYS /EMULUS Ameghino. (Plate LXVIII, Fig. 8.) Perimys csmulus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 72. This species also is known only from fragments of the mandible, but is clearly distinguished by its large size, which approximates that of P. onustus and P. impactus, from which it differs in the character of pT. This tooth is of the same form as in P. puellus, with the long diameter coinci- dent with the long axis of the jaw and the valley opening directly forward. The lower incisor is relatively broad and its anterior face is depressed and striate ; ir% has an internal pillar, but mr has not. MEASUREMENTS. Lower dentition, length r-nij 036 P^, width (i. e. transverse diameter). . . .004 " " " p^-i% 020 Mj, length 0065 Lower incisor, width 0045 " width 007 Pj, length (i. e. antero-posterior diam- eter) 0085 PERIMYS ZONATUS Ameghino. Sphiggomys zonatus Amegh. ; Enumeracion sistem, etc. ; 1887, p. 12. Perimys zonatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 72. GLIRES OF THE SANTA CRUZ BEDS. 449 Unfortunately, I have seen no example of this remarkable species and therefore merely translate Ameghino's descriptions in somewhat abbreviated form. "Molars formed by two laminae, separated by a groove and united at one end, as in Perimys, but more compressed and the laminae not placed in complete juxtaposition, but obliquely for only one-half or one-third of the width and with perpendicular, enamel-free bands" ('87*, 12). " The lower molars measure 4 mm. in width by 9 mm. in length ; they are implanted more obliquely than in any of the other genera, so much so that they may be said to be placed with their major diameter in almost the same direction as the long axis of the jaw and in such a way that the succeeding molar is placed with its antero-internal border against the postero-external border of the tooth in front of it" ('89*, 170; PI. VII, figs. 23, 24). "Size considerable, larger than Lagostomus trichodactylus. Upper molars of the same type as in Perimys, but implanted much more obliquely to the long axis of the jaw and more compressed antero-posteriorly " ('91*, 143). The following species are represented by such incomplete materials as to permit of no satisfactory determination of their validity. PERIMYS PLANARIS Ameghino. Perimys planaris Amegh. ; Rev. Argent, de Hist. Nat; T. I, 1891, p. 144. Perimys planaris Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 71. Perimys planaris Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 1898, p. 179. PERIMYS ANGULATUS Ameghino. Perimys angulatus Amegh.; Rev. Argent, de Hist. Nat.; T. I, 1891, p. 301. Perimys angulatus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 72. Perimys angulatus Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 1898, p. 179. 450 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. PERIMYS PACIFICUS Ameghino. Perimys pacificus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie ; 1894, p. 72. Perimys pacificus Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 1898, p. 179. PERIMYS REFLEXUS Ameghino. Perimys reflexus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 72. Perimys reflexus Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 1898, p. 179. PERIMYS DIMINUTUS Ameghino. Perimys diminutus Amegh.; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 73. Perimys diminutus Amegh. ; Segundo Censo de la Repub. Argent. ; T. I, 1898, p. 179. PROLAGOSTOMUS Ameghino. (Plate LXVIII, Figs. 15-19.) Prolagostomus Amegh.; Enumeracion sistem., etc.; 1887, p. 11. Lagostomus Amegh. in part ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent.; 1889, p. 185. ? Sphceramys Amegh.; Enumeracion sistem., etc.; 1887, p. 13. f Sphceromys Amegh.; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent; 1889, p. 169. This genus is much less abundant and varied than the preceding one and is even less well known, owing to the scanty and fragmentary nature of the material. The incisors are relatively narrower and more slender than in Viscac- cia and differ from those of Perimys in having decidedly more convex faces; another difference from the latter genus is in the much greater length of the lower incisor, which extends for nearly or quite the whole length of the molar series. The grinding teeth are composed of oblique laminae in close juxtaposition, very much like those of Viscaccia, but apparently without cement between the laminae, which are separated by a single layer of thin enamel, which, however, is but little thinner than that on the periphery of the tooth ; the laminae are demarcated by a vertical GLIRES OF THE SANTA CRUZ BEDS. 451 groove, which in the upper teeth is internal and in the lower teeth exter- nal ; the latter, except usually m^, have masticating surfaces of somewhat pyriform shape, the postero-internal end being narrow and compressed. The last upper molar differs from the others in having a third, posterior lamina, the development of which differs in the various species and is also subject to considerable individual variation. The two rows of upper teeth converge anteriorly though not so strongly as in Perimys. In the lower grinding teeth there is not only a well defined external vertical groove, but the anterior lamina projects outward beyond the posterior one, espe- cially in m?, in which the posterior lamina is very narrow; these teeth have no distinct internal side, the anterior side curving gradually into the posterior without angulation. Though the skull is far from being completely known, it evidently agrees in essentials with that of Perimys and Viscaccia and is rather more like the latter than the former, while in some respects it is intermediate between the two. The occiput is like that of Perimys in shape, in the median convexity and in the absence of any vacuity above the foramen magnum, but the bones are thinner and the periotic is more extensively exposed upon the occipital surface, though less than in JSiscaccia, and the mastoid process is very small. As in the latter genus, there is no fossa between the squamosal and exoccipital, this region being made convex by the protuberance of the periotic, along which runs the continuation of the occipital crest, which is less prominent than in the modern genus. The condyles have the same high and narrow shape as in the latter, but the paroccipital processes, which are broken in all the specimens, were evidently smaller. Like that of Perimys, the tympanic bulla is largely inflated, and the opening into it, below the auditory meatus, is also large ; anteriorly the bulla sends forward a process to connect with the pterygoid. The supramastoid process of the squamosal is relatively wider than in Viscaccia and the sagittal and temporal crests are more prominent, while laterally the parietals are more concave. The rostrum differs much in its proportions in the various species ; the nasals are quite flat anteriorly and do not show the foliate shape seen in Perimys and Viscaccia. At least, this is the case in P. profluens, the only species in which the nasals are known. The premaxillae are shorter and the predental portion of the maxillaries longer than in the recent genus, and the fossa for the preorbital part of the masseter muscle is shallower, 452 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. but has much the same shape. The incisive foramina are larger and the premaxillary spines are broader than in the latter, and, in some species at least, there is an opening in the median line, between the premaxillaries and in advance of the incisive foramina, as is also the case in Perimys and Viscaccia. Nearly the whole of the hard palate is made up of the wedge-like palatines, the maxillaries having practically no palatine pro- cesses ; the median ridge and posterior spine of the palatines are quite as in Viscaccia. In all the examples of the mandible that I have seen the ascending ramus is lacking, and nothing is known of the condyle, coronoid or angle. The horizontal ramus is very much like that of Viscaccia and differs from that of Perimys in the small size of the masseteric crest and fossa, but the symphysial region is somewhat shorter and less procumbent than in the modern genus, the ventral border inclining more steeply upward. The ventral surface in this region has the same finely punctate appearance as in Viscaccia, but the punctate area is extended farther back along the whole length of the incisive alveolus. A few fragments of the hind limb have been found in association with P. divisits; these differ from the corresponding parts of Perimys in their relatively much greater size, in which respect they even surpass those of Viscaccia. The ilium has its principal diameter directed more dorso- ventrally than in the latter; the peduncle is shorter and the anterior expansion greater and more abrupt, and the ilio-pectineal process is decid- edly better developed, while the prominent acetabular border, so far as it is preserved, pursues a somewhat less oblique course ; the iliac surface is quite broad. None of the fore limb bones has yet been found, so that it is not possible to make any direct comparison between the fore and hind limbs. How- ever, as the femur and tibia are far larger in proportion to the size of the head than in Perimys, it may be inferred that the difference in the relative lengths of the fore and hind limbs was at least as great as in Viscaccia. The femur differs in several respects from that of Perimys, in which respects it approximates that of the recent genus. As already mentioned, it is relatively even larger than in the latter, but as Prolagostomus was actually a much smaller animal, the relation may be as well expressed by saying that the head is proportionately smaller in the latter. In propor- tion to its length, the femur is more slender than in Viscaccia; the head GLIRES OF THE SANTA CRUZ BEDS. 453 is small, hemispherical and set upon a slender neck ; the great trochanter has lost its epiphysis in all the specimens, but was evidently very large, and the digital fossa is very deep ; the second trochanter is prominent, but less massive than in the modern genus, and, as in the latter there is no trace of a third trochanter. The shaft is much stouter than in Perimys and has not such a cylindrical shape, but is antero-posteriorly compressed ; a strong linea aspera externa runs down the shaft for a greater or less dis- tance from the great trochanter. The condyles project more prominently behind the plane of the shaft than in Viscaccia and the rotular groove is more symmetrical, the external border being raised as high as the internal. There is no way of determining the length of the tibia from the frag- ments, but it clearly was very much longer and heavier than in Perimys, more slender than in 1/iscaccia and it differs in several respects from the latter; the external condyle has no such hook-like process from its postero-external angle, the cnemial crest is decidedly less prominent and the proximal part of the shaft is more deeply channelled on the posterior side. The distal end is very much as in Viscaccia; the astragalar surface is asymmetrical, with much larger facet for the external than for the internal condyle ; the intercondylar ridge is low, but the posterior, tongue- like process is both long and broad ; the internal malleolus, which is quite prominent, is not grooved by a tendinal sulcus, as it so conspicu- ously is in Perimys. Relationships. — While Prolagostomus is still far too imperfectly known for any definite determination of its phylogenetic significance, yet all that we do know concerning it confirms Ameghino's original suggestion ('87*, 12) that it is the actual and direct ancestor of Viscaccia. On the other hand, it has certain unmistakable likenesses to Perimys, which indi- cate that some early, pre-Santacruzian genus, not very far removed from the latter, was the common ancestor of the family. I have seen no example of the supposed genus Sphceromys, but Ame- ghino's description of it strongly suggests that it was founded upon a young individual of the present genus, with dp- still in place. PROLAGOSTOMUS PUSILLUS Ameghino. (Plate LXVIII, Fig. 17.) Prolagostomus pusillus Amegh. ; Enumeracion sistem., etc.; 1887, p. n. fSph&ramys irruptus Amegh. ; Ibid., p. 13. 454 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. ? Sphceromys irruptus Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent.; 1889, p. 169. This, the smallest known species of the genus, is distinguished not only by its small size, but also by the character of m-, in which the pos- terior prolongation is short, straight, directed backward, not obliquely inward, and there is no groove demarcating the process from the second lamina. The incisors are very narrow, hardly exceeding i mm. in width. In the mandible p¥ and m^ are smaller, mT and ^ somewhat larger. The upper grinding series measures 10 mm. in length, and the lower 9 mm. PROLAGOSTOMUS DIVISUS Ameghino. (Plate LXVIII, Fig. 16.) Prolagostomus divisus Amegh. ; Enumeracion sistem., etc.; 1887, p. 11. This species is considerably larger than the preceding one, from which it farther differs in the larger size of the posterior prolongation of m-, which is set off from the second lamina by a deep groove on the inner side ; the size and direction of this process are subject to much individual variation and may differ notably on the two sides of the same skull, but in all cases it is larger than in P. pusillus and the demarcating groove is never absent. The incisors are narrow and slender, the thickness hardly exceeding the width. In the lower series, pT is considerably and m^ slightly smaller than mT and ¥. The rostrum is strikingly long, narrow and tapering, but with relatively large dorso-ventral diameter ; the palate is short and transversely concave, with very prominent median ridge, and the posterior nares are large. In Ameghino's measurements of this and the following species are dis- crepancies, probably typographical, which make it impossible to use them for purposes of comparison. The two individuals in the Princeton col- lection, from which the following measurements are taken, appear to be somewhat larger than the type specimen. MEASUREMENTS. No. No. 15,570 15,^82 Upper dentition, length 036 " pA-mi 014 Upper incisor, width 002 " " thickness 0023 GLIRES OF THE SANTA CRUZ BEDS. 455 No. No. f5,570 15,882 Lower dentition, length -0325 " Pr-mT .015 Lower incisor, width .0023 " " thickness .0025 Occiput, height 017 " width at base 026 Tympanic bulla, antero-posterior diameter 012 Palate, width at p± 003 5 " "ml 008 Rostrum, length 019 " width at base oio " " " anterior end 007 " dorso-ventral height Oil Mandible, depth at pT .009 " " at notch in front of pT .0065 " thickness at py -0075 Femur, estimated length from head 058 " proximal width 013 " distal width .on " width of shaft in middle 006 .0063 " thickness of shaft in middle 004$ .00$ Tibia, proximal width .012 " " thickness .010 " distal width .008 " " thickness .006 PROLAGOSTOMUS PROFLUENS Ameghino. (Plate LXVIII, Figs. 15-18.) Prolagostomus profliiens Amegh. ; Enumeracion sistem., etc. ; '1887, p. 1 1. The following description is founded upon a specimen in the collection of the American Museum of Natural History (No. 9,588). In size this species is nearly the same as the preceding one, but is decidedly heavier and more robust. The incisors are distinctly stouter and in the upper grinding teeth the anterior lamina projects more prominently on the outer side. The posterior prolongation of m- varies considerably in size, shape and direction, but it is usually larger than in P. divisus and is di- rected more obliquely inward. The rostrum differs notably in appearance from that of the last named species ; its length is not certainly known, but it is much broader and tapers less anteriorly, yet its dorso-ventral height is less. The unpaired opening between the premaxillae and in PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. front of the incisive foramen is either wanting, or else has a more posterior position than in P. divisus. The palate is less concave transversely and the median ridge is less prominent than in the latter, while the posterior nares do not extend so far forward. MEASUREMENTS. Upper dentition, length pA-m& ....... 015 Palate, width at m& ................. 009 Upper incisor, width ................ 0025 Rostrum, width at base ............. 013 " " thickness ............. 0x335 " " '.' anterior end ...... .010 Palate, width at p± ................. 004 " dorso-ventral height ........ 009 PROLAGOSTOMUS IMPERIALIS Ameghino. (Plate LXVIII, Fig. 19.) Prolagostomus imperialis Amegh.; Enumeracion sistem., etc.; 1887, p. 12. This species is known only from mandibles, the best preserved of which is No. 9,587 of the American Museum's collection. It is distinguished not only by being the largest known species of the genus, but also by the slenderness of the incisors, which are actually thinner than in P. pro- fliiens and are therefore relatively much smaller. Another distinction from all the preceding species is the relative size of the grinding teeth, the series of which is proportionately longer, making up more than half of the total distance from the incisor to the last molar, while the sym- physial region is relatively shorter. The premolar is small ; m5 has a much greater antero-posterior length than any of the others, but it is somewhat narrower than MEASUREMENTS. Lower dentition, length .............. 036 Lower incisor, thickness .............. 003 " " " Pj-mj ........ 019 Mandible, depth at pT ............... oil Lower incisor, width ................ 0025 " thickness at p^ ............. 007 PROLAGOSTOMUS OBLIQUIDENS sp. nov. The type of this species is unfortunately a mere fragment of the man- FlG 2 dible, containing the incisor and the premolar, but the latter is so peculiar and characterisistic that the distinctness of the species is open to little Type of Prolagostomus doubt. In size, the present species is about the obliquidens; mandible, crown same as p impenalis, but the premolar is much narrower and is so rotated that its long diam- eter is almost coincident with the axis of the jaw, a character which is GLIRES OF THE SANTA CRUZ BEDS. 457 found in no other species of the genus, but occurs in several species of Perimys ; the external groove between the laminae, which is unusually deep, thus becomes anterior. The lower incisor is of almost exactly equal width and thickness and is therefore thinner than in P. imperialis. The type specimen was collected by Mr. Hatcher at Killik Aike. MEASUREMENTS. Length r-p^, inclusive 022 P?, length (i. e., antero-posterior diam- Lower incisor, width 0025 eter) 004 " " thickness 0025 PT, width (i. e., transverse diameter) ... .002 PROLAGOSTOMUS AMPLUS Ameghino. Prolagostomus amplus Amegh. ; Hnum. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 73. Of this species, only the type specimen, a mandibular ramus, is known, but it appears, nevertheless, to be a valid one. The lower grinding series, which measures 12.5 mm. in length, is given a different appearance from that of any of the preceding species by having all the teeth of nearly the same size. Ameghino has named two additional species of Prolagostomus, concern- ing which I am not able to add anything to his account. PROLAGOSTOMUS LATERALIS Ameghino. Lagostomus lateralis Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent; 1889, p. 185. Prolagostomus lateralis Amegh. ; 6num. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 73. Prolagostomus lateralis Amegh. ; Seg. Censo de la Repiib. Argent. ; T. I, 1898, p. 179. PROLAGOSTOMUS PRIMIGENIUS Ameghino. Lagostoimts primigenius Amegh. ; Contrib. al. Conoc. de los Mam. Fos. de la Repub. Argent. ; 1889, p. 186. Prolagostomus primigenius Amegh. ; foium. Synopt. des Mamm. Foss. de Patagonie; 1894, p. 73. Prolagostomus primigenius Amegh. ; Seg. Censo de la Repub. Argent. ; T. I, 1898, p. 179. 458 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. PLIOLAGOSTOMUS Ameghino. Pliolagostomus Amegh. ; Enumeracion sistem., etc.; 1887, p. 12. This very rare and imperfectly known genus is closely allied to the pre- ceding one, but differs from it: (i) in the shortness of the lower incisor, which reaches only to pT, instead of extending the whole length of the grinding series, and therefore the protuberance along the inner side of the mandible, so conspicuous in Viscaccia and Prolagostomus, is wanting; (2) in the form of the grinding teeth, which are much less oblique to the axis of the jaw and which, at least m^ and ¥, have as great an antero-pos- terior diameter internally as externally ; the same teeth have a definite inner side, which forms an angle with the anterior side, not curving into it gradually. Furthermore, in some of the teeth, notably mT, there is an internal groove between the laminae, not so deep as the outer groove, but quite distinct. In the Ameghino collection are some upper molars referred to this genus, which differ from those of the mandible in being of more oval shape, while the posterior prolongation of m-, or incipient third lamina, is directed transversely, not backward, or obliquely inward, as it is in the preceding genus. The mandible resembles that of Prolagostomus in shape and in the small size of the masseteric crest and fossa. Too little is known of Pliolagostomus for any definite determination of its phylogenetic significance, but it appears to be merely an aberrant member of the family, which has left no descendants. PLIOLAGOSTOMUS NOTATUS Ameghino. (Plate LXVIII, Fig. 20.) Pliolagostomus notatus Amegh. ; Enumeracion sistem., etc.; 1887, p. 12. This is a very small animal, exceeding Prolagostomus pusillus but little in size. In the type specimen p-4- and r% are considerably smaller than mT and ^. In the Princeton collection is a mandible (No. 15,087) of a very young animal, in which pT, though erupted, had not yet come into use, which differs from the type in several respects and, though of similar size, may possibly represent a different species ; p^ is very small, but rr% is larger than mT, and the mandible is deeper anteriorly. GLIRES OF THE SANTA CRUZ BEDS. 459 MEASUREMENTS. No. Type. 1^,087. Lower dentition, length 019 " " " Pj-niy on .on Mandible, depth below p^ 005 .0065 " my 008 .008 SCOT^UMYS Ameghino- Scotcewnys Amegh. ; Enumeracion sistem., etc.; 1887, p. 12. It is most unfortunate that this highly interesting genus should be so rare as to be known only from a few teeth. The upper molars are com- posed of two laminae, separated internally by a deep enamel fold or valley, the breadth of which diminishes much with abrasion. In addition to the two principal laminae, there is an incipient third one, in the form of a process from the outer end of the second lamina. Each tooth thus has much the appearance of m- in Prolagostomzts pusillus, except that the posterior process is rather shorter. Of the lower teeth only pT is known and in this the incipient third lamina is anterior. Ameghino's suggestion ('89*, 188), that genus is the forerunner of Chinchilla and Lagidium is probably correct, but the material is far too scanty for any satisfactory determination of this question. SCOT/EUMYS IMMINUTUS Ameghino. (Plate LXVIII, Fig. 22.) Scotceumys imminutus Amegh.; Enumeracion sistem., etc., 1887, p. 12. The single known species is very small, the length from pA to ma, in- clusive, being 6 mm. ; the upper teeth are obliquely implanted and the two dental series converge anteriorly, the palate measuring 2.5 mm. in width at pA and 5 mm. at ma. SPHODROMYS Ameghino. Sphodromys Amegh. ; Enumeracion sistem., etc. ; 1887, p. 13. Of this remarkable genus I have seen only two specimens in the Ameghino collection, neither of which is the type ; both are fragments of mandibles, one containing pT and the other dpT. According to Ameghino (89*, 170), the lower molars are much like those of Perimys, but the pre- molar is entirely different from that of any other known member of the 460 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. family ; in the abraded state it has one deep external and two much shal- lower internal enamel folds, which divide the tooth into two principal lobes, in the anterior one of which is a minute enamel lake. The milk premolar is much more complex. The incisor is short and extends only to the premolar. The masseteric crest is very prominent. SPHODROMYS SCALARIS Ameghino. (Plate LXVIII, Fig. 21.) Sphodromys scalaris Amegh. ; Enumeration sistem., etc.; 1887, p. 13. The extremely small size of the animal is the only specific character that presents itself. Length from pT to r%, inclusive, 7 mm. CAYIID&. (Eocardidce Amegh.) EOCARDIA Ameghino. (Plates LXVIII, Figs. 23-25; LXIX, i-io, 17; LXXI. Eocardia Amegh. ; Observ. gen. sobre el Orden de los Toxodontes, etc. ; La Plata, 1887, p. 65. Dicardia Amegh. (subgenus) ; Revist. Argent, de Hist. Nat. ; T. I, 1891, p. 302. Dicardia Amegh. (genus) ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 74. Tricardia Amegh. (subgenus) ; Revist. Argent, de Hist. Nat. ; T. I, 1891, p. 302. Tricardia Amegh. (genus) ; Enum. Synopt. des Mamm. Foss. de Pata- gonie; 1894, p. 74. Hedymys Amegh. ; Enumeracion sistem., etc.; 1887, p. 14. Hedimys Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 1894, p. 74. This is one of the most abundant and characteristic of Santa Cruz rodents, of which nearly the entire skeleton is represented in the Prince- ton collection, so that it is possible to make satisfactory comparisons with other contemporary and with recent genera. The dentition closely resembles that of Dolichotis, though in several respects that of the Santa Cruz genus is much more primitive. The in- GLIRES OF THE SANTA CRUZ BEDS. 461 cisors are quite narrow and slender and have convex faces ; they are of no great length, the lower one extending only to the line of m5. The grinding teeth are prismatic and rootless. The upper premolar is not molariform, as it is in Dolichotis, but is simpler than the molars, consist- ing of a single, subtriangular column, with a well-marked groove upon the anterior face. There is much variation, sometimes even in the same individual, in the size of this tooth and in the depth of the groove. The FIG. 43. Grinding teeth of Caviidae. a. Right upper teeth, a' right lower teeth of Dolichotis magel- lanica, x \. b. Right upper teeth, b' right lower teeth of Cavia cobaya, x f . first and second upper molars are each composed of two triangular prisms, with apices directed inward and joined externally at the bases ; the faces of the prisms are slightly convex, giving them a heart-like shape on the masticating surface ; more or less cement is deposited in the valley be- tween the prisms, at least in some of the species, otherwise these teeth are quite as in Dolichotis. The third molar has a postero-external prolonga- tion, which differs somewhat in size and shape in the various species, but is always smaller than in the recent genus. In the crowns of the unworn teeth (see PI. LXVIII, fig. 27) may be observed three broad and shallow valleys, which invade the crown from the outer side, one in each prism and one in the space between the prisms, which space is much broader than at a subsequent stage. Very early these valleys become separated from the outer wall of the tooth and con- verted into enamel lakes and, by the time that the animal is fully adult, even the lakes have been entirely worn away (cf. figs. 236 and 27, PI. LXVIII), while the permanent internal valley is so extended outward that the prisms are connected only by a very narrow neck of enamel and dentine. All the upper grinding teeth are so curved as to present the grinding surfaces somewhat externally, but the curvature is not so strong 462 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. as in the recent Cavia and Dolichotis, and the anterior convergence of the two upper dental series is much less than in them. The fore-and-aft plane of the grinding surfaces is nearly horizontal, without the inclination downward and forward which is so conspicuous in Dolichotis. The lower premolar is subject to much individual variation, as well as to considerable specific differences ; I have observed several instances in which notable differences may be seen in the form of this tooth on the two sides of the same jaw. The crown is molariform and consists of two prisms, the anterior one of which is usually smaller than the posterior and may be of either elliptical or triangular cross section, while its anterior face may or may not have a vertical groove. When present, this groove varies greatly in depth, even in the same individual and in some species it becomes so deep as to divide the anterior prism into two, but every stage of the transition to this extreme may be observed. The lower molars consist each of two triangular prisms, with the valley between them opening outward, and the teeth are curved, so as to present the grinding surfaces somewhat inward and thus oppose those of the upper teeth. The unworn lower teeth have internal shallow valleys, corresponding in num- ber and position to the external valleys of the upper teeth. In both upper FIG. 44. Eocardia sp., teeth of young individuals, lower right side, external and crown views, x f . a. Dp¥ in very young stage, b. Dp?, mT and j, later stage, A. M. N. H. and lower molars the narrow edges of the prisms are usually set off by exceedingly fine grooves to form obscure pillars ; this feature is, however, extremely variable. The milk premolars, which remain in function until after the eruption of the last molar, differ from all of the permanent teeth in having roots. Otherwise, dp- has the pattern of the molars (PI. LXVIII, fig. 27) and is composed of two prisms, separated by a deep internal valley, with three enamel folds from the outer side of the crown, which soon become isolated GLIRES OF THE SANTA CRUZ BEDS. 463 as lakes. In the mandible, dpT is more complex than the molars (PI. LXIX, fig. 17); in addition to the principal internal valley there is a second one, anterior to the former and of less vertical extent ; by the time that the tooth is ready to be shed, this anterior internal valley is a mere notch in the inner wall of the crown and may have disappeared altogether. The three shallow external folds correspond in shape and position to those of the molars, but have been worn away before the tooth is replaced. Skull. — So far as I am aware, no entirely complete skull of this genus has yet been found, but, by combining the various specimens, it is possible to ascertain almost all the significant facts of structure. The skull has re- semblances to those of both Dolichotis and Cama; it is narrower and more slender than the former, especially in the cranial and interorbital regions and the upper contour is straighten (The strongly arched appearance seen in the specimen figured in PI. LXVIII, fig. 23, is chiefly due to crushing, which has much depressed the parietal region. To a certain extent, the occiput is intermediate in character between that of Dolichotis and that of Cavia, being lower and wider than in the former, higher and narrower than in the latter; the foramen magnum is relatively smaller and the median vertical crest less prominent than in either of the recent genera, while the paroccipital processes are shorter. As in Dolichotis, the periotic does not appear upon the occipital surface, and apparently there is no mastoid process. None of the specimens dis- plays clearly the limits of the periotic, but in the nearly allied genus Schistomys this bone has much the same shape and connections as in Dolichotis. The tympanic bulla is of only moderate size, and is relatively less inflated than in the last-named genus, but with quite similar short and incomplete tubular meatus. The parietal region is more or less injured in all the specimens : so far as they are preserved, the parietals have a smoothly rounded surface, without any trace of sagittal crest or area, or temporal ridges. The supraoccipital is extended farther upon the dorsal surface of the cranium than in Cama. The body of the squamosal is larger than in the recent genera, but the supramastoid process is nar- rower and there is no such groove above the root of the zygomatic process as is seen in Dolichotis. The zygomatic arch is more elongate and the jugal is longer and more slender than in the recent genera, as in which it does not extend to the lachrymal ; in shape it has more resemblance to that of Cavia. The 464 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. lachrymal is considerably smaller than in either of the existing genera. The frontals are but slightly convex, without protuberances for the sinuses ; the supraorbital border is thin and prominent, but entire, without notch ; the postorbital process corresponds in position to that of Dolichotis, but is somewhat shorter. The nasals are elongate and broad and their anterior portion is transversely convex ; the free ends resemble those of Cavia in being bluntly pointed, without deep lateral notches. The premaxillaries are shorter than in the modern genera, and the edentulous portion of the maxillaries longer, making up nearly half of the FIG. 45. Skulls of Caviidae, left side. a. Dolichotis magellanica, x \. b. Cavia cobaya, x |. c. Eocardia excavata, x \. rostrum ; the incisive foramina are larger and invade the maxillaries more deeply. The hard palate is quite different from that of the existing genera; it narrows anteriorly much less, as is determined by the lesser de- gree of convergence of the dental series, and is more extensively made up by the much larger palatines, and is much less reduced by the posterior nares, which are smaller, extending only to m-, and are of a different shape, with more nearly parallel sides and with a median spine from the anterior border. The pterygoid fossae are large, but I have not been able to de- GLIRES OF THE SANTA CRUZ BEDS. 465 termine whether they are perforated so as to communicate with the orbits. This skull agrees with that of Dolichotis in the moderate size of the fora- men lacerum medium, there being no such great vacuity at this point as occurs in Cavia. The mandible has a general resemblance to that of Dolichotis, but, as Ameghino has pointed out, Eocardia differs from all the existing mem- bers of the family in the position of the masseteric crest. In the recent genera the crest has a very elevated position and an almost horizontal course, with a deep groove between itself and the alveolar border, but in the fossil the crest is much lower down on the jaw and runs obliquely downward and backward, forming the ventral border of the angle. The coronoid process, though very much reduced, is better developed than in Dolichotis and rises higher than in Cavia, though, owing to the shal- lowness of the sigmoid notch, it appears to be shorter ; the condyle has much the same shape as in the former, as has also the masseteric fossa. The angular process has been broken and lost from all the specimens. The horizontal ramus is quite stout and its ventral border has several protuberances for the teeth, which, however, are far less conspicuous than in Dolichotis ; the symphysis is shorter and less procumbent than in the latter, the chin rising much more steeply. Vertebral Column and Ribs (Plate LXXI). — The neck is rather short and slender. The atlas is short, broad and depressed, without neural spine and with only a vestige of the hypapophysis ; the transverse pro- cesses also are short in both dimensions and are less produced behind the posterior cotyles than in Dolichotts. The neural spine of the axis is relatively considerably smaller than in the latter, but of not dissimilar shape ; the centrum is short and much depressed, the cotyles for the atlas rising high upon the sides of the large neural canal. The other cervicals are small and lightly constructed, but without other peculiarity than the absence of neural spines from the third, fourth and fifth. The number of trunk vertebrae has not yet been definitely determined, though there is reason to believe that it was the same as in Dolichotis, Th. 12, L. 8, but, owing to the disparity in the length of the fore and hind limbs, the curvature of the back is different. In the anterior part of the thoracic region the neural spines are considerably shorter than in the recent genus, are very slender and have a strong backward inclination ; posteriorly the spines diminish in length and increase in width, while the 466 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. centra are enlarged. In the lumbar region, especially its hinder part, the centra are very large, indicating powerful and muscular loins ; the neural spines, which increase in length posteriorly, are not much shorter, pro- portionately, than in the existing genus, but much more slender, and have a strong forward inclination ; the metapophyses and anapophyses, on the other hand, are much more prominent, while the transverse processes are quite similar in the two genera. The sacrum also is much like that of Dolichotis, but consists of only three vertebrae, the first of which alone is in contact with the ilia; the second and third vertebras have very long and slender, cylindrical centra ; the spines, which are separate, not fused into a continuous ridge, are elongate, though shorter than in the modern genus. The short tail also is very much as in the latter, but is slightly longer and thinner, and the spines of the anterior caudals are not so long. Chevron bones were prob- ably present, though none have been found. The ribs, especially in the anterior part of the thorax, are much more slender and rod-like than in Dolichotis. The sternum is not known. Appendicular Skeleton. — The scapula is relatively smaller than in Doli- chotis and differs somewhat in shape; the coracoid border describes a wider curvature, making the prescapular fossa wider, and the glenoid border is more elevated ; the incisura colli is very long, while the acro- mion has an even greater antero-posterior expansion, but this expansion is less sudden and the posterior process, though nearly as long as in Cavia, is much broader. The coracoid is a well developed, incurved hook, but hardly so prominent as in Dolichotis. The pelvis differs from that of Dolichotis in a number of details, as well as in its greater lightness and slenderness of construction. The ilium has a short peduncle, expanding suddenly into the large anterior plate, which is strongly everted ; the prominent acetabular border has a more inferior position than in the existing genus, making the gluteal surface wider and more concave, and the iliac surface, which is more lateral than ventral, is narrower than in the recent genus and the ilio-pectineal process is much more prominent ; the acetabulum is small and subcircular, with projecting border. The ischium, which is much shorter than the ilium, is laterally compressed and has an unusually deep and conspicuous sciatic notch ; the tuberosity is smaller and less prominent than in Dolichotis and the descending process of the ischium is narrower, while the obturator fora- GLIRES OF THE SANTA CRUZ BEDS. 467 men is of more irregularly quadrate, less oval form. The pubis is quite elongate, thin and laterally compressed ; it forms a long symphysis with its fellow of the opposite side. There is much more disparity between the lengths of the fore and hind limbs than in any existing member of the family. The humerus (Plate LXIX, fig. 4) is very short and slender, but, except in size, has a close resemblance to that of Dolichotis ; the tuberosities are reduced, the external one not rising above the level of the head, but is quite broad transversely ; the shaft is slender and the deltoid ridge is but weakly developed. The distal end is narrow and the epicondyles nearly obsolete ; there is no epicondylar foramen ; the trochlea, the whole breadth of which is occupied by the radius, has the usual division into three parts, of which the median convexity is more prominent than in the recent genus ; the anconeal and supratrochlear fossae are deep and connected by a perforation. No difference between Rocardia and Dolichotis is more striking than the great elongation of the fore-arm in the latter and its shortness in the former ; instead of far exceeding the humerus in length, as it does in the modern genus, it is considerably shorter, so that the segments of the fore limb have more the proportions seen in Cavia. The radius (Plate LXIX, fig. 5) is very slender; the proximal end is broad, occupying the whole humeral trochlea, with which it is so inter- locked as entirely to prevent any movement of rotation. The shaft, which js antero-posteriorly compressed, is less strongly arched forward than in Cama, and the distal end is but moderately expanded and has a shallow tendinal sulcus on the anterior side. The ulna, though far shorter, is much stouter than in Dolichotis and has a shorter olecranon ; the sigmoid notch is deep, describing more than a semicircle, and the shaft is as stout as that of the radius, quite as thick as in Cavia, but less curved ; the distal end bears a narrow, convex facet for the pyramidal. Of the manus (Plate LXIX, fig. 6) only the metacarpus and a few phalanges are known, but these suffice to show that it was very small. Almost certainly the number of digits is four. The functional metacarpals have the same arrangement as in the recent members of the family in two symmetrical pairs. Metacarpal II is short and slender, moderately ex- panded at the proximal end ; as in Dolichotis, it has three carpal facets, 468 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. but the proportions are different, that for the trapezoid being the largest, while in the modern genus the facet for the trapezium is much the largest and the contact with the magnum is -more extensive than in the fossil. The nearly straight shaft is of transversely oval section ; the distal trochlea is low and semicylindrical and has a low carina. Metacarpal III is much longer and stouter than II ; on the radial side the proximal end is over- lapped by that of II, but less extensively than in Dolichotis and the con- tact with the unciform is also smaller. The shaft is straight, antero- posteriorly compressed and broadening slightly toward the distal end. Metacarpal IV resembles III in length and thickness ; it has but a com- paratively narrow contact with the unciform, because of the manner in which III extends over it. Metacarpal V, which is considerably the shortest of the series, has a relatively wide proximal end, with a process from the fibular side which is not present in Dolichotis; the shaft is stout and somewhat curved. Only a few phalanges have been found and these resemble the corre- sponding bones of Dolichotis on a very small scale. The femur (Plate LXIX, fig. 8) is considerably shorter than in Doli- chotis as compared with the size of the skull, but much longer in com- parison with the humerus. The head is small, very symmetrically hemispherical and placed upon a very slender neck ; the pit for the round ligament is very small and obscure ; the great trochanter, though large, is much smaller than in the recent genus, as is also the digital fossa ; the second trochanter is less prominent than in the existing type and there is no trace of a third trochanter. The shaft is stout and somewhat com- pressed antero-posteriorly ; the condyles are shaped very much as in Dolichotis, but the rotular trochlea is narrower and more symmetrical, the outer border rising as high as the inner. The patella is not unlike that of Dolichotis, but is narrower and espe- cially thinner, with much less rugose anterior face. As in the fore-arm, so in the leg, the bones of Eocardia are relatively far shorter than those of Dolichotis, though exceeding the ulna and radius in length to a much greater degree. The tibia (Plate LXIX, fig. 9) is but little longer than the femur and nearly twice as long as the radius, while in the modern genus both radius and tibia are remarkably elongate. In form, the tibia is much like that of Dolichotis, except for its greater slen- derness and the smaller development of the cnemial crest ; the proximal GLIRES OF THE SANTA CRUZ BEDS. 469 condyles are widely separated by the broad sulcus for the crucial liga- ment, and the hook-like process from the postero-external angle of the outer condyle is smaller than in the recent genus. The distal end has an asymmetrical surface for the astragalus, with much larger external con- dyle, prominent intercondylar ridge, which is invaded by a sulcus from the dorsal side, and very large posterior tongue ; the internal malleolus is small, but distinct. The fibula is very much less reduced than in Dolichotis and is even relatively stouter than in Cavia; the proximal end is narrow, but thick antero-posteriorly, the shaft is very irregular and the distal end forms a heavy external malleolus, grooved by the sulcus for the peroneal tendon on the outer side. The pes (Plate LXIX, fig. 10) though far larger than the manus, does not exceed it so much as in Dolichotis and has more the proportions seen in Cavia; in structure it resembles that of the former genus, with several minor differences, the tarsus resembling that of Cavia. The calcaneum has a short heavy tuber, of trihedral shape, broad on the plantar side and contracting to a blunt edge on the dorsal ; the external astragalar facet is large, convex and very oblique, presenting inward ; the sustentaculum is heavy and not very prominent, with small, subcircular facet ; the cuboid facet is deeply concave and very oblique, presenting inward rather than distally. The astragalus differs considerably from that of Dolichotis, especially in the narrowness of the neck and head and in the absence of the deep pit distal to the trochlea which is seen in the modern genus ; the trochlea is very asymmetrical, owing to the large size of the outer con- dyle, and is quite deeply grooved. The navicular also is much narrower than in the last-named genus and the cuboid far shorter proximo-distally, and thicker planto-dorsally, but has a similar massive process from the whole plantar side, to the distal end of which is attached a sesamoid bone, just as in the modern genus ; the facet on the distal end for metatarsal V is minute. The meso- and ectocuneiforms, especially the latter, are smaller than in DolicJiotis ; the entocuneiform has not been found, but its presence is demonstrated by the facets upon the second metatarsal. It is almost certain that the number of functional metatarsals is three; these are very much larger than the metacarpals. Metatarsal II is long, relatively slender and asymmetrical ; owing to the small size of the meso- cuneiform, its proximal end rises much above that of III, as is universal in 47° PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. the rodents, and has an extensive lateral contact with the ectocuneiform ; on the tibial side is an oblique bevelled surface for the entocuneiform, the shape of which makes it probable that no vestige of the hallux was retained. The shaft is slender, subtrihedral and curved, with concavity toward the tibial side, expanding slightly toward the distal end. Metatarsal III is the longest and heaviest of the series and its apparent length is increased by its position in the foot, the proximo-distal length of the ectocuneiform so much exceeding that of the mesocuneiform, on the one hand, and that of the cuboid on the other. The tarsal facet is nearly plane and horizontal, without obliquity ; the shaft is straight, broad and antero-posteriorly compressed, widening somewhat to the distal end ; the trochlea is low, shorter proximo-distally than in Dolichotis and the supra- trochlear fossa is smaller. Metatarsal IV is the counterpart of II in size and shape, but is somewhat more curved ; on account of the extreme shortness of the cuboid, the head of this metatarsal rises higher above that of III than in the modern genus. On the fibular side of the head is a large depression and a very small articular surface, evidently for the rudi- mentary fifth metatarsal and, no doubt, this rudiment had much the same shape and relative size as in Dolichotis. In proportion to the length of the metatarsals, the phalanges of the first row are more elongate and slender than in Dolichotis, though, like all parts of the limbs and feet, they are smaller in comparison with the head and vertebral column. The unguals are quite different from those of the recent genus, being more curved, slender and sharply pointed, with smaller distal cleft, and altogether more claw-like ; the subungual process is very large and prominent. Restoration (Plate LXXI). — The resemblance between the skeleton of Eocardia and and that of Dolichotis is obvious at the first glance, but there are many minor differences in all parts. The skull has a shorter, thicker and wider rostrum, and the symphysial region of the mandible is less procumbent. The neck is shorter and lighter and in the trunk the vertebral column has quite a different curvature, owing to the greater disparity in length between the fore and hind limbs, while in the lumbar, sacral and caudal regions the neural spines are shorter and much more slender. The tail is somewhat longer and thinner, and the ribs are thinner and less plate-like, making a smaller and lighter thorax. The limbs are much shorter and the feet smaller and, in particular, the fore GLIRES OF THE SANTA CRUZ BEDS. 471 limbs are very much less elongate ; on the other hand, the hind limbs exceed the fore much more than in Dolichotis, in which the anterior and posterior extremities are of nearly equal length. The gait, it may be inferred from the structure of the feet, was completely digitigrade. In brief, it would hardly be inaccurate to describe Eocardia as a smaller, lighter and shorter-limbed Dolichotis. In the following comparative table the distance from the occipital con- dyle to the premolar, inclusive, is taken as 100 and the other dimensions are calculated in percentages of that distance. This standard is chosen rather than the entire length of the skull, because it eliminates the differ- ent proportions of the rostrum. MEASUREMENTS. Schistomys ellipticus, Distance, occipital condyle to pA inclusive 100 (49 mm.) Scapula length 109.6 Pelvis, length Humerus, length 1 26. 5 Radius, length Ulna, length Metacarpal III, length Femur, length from great trochanter. . . 171.4 Tibia, length 175-5 Tarsus, length Metatarsal III, length 63.2 Phalanx I, digit III, length Relationships. — Though Eocardia is probably not ancestral to any existing genus, it is, nevertheless, a type of great interest and importance, for it brings before us, in somewhat modified shape, the common ancestral form of Dolichotis and Cavia and possibly even of Hydroch&rus also. In comparing the two former genera, we see that Cavia has the more highly differentiated dentition and Dolichotis the more specialized skull, limbs and feet. Eocardia shows the beginning of the Cavia type of grinding teeth in the shallow accessory enamel folds and in the presence of cement. In the latter, however, only one such fold is deepened and made permanent in each tooth, while Eocardia has three, and this gives at least a hint of the manner in which the highly complex molars of Hy- drochcerus have arisen ; in Dolichotis the teeth have been simplified by the Eocardia Dolichotis excavata. magellanica. loo (47mm.) loo (70 mm.) 91.4 121.4 I53-I 201.2 110.5 165.7 87 214.2 112.7 250 34-8 58-5 144.6 184.2 148.9 230 44.6 75-7 51 97.1 25-3 32.4 472 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. loss of the accessory enamel folds, reducing the crown to two simple prisms. Luaiitlins, a genus from the Patagonian beds, in which the grind- ing teeth are all rooted and the accessory folds are much deeper vertically than in Eocardia, nearly or quite represents the common stock whence all the existing members of the Caviidce have been derived ; its tooth-pattern shows that already in Eocardia the accessory folds were in process of dis- appearance. Synonomy. — Ameghino originally referred all the species to the single genus Eocardia ; later ('91, 302) he established four subgenera, Eocardia, Procardia, Dicardia and Tricardia, upon the differences in the form of the lower premolar, and finally he raised these to the rank of genera ("94", 74). As will be shown in a succeeding section, Procardia very unexpectedly proves to be a synonym of Schistomys, while, as already pointed out, the variations, both individual and specific, in the form of p? are so great and the transitions between the extremes is so complete, that, in my judgment, it is both impracticable and unnecessary to divide the genus. Hedimys was established upon a single tooth, which, I am con- fident, is the milk premolar of Eocardia. I have found great difficulty in referring the large number of specimens of Eocardia in the Princeton and New York collections to the species already described, because so few of them agree at all closely with the types and because they connect the supposedly distinct species by such gradual transitions. It will therefore be necessary either to increase largely the number of species, or considerably to reduce the number already named. In view of the demonstrated individual variability, reduction is undoubtedly the proper course. EOCARDIA MONTANA Ameghino. (Plate LXIX, Figs, i, i«.) Eocardia montana Amegh. ; Observ. gen. sobre el Orden de los Toxo- dontes, etc., La Plata, 1887, p. 65. Dicardia maxima Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 302. Dicardia proxima Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 74. As this, the type species, was established upon a single tooth, which is insufficient for specific identification, it will be necessary to regard as types GLIRES OF THE SANTA CRUZ BEDS. 473 the individuals which Ameghino described and figured in his great work ('87*, p. 214, PI. X, figs. 8-1 1). The species is one of the larger and more robust members of the genus ; the incisors are relatively large and stout and m- has a long, incurved posterior process. The lower premolar is very variable in form ; the anterior prism may be smaller, or larger than FIG. 46. c Eocardia montana, lower grinding teeth, x f . a. Right side, crown view. b. Right side, external and crown views, A. M. N. H. c. Left side, crown view, A. M. N. H. the posterior, of elliptical, elliptico-triangular, or triangular cross-section, and with or without a groove on the anterior face ; when present, the groove is shallow. In one individual (Fig. 46, b, A. M. N. H., No. 9,526) there is a low, but quite distinct pillar on the anterior prism, set off by a fine hairlike groove on each side of it. The mandible is stout. One specimen (No. 15,385) which I refer to this species, though of unusually small size, consists of a much flattened skull, lacking the cranial roof and mandible, and several fragments of vertebrae and limb-bones. The absence of the mandible makes the reference somewhat uncertain. The specimen is remarkable for the small size of p-, for the heavy rostrum, which tapers anteriorly, and for the thickness of the zygomatic arch, espe- cially of the zygomatic process of the maxillary. MEASUREMENTS. No. No. No. 15,574- 9,526. 15372. Lower dentition, length 039 .039 " " " pT-nij 019 .018 .019 Lower incisor, width 003 .003 " " thickness 004 .0x335 Pf, length (i. e., antero-posterior diameter) 0x34 .0x34 .004 " width (/'. e., transverse diameter of anterior prism) 0025 .0025 .0x325 Mandible, depth at pj OIO .010 .010 " length from condyle .050 The following measurements are from the specimen of doubtful refer- ence, mentioned above (No. 15,385) : 474 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. Upper dentition, length 037 Palate, width at p± 005 " " " p4-m* 0165 " " "ml oio Upper incisor, width 003 Humerus, distal width 0095 " " thickness 0035 " width of trochlea 007 Pi, length 0025 Radius, proximal width 006 " width 003 Femur, " " 018 Skull, length, occipital condyle to pre- " distal " 013 maxillary 072 Tibia, proximal width 015 Rostrum, width at base 014 " " thickness 012 " " " anterior end 009 EOCARDIA EXCAVATA (Ameghino). (Plates LXVIII, Fig. 25 ; LXIX, Figs. 3-10.) Dicardia excavata Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 302. Tricardia gracilis Amegh. ; Ibid. The following description is founded upon the types in the Ameghino collection and upon the most complete individual respresentative of the genus which has yet been found. This specimen (No. 15,211), a nearly entire skeleton, was collected by Mr. Hatcher on the Atlantic coast of Pata- gonia, ten miles south of Coy Inlet. The average individual of this species is smaller and slighter than E. montana, though connecting variations in regard to size are such that the difference is by no means striking ; the incisors are more slender, but p- is larger, while m1 has a decidedly smaller posterior process. PA is very variable, as is shown by the difference between the two sides of the same mandible ; the anterior prism is usually, but not always, larger than the pos- terior and has a deep groove on the anterior face, which is sometimes so deep as to produce three well denned external, vertical crests (Tricardia]. In No. 15,21 1 this groove is much better denned on the left side than on the right, and it would be no great exaggeration to say that in this individual the right half of the mandible belonged to E. excavata and the left to Tricardia gracilis. The skull is not very completely known in this species, for in the nearly entire specimen (No. 15,211) almost the whole top of the skull has been weathered away and what remains has been considerably distorted by pressure. It is plain, however, that the skull is relatively narrower and more elongate than in E. montana, that the zygomatic arch, especially GLIRES OF THE SANTA CRUZ BEDS. 475 the ventral branch of the maxillary zygomatic process, is more slender and that the rostrum is longer and narrower. The mandible has low and narrow horizontal rami. An account of the bones of the skeleton has already been given in the generic description, which is principally taken from this particular speci- men, though in several other species more or fewer of the limb bones FIG. 47. CL Eocardia excavata, lower grinding teeth, external and crown views, x |. a. Right side. b. Left side of same individual (No. 15,211). have been obtained and serve for purposes of comparison. Aside from the size and slenderness of the bones in this species, the only character which should be emphasized is the stoutness of the fibula, which has a thicker shaft than in E. perforata. In the following table all the dimensions are taken from the skeleton, No. 15,211. MEASUREMENTS. Upper dentition, length pA-mS- 017 Mandible, length from condyle 045 Upper incisor, width 0025 ." depth at p^ ' .008 Atlas, length oio " width 02 1 Axis, length of centrum 009 " width of anterior face Ol I " height to tip of spine 017 Lumbars 5-8, inclusive, length 064 Last lumbar, width of posterior face . . .009 " thickness 003 P±, length (/. e., antero-posterior diam- eter) 003 PA, width (i. e., transverse diameter). . .0026 M-3-, length 005 " width 004 Lower dentition, length 0345 " P5-m3 OI75 Lower incisor, width 0025 " " thickness 003 P?, length 0035 " width of anterior prism 003 Occiput, height 017 " " width at base 022 Zygomatic arch, length 035 Palate, width at p*. 0055 " " " m^. . .008 Last lumbar, width over transverse processes ?-O3O Sacrum, length 03 1 " width over pleurapophyses . . .027 Scapula, length 043 " greatest width 02 1 " distal width oil Humerus, length 052 " proximal width 009 " distal width 009 476 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. Ulna, length 053 Radius, length 041 " proximal width 006 " distal width 006$ Metacarpal II, length 013 " " proximal width 003 Metacarpal III, length 016 " " proximal width 003 Metacarpal IV, length 015 Metacarpal V, length oio " " proximal width 003 Pelvis, length 7.072 Ilium, length 043 " greatest width 014 Ischium, length ?.O2g Symphysis, length 024 Femur, length from head 0645 " " great trochanter.. .068 proximal width 017 " distal width 013 Tibia, length 075 " proximal width 013 " " thickness. , 012 Tibia, distal width 008 Fibula, length 067 " distal width 004 " " thickness 005 Tarsus, length 02 1 Astragalus, length on " width of trochlea 006 " " " distal end 004 Calcaneum, length 018 Metatarsal II, length 023 " " proximal width 0035 " " distal width 0035 Metatarsal III, length 024 " " proximal width 0045 " " distal width 0045 Metatarsal IV, length 022 " " proximal width 003 Digit II, phalanx I, length on " " " " proximal width .. .014 " III, " " length 013 " " " 2, length 005 " " " 3, length 009 "IV, " i, on FIG. 48. EOCARDIA MODICA (Ameghino). Dicardia modica Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 302. It is not yet possible to determine whether this is a valid species or merely a variant, and it is therefore provisionally retained. To it I refer a mandible (A. M. N. H., No. 9,526), which agrees well with the type. In size this species is some- what less than R. excavata; pT has a very charac- Eocardia modica. left • ,• ,\ . . . « . ,, tenstic appearance, the anterior prism being: small, lower grinding teeth, ex- l ternal and crown views, perfectly triangular and with the groove of the x f A. M. N. H. anterior face broad and shallow. MEASUREMENTS. Lower dentition, length pt-mj 016 Pj, length (/. e., antero-posterior diameter) .003 P?, width of anterior prism 002 Mandible, depth at p^ 009 GLIRES OF THE SANTA CRUZ BEDS. 477 EOCARDIA PETERSONI, sp. nov. The type of this species, a left ramus mandibuli (No. 15,323), was found ten miles south of Coy Inlet by Mr. O. A. Peterson, to whom the species is dedicated. It differs markedly from all the other species in the form of the valleys, at least in the lower teeth. In the other species the valley ends internally in a simple, narrow, cement-filled cleft, but in the present species the valley of the lower molars is divided internally into two short, divergent branches ; in mT and nw & FIG. 49. the prominence which separates the branches is symmetrical and placed in the middle of the tooth, but in nig it is asymmetrical and both branches curve forward into the anterior prism. This arrange- .. , . Type of Eocardia petersoni, left mandibular ment persists for a long time, but ramus> crown view> x f eventually wears away, as is evident from a comparison of the three molars. The type is from a fully adult, rather old animal and p¥ has no indication of the divided valley. The outer edges of the prisms of the molars are set off as pillars with quite unusual distinctness. The mandible is rather short and heavy, with prominent masseteric crest and external border of the masseteric fossa. In size E. petersoni agrees closely with E. montana, but is not likely to prove a variation of that species, for none of the specimens of the latter show any tendency to vary in that direction. MEASUREMENTS. Lower dentition, length 038 PT( length (i. e., antero-posterior diam- p^-m, 0175 eter) 0035 Lower incisor, width 003 P^, width of anterior prism 0025 " " thickness 0035 Mandible, depth at p? oio EOCARDIA PERFORATA Ameghino. (Plates LXVIII, Figs, 23-23" ; LXIX, 2, 2°.) Eocardia perforata Amegh.; Enumeracion sistem., etc., 1887, p. 13. Eocardia fissa Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 146. Dicardiafissa Amegh. ; Enum. Synopt des Mamm. Foss. de Patagonie, 1894, p. 74. 478 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. This species is distinguished by its smaller size and more delicate pro- portions. PA varies much in size, but has constantly a prominent ante- rior pillar, which is set off by grooves on each side, and is better devel- oped than in E. montana, or excavata ; the posterior process of m- is also variable, but is constantly smaller than in E. montana and may be quite rudimentary. PT is small, the anterior lobe smaller than the posterior and grooved, though, as usual, this groove varies much in depth and dis- tinctness. The skull is elongate and slender, notably lighter than that of E. montana. Several limb bones were found in association with one of the skulls ; they resemble those of E. excavata in form, but are somewhat lighter and smaller; the only important difference is the greater reduction of the fibula in E. fier/orata, the shaft being extremely slender. MEASUREMENTS. No. 15,010. No. 15,463. Upper dentition, length 035 lf " pA-mi 0145 .0145 Upper incisor, width 0025 .0023 " " thickness 0033 .0033 P-*., length (i. e., antero-posterior diameter) 003 .003 " width (i. e., transverse diameter) 0035 .003 Lower dentition, length 035 " Pr-m* OIS Lower incisor, width 0023 .0023 " " thickness 0025 .003 P?, length 003 .003 " width of anterior prism 002 .002 Skull, interorbital width 0165 Rostrum, length 019 " width at base oil " " " anterior end 009 Palate, width at p*. 003 .003 " " " m-3- 0075 .007 Mandible, depth at pj 009 .008 Scapula, antero-posterior diameter of glenoid cavity .007 Femur, length from head .061 " " " great trochanter .064 " proximal width .015 " distal width .012 Tibia, estimated length .072 " proximal width .on " " thickness . . .012 GLIRES OF THE SANTA CRUZ BEDS. 479 EOCARDIA DIVISA (Ameghino). (Plate LXVIII, Fig. 24.) Eocardia divisa Amegh. ; Enumeracion sistem., etc., 1887, p. 13. Tricardia divisa Amegh. ; Rev. Argent, de Hist. Nat., T. I, 1891, p. 302. Tricardia crassidens Amegh. ; Ibid., p. 303. The type of this species I have not seen and am therefore unable to speak confidently of its status. It is the largest known representative of the genus, the lower grinding series being 23 mm. in length. The lower incisor is somewhat longer than in E. montana and extends to nvj. PT appears to be constantly divided into three external crests, the anterior one of which may become a small, subcircular pillar. SCHISTOMYS Ameghino. (Plates LXVIII, Figs. 26-26"; LXIX, n-i86.) Schistomys Amegh. ; Enumeracion sistem., etc., 1887, p. 13. Eocardia Amegh.; in part; Rev. Argent, de Hist. Nat., T. I, 1891, P- 145- Procardia Amegh. (subgenus) ; Ibid., p. 302. Procardia Amegh. (genus) ; Enum. Synopt. des Mamm. Foss. de Pata- gonie, 1894, p. 73. This very well marked and distinct genus is closely allied to Eocardia, but with several important differences, which may be noted in all parts of the skeleton. The incisors tend to be heavier, though the difference is not striking; p- (Plate LXIX, fig. i id] is molariform and is composed of two triangular prisms, which are a little thicker and separated by a some- what shallower valley than in the molars ; m^ is decidedly variable in form and in the size of its posterior process, which is straighter and less incurved than in Eocardia. In the unworn teeth the three external valleys are present, just as in the latter genus, and are soon isolated by wear as enamel lakes and then disappear altogether. All the upper grinding teeth are more strongly curved than in Eocardia, so that the masticating surfaces present more obliquely outward. The two dental series converge forward somewhat more strongly than in the latter, and their grinding surfaces have a forward and downward inclination, which is almost as decided as in Dolichotis. 480 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. The lower premolar (fig. i irf) is, strange to say, less completely molari- form than in Eocardia; the external valley which separates the prisms is not continued for the whole height of the crown, but is, in not very advanced stages of wear, converted into a central lake and is then worn away entirely. The molars resemble those of Eocardia, but, so far as I can make out, there is no cement in the valleys of either upper or lower teeth. The milk premolars (Plate LXVIII, figs. 26-26") differ from those of Eocardia principally in being rootless ; dp1 resembles its successor, includ- ing the external accessory valleys, but dpT is more complex than pT and is much more elongate antero-posteriorly ; the anterior prism is subdivided by a second external valley, which is shorter and shallower than the principal one and, in the stage figured, is reduced to a mere notch of the grinding surface. The skull (Plate LXIX, figs. 11-12) resembles that of Dolichotis even more than does that of Eocardia, especially in the breadth of the cranium, the large size of the orbit and the manner in which the face is bent down upon the cranial axis, so that the palate is not parallel with that axis, but forms an obtuse angle with it ; this flexure is, however, less than in Dolichotis. The occiput (fig. 12*) is lower and wider than in the last- named genus, narrowing less toward the summit, and the foramen magnum and condyles are correspondingly lower and wider; the paroccipital processes are similar, except for being much more slender; the supra- occipital is much less extended upon the cranial roof. The parietals have much the same broad and vaulted appearance as in Dolichotis, but the upper contour of this region does not descend so much from the coronal suture to the occipital crest, which is principally due to the less pronounced character of the cranial flexure ; the sagittal crest is relatively somewhat longer than in the modern genus, but is very low and inconspicuous. The tympanic bullae are smaller than in the latter, especially in the transverse diameter, so that they narrow the basicranial axis less. The periotic is almost identical in shape and relations with that of Dolichotis, but the part left uncovered by the supramastoid process of the squamosal is somewhat larger and more inflated, and the mastoid process, though very small, is less reduced. The squamosal, though very much like that of Dolichotis, differs from it in a number of details ; anteriorly, it is much less extended along the GLIRES OF THE SANTA CRUZ BEDS. 481 floor of the orbit, and dorsally less of it appears upon the cranial roof; the supramastoid process is both longer and wider, but is less expanded at the posterior end, and there is no such groove above the root of the zygomatic process. The latter process is longer, overlapping the jugal more extensively and articulating with it by a simple, almost straight suture. The jugal is longer and narrower dorso-ventrally, but of similar laterally compressed, plate-like structure ; anteriorly, it ends in a sharper point which penetrates much farther into the zygomatic process of the maxillary, but is farther removed from the lachrymal. The ventral branch of the maxillary zygomatic process is much more slender and is far more deeply notched to receive the jugal. The lachrymal is considerably smaller, but has a similar triangular shape and very low spine. The frontals are broad, moderately convex and smooth, without protuberances for the sinuses ; the orbit is deep and the supraorbital border prominent and may or may not be notched ; if present, the notch is much shallower than in Dolichotis ; the postorbital process, which is incomplete in all of the skulls, may have been no longer than in the recent genus, but is more prominent, being directed outward, instead of downward. The anterior end of the frontal region has simpler sutures than in Dolichotis and there is hardly any nasal process. The nasals are longer than in the modern genus; in breadth and degree of convexity they differ in the various species ; the anterior ends, which are not preserved in any of the specimens, were probably shaped as in Eocardia. The rostrum is relatively somewhat shorter and broader and tapers less anteriorly than in Dolichotis, but in the proportions of the rostrum decided differences may be noted between the various species. The premaxillaries are shorter than in the existing genus, but the ascending processes, which articulate with the frontals, are longer. The maxillaries differ from those of the modern genus in several respects : the edentulous portion, in front of the grinding teeth, is longer, making up more of the rostrum, and is more deeply invaded by the much larger incisive foramina ; the masseteric fossa is much deeper, though of similar shape, and the alveolus of m3- pro- jects less conspicuously into the orbit. The palate is less triangular than in Dolichotis, but rather more so than in Eocardia, and differs from that of the latter in having shorter palatines and larger maxillary elements. The posterior nares are wider than in Eocardia, with walls diverging more posteriorly ; the pterygoid fossae are large and perforated at the bottom, 482 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. opening into the orbits. The alisphenoid has a broad, horizontal surface, internal to the squamosal, which differs from that of Dolichotis in its greater size and in the presence of a large foramen ovale, which in the modern genus has coalesced with the foramen lacerum medium. The mandible does not differ in any important respect from that of Eocardia. Two of the skulls have considerable parts of the skeleton associated with them, unfortunately including but few vertebrae and no ribs or parts of the sternum. The atlas and axis are so like those of Eocardia as to require no description. The lumbars are larger than in the latter and have broader spines and transverse processes, being in all respects, except for the prominence of the anapophyses, more like those of Dolichotis, though the neural spines are more slender and more strongly inclined forward. The sacrum differs from that of Eocardia only in its larger size. The scapula (Plate LXIX, fig. 13) is not only larger than in Eocardia, but of a somewhat different shape, being broader in proportion to its length and with more convex coracoid and suprascapular borders ; the acromion is more recurved and the metacromion more slender ; the neck is more contracted ; the coracoid is large and prominent, but is curved so directly inward as to be concealed when the scapula is seen from the side. In both of the Santa Cruz genera the acromion is considerably larger than in Dolichotis, descending below the level of the glenoid cavity. So much of the pelvis as is preserved resembles that of Eocardia. All of the limb-bones are larger than in Eocardia, as compared with the size of the skull, but the disparity in the length of the fore and hind limbs is even greater, a marked difference from Dolichotis. The humerus (PI. LXIX, fig. 14), though very like that of Eocardia, differs in the less developed deltoid crest and in the wider distal end, due to the greater prominence of the internal epicondyle ; in the trochlea, the median con- vexity for the head of the radius is shifted somewhat farther toward the outer side, and the supratrochlear foramen is larger. Of the fore-arm bones only fragments have been obtained ; these are remarkably slender and indicate that the ulna and radius could have had no such elongation as in Dolichotis ; in shape they resemble the corre- sponding parts of Eocardia.' The femur (PI. LXIX, fig. 15) is relatively much longer and heavier than in the other Santa Cruz genus and the great trochanter rises higher GLIRES OF THE SANTA CRUZ BEDS. 483 above the level of the head, which is situated upon a longer and more constricted neck. The shaft is heavy, broad and antero-posteriorly compressed. The tibia (PI. LXIX, fig. 16) is merely an enlarged copy of that of Eocardia, with somewhat straighter shaft. The fibula has a complete though very slender shaft, which is more reduced than in E. excavata ; the distal end is shaped as in that species. The astragalus is more asymmetrical than in Eocardia, owing to the larger size of the external condyle, and the distal end is broader and more depressed, an interesting approximation to Dolichotis. The only other elements of the pes which have yet been found are the distal half of the calcaneum and metatarsals II and III, and a few phalanges ; all of these are so like the corresponding parts of Eocardia that description would be superfluous. Relationships. --There can be little doubt, I think, that in Schistomys we have the direct ancestor of Dolichotis. The only objection to this conclusion that might be urged is the disparity in the length of the fore and hind limbs in the fossil. We know of no reason, however, why in the evolution of a phylum the hind limb should not first increase in size and then, at a later stage, the fore limbs lengthen equally. This same process has been observed in other phyla, notably that of the horses, in which the Oligocene Mesohippus shows a similar disparity that, in subse- quent genera, is removed by the elongation of the fore limb, and as already mentioned, in the Prolagostomus — J/iscaccia series. SCHISTOMYS ELLIPTICUS (Ameghino). (Plate LXIX, Figs. 11-16.) Eocardia elliptica Amegh. ; Rev. Argent, de Hist. Nat. T. I, 1891, p. 145. Procardia elliptica Amegh. ; Ibid., p. 302. Schistomys crassus Amegh. ; Ibid., p. 303. This species is distinguished by its larger size and generally more advanced state of differentiation ; in size there is considerable variation and it is evident that, as in certain existing -rodents, growth continued till quite a late period in life. P1 is large, nearly as large as m1 and the grinding surface of the upper teeth has a strong inclination downward and forward. The cranium is high and vaulted, with upper contour decid- 484 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. edly arched in the antero-posterior direction ; the supraorbital border is thin and notched. The face is strongly bent down upon the cranial axis, and the rostrum is relatively short and narrow. The limb bones have already been described. In the subjoined table No. 9,539 is a specimen in the collection of the American Museum of Natural History. MEASUREMENTS. No. No. No. No. 15,64.8. 15,420. 15,620 0,530. Upper dentition, length .041 " " " pA-m-3- 0173 .018 .017 Upper incisor, width .003 " " thickness .0042 PA, length (i. e., antero-posterior diameter) 004 .004 -0035 " width (i. e., transverse diameter) 004 .004 .004 Lower dentition, length 039 " PT-I% 019 Lower incisor, width 003 " " thickness 003 5 Skull, length occipital condyle to pj-, inclusive. . . .049 " " " mT " ... .045 .052 Occiput, height 023 .023 " width at base 028 .029 Tympanic bulla, length 014 .014 Skull, interorbital width 024 .024 .021 .022 Zygomatic arch, length 032 .035 -037 Rostrum, length .023 Palate, width at pi 0035 .003 .003 " " " m8- 009 .009 .0095 .o 10 Mandible, length from condyle 052 " depth at p*. on Atlas, length .on width .026 Axis, length of centrum .012 " width of anterior face .014 Last lumbar, length of centrum .016 " " width of posterior face .013 Sacrum, width overpleurapophyses .036 Scapula, length .056 " width .03 5 Ilium, greatest width .018 GLIRES OF THE SANTA CRUZ BEDS. 485 The measurements of limb-bones are all from No. 15,648. Humerus, length 062 Tibia, distal width oio " proximal width on Fibula, distal width 004 " distal width 01 2 " " thickness 006 " width of trochlea OOQS Astragalus, length 013 Radius, proximal width 007 " width of trochlea 007 Ulna, width at sigmoid notch 0065 " " " distal end 006 Femur, length from head 080 Metatarsal II, length 030 " " " great trochanter .. .084 " " proximal width 004 " proximal width 02 1 " " distal 005 " distal width 017 Metatarsal III, length 03 1 Tibia, length 091 " " proximal width 0055 " proximal width 0175 " " distal width 007 SCHISTOMYS ROLLINSII Sp. HOV. (Plate LXIX, Figs. 1 8-1 8s.) The type specimen (No. 15,969), an incomplete skull, was found by Mr. Hatcher at Lake Pueyrredon. In size, this species equals S. ellipticus, but differs in many other respects. The upper incisors which are dis- played in the broken end of the rostrum, are remarkably thick; p1, though entirely molariform, is very small and m^ has a shorter posterior process than in the preceding species ; the downward inclination of the grinding surfaces of the upper dental series is less marked, the face being less flexed upon the cranial axis ; the cranium is more depressed and flat- tened, with less antero-posterior arching ; the supraorbital border is some- what raised and thickened, but not notched. The rostrum is long and exceedingly broad, especially on the dorsal side, narrowing on the ventral side, and the nasals are much wider than in S. ellipticus. The palate is slightly less triangular than in the latter and the posterior nares are not so broad and have more nearly parallel sides, being shaped more as in Rocardia. MEASUREMENTS. Upper dentition, length pA-mS. 017 M-2-, length 0055 Upper incisor, width 003 Skull, interorbital width 024 " " thickness 0045 Palate, width at p± 004 PA, length (i. e., antero-posterior diam- " " " m^ OIO eter) 0025 Rostrum, width at base 015 " width (i. e., transverse diameter). . . .003 This species is dedicated to my friend, Philip Asheton Rollins, Esq., of New York, whose interest in the work of Patagonian exploration has been repeatedly and most generously displayed. 486 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. SCHISTOMYS ERRO Ameghino. (Plate LXVIII, Figs. 26-26".) Schistomys erro Amegh. ; Enumeracion sistem., etc., 1887, p. 13. This species, though the type of the genus, is much less common and less well known than S. ellipticus, from which it is distinguished by its very much smaller size. So far, no transitional forms, tending to connect the two species, have been found and there can be little doubt that the separation is justified. In the Princeton collection S. erro is represented by the crushed skull of a young individual, with the milk premolars in place and m^ just erupt- ing, but still entirely unworn. The specimen is too badly damaged for any instructive comparison with the skull of 5. ellipticus, except to note its greater relative breadth and the less triangular palate. Associated with the skull are the distal end of the tibia, the astragalus and calcaneum ; these bones differ only in size from those of S. ellipticus. MEASUREMENTS. Upper dentition, length dp±-mi 013 Palate, width at nr§- oio DpA, length (i. e., antero-posterior diam- Tibia, distal width 006 eter) 0025 " " thickness 006 Dpi, width (j. e., transverse diameter) .0025 Astragalus, length 009 Skull, interorbital width. 018 " width of trochlea 005 Palate, width at dp± 006 PHANOMYS Ameghino. Phanomys Amegh. ; Enumeracion sistem., etc., 1887, p. 13. This interesting genus is unfortunately known only from a few grind- ing teeth, which, though hypsodont, are conical and closed at the base, where the valley between the two prisms becomes very shallow and dies away. Evidently, Phanomys indicates the transition between the cavies of the Patagonian beds, with rooted molars, and the typical Santa Cruz forms with rootless teeth, open at the base. The two species named differ only in size. PHANOMYS MIXTUS Ameghino. Phanomys mixtus Amegh.; Enumeracion sistem. etc., 1887, p. 13. Larger, the upper teeth measuring each 3-4 by 2-3 mm. GLIRES OF THE SANTA CRUZ BEDS. 487 4 PHANOMYS VETULUS Ameghino. Phanomys vetulus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 146. Smaller, upper teeth measuring 2.5 mm., each in antero-posterior diameter. GENUS INCERT^E SEDIS. CALLODONTOMYS Ameghino. Callodontomys Amegh. ; Contrib. al Conoc. de los Mam. Fos. de la Repub. Argent, 1889, p. 259; PI. IX, figs. 27, 27". This supposed genus is known only from the incisor, which is char- acterized by a deep groove on the posterior face and is not improbably pathological. The species assigned is CALLODONTOMYS VASTATUS Ameghino. Callodontomys vastatus Amegh. ; Loc. cit. BIBLIOGRAPHY. Ameghino, Florentine. 1887" Observaciones generales sobre el orden de mamiferos estinguidos sud-americanos llamados Toxodontes (Toxodontia) y sinopsis de los generos y especies hasta abora conocidos. La Plata, 1887. 1887* Enumeracion sistematica de las especies de mamiferos fosiles coleccionados por Carlos Ameghino en los terrenes eocenos de la Patagonia austral. La Plata, 1887. 1889* Contribucion al conocimicnto de los mamiferos fosiles de la Republica Argentina (Actas de la Academia Nacional de Ciencias de Cordoba, T. V). 1891° Las antiguas conexiones del continente Sud Americano y la fauna eocena argentina (Revista Argentina de Historia Natural, T. I, p. 123). 1891* Caracteres diagnosticos de cincuenta especies nuevas de mamiferos fosiles argentinos (Ibid., p. 129). l8gid Mamiferos y aves fosiles argentinas — Especies nuevas, adiciones y correcciones (Ibid., p. 240). 1891" Nuevos restos de mamiferos fosiles descubiertos por Carlos Ameghino en el eoceno inferior de la Patagonia austral. — Especies nuevas, adiciones y correcciones (Ibid., p. 289). 1891* Observaciones criticas sobre los mamiferos eocenos de la Patagonia austral (Ibid., p. 328). 1893^ Nouvelles decouvertes paleontologiques dans la Patagonie australe (Revue Scientifique, T.LI, p. 13). PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 1894° Enumeration synoptique des especes de mammiferes fossiles des formations eocenes de Patagonie (Boletin de la Academia Nacional de Ciencias en Cordoba, T. XIII, p. 259). In the citations from this paper given in the text the paging is that of the, separate edition. 1898 Sinopsis geologico-paleontologica (Segundo Censo de la Republica Argentina, T. I. Buenos Aires, 1898, p. 113). 1902 Notices preliminaires sur des mammiferes nouveaux des terrains cretaces de Patagonie (Bol. de la Acad. Nac. de Cien. en Cordoba, T. XVII, p. i). Brown, Barnum. 1903 A new species of fossil edentate from the Santa Cruz formation of Patagonia (Bulletin of the American Museum of Natural History, New York, Vol. XIX, p. 453). Burmeister, Hermann. 1870-74 Monografia de los Glyptodont£S en el Museo Publico de Buenos Aires (Anales del Museo Publico de Buenos Aires, T. II, p. i). Dobson, G. £. 1882-90 Monograph of the Insectivora, systematic and anatomical. London, 1882-1890. Flower, W. H. 1882 On the mutual affinities of the animals composing the order Edentata (Proceedings of the Zoological Society of London, 1882, p. 358). Huxley, T. H. 1865 Osteology of the genus Glyptodon (Philosophical Transactions, Vol. 155, p. 31). Leidy, Joseph. 1855 A memoir on the extinct sloth tribe of North America (Smithsonian Contributions to Knowledge, 1853). i860 Remarks on the structure of the feet of Megalonyx (Transactions of the American Philosophical Society, Vol. XI, p. 107). Lindahl, Josua. 1891 Description of a skull of Megalonyx Leidyi (Ibid., Vol. XVII, p. i). Lydekker, Richard. 1894 The extinct edentates of Argentina (Anales del Museo de La Plata, T. Ill, pt. II, p.i). 1896 A geographical history of mammals. Cambridge, 1 896. Mercerat, Alcides. iSgi*7 Datos sobre restos de mamiferos fosiles pertenecientes a los Bruta, conservados en el Museo de la Plata y precedentes de los terrenes eocenos de Patagonia (Revista del Museo de La Plata, T. II, p. 5). Moreno, F. P. 1882 Patagonia, resto de un antiguo continente hoy sumerjido (Conferencias de la Sociedad Cientifica Argentina, Conferencia del 15 del Junio de 1882). Moreno, F. P., & Mercerat, A. 1891 Nota sobre algunas especies de un genero aberrante de los Dasypoda (Revista del Museo de La Plata, T. II, p. 57). GLIRES OF THE SANTA CRUZ BEDS. 489 Osborn, H. F. 1903 Glyptothcrium texanum, a new Glyptodont from the lower Pleistocene of Texas (Bulletin of the American Museum of Natural History, New York, Vol. XIX, p. 491). 1904 An armadillo from the Middle Eocene of North America (Ibid., Vol. XX, p. 163). Owen, Richard. 1842 Description of the skeleton of an extinct gigantic sloth, Mylodon robustus. London, 1842. 1855 On the Megatherium. — Part II. — Vertebrae of the trunk (Philosophical Transactions, Vol. 145, p. 359). 1856 The same. — Part III. — The skull (Ibid., Vol. 146, p. 571). 1857 On the Scelidothere (Ibid., Vol. 147, p. 101). 1858 On the Megatherium. — Part IV. — Bones of the anterior extremities (Ibid., Vol. 148, p. 261). 1859 The same. — Part V. — Bones of the posterior extremities (Ibid., Vol. 149, p. 809). Reinhardt, J. 1878 Om Kjaempendovendyret Ccelodon (Vidensk. Selsk. Skr., 5 Raekhe, naturwidenskabelig og mathematisk Afd. XII. Copenhagen). 1879 Beskriv. of Hovedskallen of Grypotherium Darwini (Ibid.). Thomas, Oldfield. 1887 On the homologies and succession of the teeth in the Dasyuridae, with an attempt to trace the history of the mammalian teeth in general (Philosophical Transactions, Vol. 178*, p. 443)- 1896 On the genera of Rodents, an attempt to bring up to date the current arrangement of the order (Proceedings of the Zoological Society of London, 1896, p. 1012). Tornouer, A. 1903 Note sur la geologic et la paleontologie de la Patagonie (Bulletin de la Societe geo- logique de France, 4" serie, T. Ill, p. 463). / Tullberg, Tycho. ' 1899 Ueber das System der Nagethiere, eine phylogenetische Studie. Upsala, 1899. Winge, H. 1887 Jordfunde og nulevende Gnavere (Rodentia) fra Lagoa Santa, Minas Geraes, Brasilien. Med over Gnavernes inbyrdes Slaegtskab. (E. Museo Lundi, III). Wortman, J. L. 1896 Psittacotherium, a member of a new and primitive sub-order of the Edentata (Bulletin of the American Museum of Natural History, New York, Vol. VIII, p. 259). 1897 The Ganodonta and their relationship to the Edentata (Ibid., Vol. IX, p. 59). 490 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. ERRATA. Page 10. Explanation of Fig. $d; for right ramus read left ramus. Page 104. For ? PELTEPHILUS RARUS Ameghino, read ? P. RARUS (Amegh.). Page 1 1 4. For Fig. 3 read Fig. 1 3. Page 1 54, line 9 (from bottom); for Propalaohaplophorus read Propalczohoplophorus. Page 1 63. Explanation of Fig. i $g ; for Nematherium sp. read N. angulatum. Page 167. " " " iqg; " " " " " " . Page 167. " " " i ge ; for Schismotherium splendens read S. fractum. Page 173. Explanation of Fig. 256; for Analcimorphus leptocephalus read A. giganteus. Page 174. Explanation of Fig. 26^; for Analcimorphus leptocephalus read A. giganteus. Page 213, line 13; for Encholceops read Eucholceops. Page 238. For HAPALOPS INFERNALIS Ameghino, read H. INFERNALIS (Amegh.). Page 239. For HAPALOPS ROSTRATUS Ameghino, read H. ROSTRATUS (Amegh.). Page 241. For HAPALOPS ATLANTICUS Ameghino, read H. ATLANTICUS (Amegh.). Page 241. For HAPALOPS RECTANGULIDENS Ameghino, read H. RECTANG. (Amegh.). Page 242. For HAPALOPS CONGERMANUS Ameghino, readH. CONGERMANUS (Amegh.). Page 243. For HAPALOPS RUETIMEYERI Ameghino, read H. RUETIMEYERI (Amegh.). Page 251. For HAPALOPS FORTICULUS Ameghino, read H. FORTICULUS (Amegh.). Page 252. For HAPALOPS GRANDIS Ameghino, read H. GRANDIS (Amegh.). Page 252. For HAPALOPS LONGITUDINALIS Ameghino, read H. LONGIT. (Amegh.). Plate VI, Explanation of Fig. 26; for No. 15,563 read No. 15,863. Plate VIII, Explanation; for No. 15,597 read No. 15,957. Plate XII, Explanation of Fig. 9; add (No. 15,433). Plate XLVII, Explanation ; for Analcimorphus gigas read A. giganleus. Plate XLVIII, " " " " " " Plate XLIX, " " " " " " PATAGONIAN EXPEDITIONS VOLV PLATE i. * coiofi oo., ». r. STEGOTHERIUM PATAGONIAN EXPEDITIONS! PALEONTOLOGY. EXPLANATION OF PLATE II. PAGE STEGOTHERIUM TESSELATUM : Restoration of skeleton, X yz . . . . 35 The skull, neck, 2 thoracic vertebrae and the pes are from one indi- vidual (No. 15,565) and the remainder of the skeleton from a second (No. 15.566). (VOL. v) PATAGONIAN EXPEDIT] PLATE n. F. v. irerson del. Werner I Winter, frankfort?M., tirh PATAGONIAN EXPEDITIONS I PALEONTOLOGY. EXPLANATION OF PLATE III. PAGE Fig. i. STEGOTHERIUM TESSELATUM : Skull, top view (No. 15,565) ... 14 Fig. 2. " Occiput (No. 15,565). Fig. 3. Skull, base (No. 15,565). Fig. 4. " " " side view (No. 15,565). Fig. 5. " " . Skull, side view (No. 15,566). Fig. 6. " base (No. 15,566). All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE in F. v. Iterson del Werner i Winter, Frankfort'.M . lirh STEGOTHERIUM PATAGONIAN EXPEDITIONS I PALEONTOLOGY. EXPLANATION OF PLATE IV. PAGE Fig. i. STEGOTHERIUM TESSELATUM : Cervical vertebrae, ventral side (No. 15.565) • .22 Fig 2. " " First, seventh and tenth caudal verte- brae, dorsal side (No. 15,566) . . 27 Fig. 3. " " Left scapula (No. 15,566) ... 28 Fig. 4. " " Left humerus, from the front (No. 15.566) . 29 Fig. 5. " " Left femur, from the front (No. 15-566) . 31 Fig. 6. " " Left tibia and fibula, front view (No. 15,566) . . 32 Fig. 7. " Right pes, dorsal side (No. 15,565) . 33 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE iv. 6 F. v. Uerson del. Werner i Winter, rrankfort^M.. lirh STEGOTHERIUM FATAGONIAN EXPEDITIONS: PALEONTOLOGY. EXPLANATION OF PLATE V. PAGE PROZAEDIUS PROXIMUS. Carapace; natural size (No. 15,237) ... 78 (VOL. v; PATAGONIAN EXPEDITIONS VOLV. PLATE v. . COiOR CO.. rt V. PROZAEDIUS PATAGONIAN EXPEDITIONS! PALEONTOLOGY. EXPLANATION OF PLATE VI. PAGE Fig. i. PROZAEDIUSEXILIS: Skull, right side (No. 15,579) . 7° Fig. 2. " top (No. 15,579)- Fig. 3. " " base (No. 15,579)- Fig. 4. Occiput (No. 15,579). Fig. 5. Left scapula (No. 15,579) 74 Fig. 6. " Right humerus, front view (No. 15,579) • • 74 Fig. 7. " " Right ulna, external side (No. 15,579) • • 74 Fig. 8. " " Right radius, front view (No. 15,579) . 74 Fig. 9. " " Right manus, lacking digit V (No. 15,579) . 74 Fig. 10. " " Lumbar vertebree and pelvis, ventral side (No. 15.579) 73 Fig. ii. " " Right femur, front view (No. 15,579) . . 75 Fig. 12. " " Right tibia and fibula, front view (No. 15,579) • 75 Fig. 13. " " Scutes of carapace, movable bands (No. 15,579) 77 Fig. 14. " " " " " pelvic shield (No. 15,579) . 77 Fig. 15. PROZAEDIUS PROXIMUS : Skull, left side (No. 15,567) ... 70 Fig. 16. " " " ' top (No. 15,567). Fig. 17. " " " base (No. 15,567). Fig. 18. " " Left pes, dorsum (No. 15,567) ... 76 Fig. 19. STENOTATUS PATAGONICUS : Part of cephalic shield (No. 15,863) . 80 Fig. 20. " " Skull, right side (No. 15,863) . . 81 Fig. 21. Right humerus, front (No. 15,863) . 83 Fig. 22. Right ulna, outer side (No. 15,863) . 83 Fig. 23. " " Right radius, front (No. 15,863) . . 83 Fig. 24. " " Right manus, pisiform detached (No. i5,863) 83 Fig. 25. Lumbar vertebrae and pelvis (No. 15,563), ventral side ..... 82 Fig. 26. " " Left femur, proximal end (No. 15,563) . 85 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOLV. PLATE vi. 15 20 F. v. Irerson del w'erne r t Winter. Frankforr?M., lith PROZAEDIUS & PRODASYPUS PATAGONIAN EXPEDITIONS! PAL/EONTOLOGY. EXPLANATION OF PLATE VII. PAGE Fig. i. STENOTATUS PATAGONICUS : Anterior part of carapace (No. 15,863) . 80 Fig. 2. " " Posterior part of carapace (No. 15,563) . 80 Fig. 3. STENOTATUS HESTERNUS : Fragment of carapace : Ameghino collection . 87 Fig. 4. PROEUTATUS CARINATUS : Fragment of pelvic shield : Ameghino collec- tion ............ 67 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOLV. PLATE YII. PMOTOQRAVUftt A COLOft CO., W, Y STENOTATUS & PROEUTATUS PATAGONIAN EXPEDITIONS: PALEONTOLOGY. EXPLANATION OF PLATE VIII. PAGE PROEUTATUS ROBUSTUS ? carapace (No. 15,597) 43 Slightly less than three fourths natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOLV. PLATE YIII. PROEUTATUS PHOTOONAVUftf * OOLOft CO., N. Y. PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. EXPLANATION OF PLATE IX. p 42 PROEUTATUS ROBUSTUS, type: Dorsal view (No. 15,214) Natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL v. "V, PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. EXPLANATION OF PLATE X. PAGE PROEUTATUS ROBUSTUS, type : Ventral view (No. 15,214). . . . . 49 Natural size. (VOL. v) PATAGONIAI PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. EXPLANATION OF PLATE XI. PAGE PROEUTATUS ROBUSTUS : Restoration of skeleton ; one half natural size . . 57 The drawing is made from the type-specimen, except the hind-limb, which is restored from other specimens agreeing with the type in size, while the pelvis is from another individual doubtfully referable to this species, and the caudal verte- brae are enlarged from those of P. lagena. (VOL. v) PATAGONIAN EXPEDITIONS Vc PLATE xi. F. v. Irerson del Werner i Winter.frankfort'/M., lirh. PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. EXPLANATION OF PLATE XII. PAGE Fig. i. PROEUTATUS CENOPHORUS : Skull, left side (No. 15,491) ... 59 Fig. 2. base (No. 15,491). Fig. 3- top (No. 15,491). Fig. 4. " Occiput (No. 15,491). Fig. 5. " " Mandible, crown view (No. 15,491). Fig. 6. " " Rostrum, ventral side (No. 15,491). Fig. 7. PROEUTATUS sp. : Skull, top (No. 15,433). Fig. 8. " base (No. 15,433)- Fig. 9. " " Occiput. Fig. 10. PROEUTATUS DELEO, type : Scute of carapace ; Ameghino collection . 67 Ki,, IT " " " " " " " " Fig. 12. " Mandible, right side All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE MI. F v. Irerson del. Werner « Wmfer. FrankforttM., lirh. PROEUTATUS PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. EXPLANATION OF PLATE XIII. PAGE Fig. i. PROEUTATUS LAGENA : Skull, left side (No. 15,613) .... 65 Fig. 2. " " " base (No. 15,613). Fig. 3. " top (No. 15,613). Fig. 4. PROEUTATUS ROBUSTUS, type : Skull, right side (No. 15,214) . . 43 Fig. 5. " base (No. 15,214). Fig. 6. PROEUTATUS sp. Occiput. Fig. 7. PROEUTATUS LAGENA : Caudal vertebrae (No. 15,958) ... 66 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE xin. F. v. Irerson del Werner I Winter, Frankfort?M., lirn. PROEUTATUS PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. EXPLANATION OF PLATE XIV. PAGE Fig. i. PROEUTATUS ROBUSTUS, type: Left humerus, front (No. 15,214) . . 51 Fig. 2. " " " Right radius, front (No. 15,214) . . 51 Fig. 3. " " " Right ulna, outer side (No. 15,214) . 51 Fig. 4. " " " Right manus, dorsum (No. 15,214) . 51 Fig. 5. PROEUTATUS CENOPHORUS : Right manus, dorsum (No. 15,491) . . 60 Fig. 6. " " Right pes, dorsum (No. 15,491) . . 62 Fig. 7. PROEUTATUS LAGENA : Left pes, dorsum (No. 15,553) ... 66 Fig. 8. PROEUTATUS sp. : Right pes, showing sesamoid on tibial side (No. 15,869) ... 62 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE xiv. F. v. Irerson del Werner I Winter. Frankfort^M., lirh. PROEUTATUS PATAGONIAN EXPEDITIONS! PALEONTOLOGY. EXPLANATION OF PLATE XV. PAGE Fig. i. PROEUTATUS ROBUSTUS ? : Pelvis, leftside 55 Fig. 2. " " " rear end. Fig. 3. PROEUTATUS ROBUSTUS : Left femur, front (No. 15,389) ... 56 Fig. 4. " Left tibia and fibula, front (No. 15,389) . 57 Fig. 5. " " Left calcaneum, dorsal side (No. 15,389). Fig. 6. " " Left astragalus, dorsal side (No. 15,389) . 57 Fig. 7. PROEUTATUS LAGENA : Right femur, lacking great trochanter (No. 15,553) 66 Fig. 8. " " Left tibia and fibula, front (No. 15,553) . . 66 All figures natural size. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE xv. F. v. Irerson del. Werner 4 Winter. Frankfort 'IM., lirh. PROEUTATUS PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. EXPLANATION OF PLATE XVI. Fig. i. PEI.TEPHILUS FEROX: Skull, right side. Ameghino collection. (The suture between the zygyomatic process and the squamosal has been inadvertently omitted in this figure.) ...... Fig. 2. PELTEPHILUS FEROX: Skull, top. Ameghino collection Fig. 3. PELTEPHILUS PUMILUS : Skull, right side (No. 15,391) Fig. 4. " " " base (No. 15,391). Fig. 5. " top (No. 15,391). Fig. 6. PELTEPHILUS GRANDIS : Median posterior plate of head-shield. Ame- ghino collection ...... Fig. 7. PELTEPHILUS STREPENS : Part of head-shield (No. 15,390) Fig. 8. " " Scutes of carapace (No. 15,390) Fig. 9. " " Right ulna, lacking proximal epiphysis (No. 15.390). Fig. 10. " " Right radius, front (No. 15,390) Fig. ii. " " Right manus, lacking digit V (No. 15,390) Fig. 12. " " Right femur, front (No. 15,390) Fig. 13. " Right tibia and fibula, front (No. 15,390) . Fig. 14. " " Left pes, dorsum (No. 15,390) . All figures natural size. PAGE 88 88 101 103 99 89 94 95 95 96 96 97 (VOL. v) PATAGONIAN EXPEDITIONS VOL g F. v. Irerson del. PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. EXPLANATION OF PLATE XVII. PAGE PROPAL^EOHOPLOPHORUS MINOR : Left side of carapace, X y2 . American Museum of Natural History (No. 9, 197) 116, 138 The large area above the movable bands and the posterior 'border above the fifth pointed marginal scute are restored, as may be seen from an exami nation of the surface texture. (VOL. v) PATAGONIAN EXPEDITIONS : PALEONTOLOGY EXPLANATION OF PLATE XVIII. PAGE Fig. i . PROPAL^OHOPLOPHORUS AUSTRALIS : Right side of carapace, X */£ (No. 15,212) 1 16 Fig. 2. PROPAL/EOHOPLOPHORUS AUSTRALIS : Tip of tail-sheath, natural size (La Plata Museum). 117 Fig. 3. PROPALyEOHOPLOPHORUS AUSTRALIS : Fragment of tail-sheath, natural size (La Plata Museum). (VOL. v) PATAGONIAN EXPEDITIONS VOLV. PLATE xvm. PHOTOGRAVURE A COLOR co , N. v. PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. EXPLANATION OF PLATE XIX. PAGE Fig. i. COCHLOPS MURICATUS : Right side of carapace, X yz (No. 16,000) . .141 Fig. 2. " " Tail-sheath, lacking first ring, X ^ (Ameghino collection) . . . . .142 Fig. 3. COCHLOPS MURICATUS : Tuberculated plate from pelvic region of carapace seen from the side, natural size (Ameghino collection) . . .142 (VOL. v) PATAGONIA* PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. EXPLANATION OF PLATE XX. PAGE COCHLOPS MURICATUS : Fragment of carapace, X y2 (No. 15,867). The specimen is seen from above and shows the median dorsal band and part of the left pelvic area of modified plates ; the anterior part of the carapace is toward the top of the plate . . . . . . . .142 (VOL. v) PATAGONIAN EXPEDITIONS VOLV. PLATE xx PHOTOGRAVURE * COLOR cc., M. v. COCHLOPS PATAGONIAN EXPEDITIONS : PALEONTOLOGY. EXPLANATION OF PLATE XXI. PAGE Fig. i. PROPAL/EOHOPLOPHORUS AUSTRALIS : Portion of cephalic shield (No. 15,212). The anterior end of the shield is to the left. . . .115 Fig. 2. EUCINEPELTUS CRASSUS, type : Cephalic shield (No. 15,865) . . .152 Fig. 3. EUCINEPELTUS COMPLICATES, type : Cephalic shield : Amer. Mus. Nat. Hist. (No. 9,248) 151 Fig. 4. EUCINEPELTUS PETESTATUS, type: Cephalic shield (Ameghino collection). 149 Fig. 5. COCHLOPS DEBILIS : Cephalic shield in place (No. 15,592); the rostrum has been cut off short to gain space . . . . . . . 1 40 Fig. 6. ? ASTEROSTEMMA DEPRESSA : Tail-sheath, X ^ (No. 16,001) . . . 154 All figures, except fig. 6 natural size. (VOL. v) PATAGONIAN EXPEDIT PLATE y PHOTOGRAVURE A COLOR CO., N. V. PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. EXPLANATION OF PLATE XXII. PAGE i .TlVJij PROPAL/EOHOPLOPHORUS AUSTRALIS : Restoration of skeleton, x % . . -134 This figure has been made chiefly from the skeleton in the La Plata Museum, with the addition of some details from material in the Princeton and New York collections. (VOL. v) PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. EXPLANATION OF PLATE XXIII. PAGE Fig. i. PROPALJEOHOPLOPHORUS AUSTRALis : Skull, leftside . . . . .119 Fig. 2. " " " dorsal view . . . . 135 Fig. 3. " " " ventral view. Fig. 4. " " " from the front. Fig. 5. " " " from the rear. All the figures are ^ natural size and from the same individual (No. 15,212). (VOL.. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE xxm. F.v. Iterson del. Wernsr S Winter, Frankfort?M.. lirh. PROPAL^OHOPLOPHORUS PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. EXPLANATION OF PLATE XXIV. PAGE Fig. i. PROPAL^OHOPLOPHORUS AUSTRALIS : Upper dentition (No. 15,212) . 118 Fig. 2. " " " " (No. 15,007) . 135 Fig. 3. " " " " (La Plata Museum). Fig. 4. " " " " (Ameghino collection). P- _ (( It it it . NEOREOMYS AUSTRALIS: Skull, base, x f. No. 15,572. Palate and teeth injured. Fig. 6c. NEOREOMYS AUSTRALIS: Occiput, X \. No. 15,572 . . . 392 (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE LXIV. -P.oe F. v. Iterson del. Werner 4 Wmisr, frankfor;' NECROLESTES & NEOREOMYS PATAGONIAN EXPEDITIONS: PALEONTOLOGY. EXPLANATION OF PLATE LXV. PXGB Fig. i. NEOREOMYS AUSTRALIS, juv.: Skull, base, X ^. No. 15,222. . 389 Fig. 2. " " Palate and upper teeth, X \ . No. 15,302. Pal., palatines. Fig. 3. ? NEOREOMYS AUSTRALIS : Right upper milk-premolar (dp-), X \. No. 15,936 390 Fig. 4. NEOREOMYS AUSTRALIS, juv.: Right upper teeth, X \. A. M. N. H. No. 9,168 . . 389 Fig. 5. NEOREOMYS AUSTRALIS : Left upper teeth, X y. No. 15,813. Fig. 6. NEOREOMYS AUSTRALIS, juv.: Left lower teeth, X T. A. M. N. H. No. 9,540 . 390 Fig. 7. NEOREOMYS AUSTRALIS, juv.: Left lower teeth, X T. No. 15,619. Fig. 8. " " Left lower teeth, X i No. 15,499. Fig. 9. " " Left lower teeth, X T. A. M. N. H. No. 9.58o. Fig. 10. NEOREOMYS AUSTRALIS : Left lower teeth, X T. No. 15,394. Fig. ii. " " Mandible, crown view, X T. No. 15,226. 394 Fig. 12. NEOREOMYS VARIEGATUS, type: Left lower teeth, crown view; X T. Ameghino collection . . . . . . . 401 Fig. 13. SCLEROMYS ANGUSTUS : Palate and upper teeth, X T. A. M. N. H. No. 9,304 402 Fig. 14. SCLEROMYS ANGUSTUS : Left lower teeth, crown view, X T. Ame- ghino collection. Fig. 15. SCLEROMYS OSBORNIANUS: Left lower teeth, crown view, X T. Ameghino collection ........ 402 Fig. 16. STICHOMYS REGIUS: Skull, top, XT. A. M. N. H. No. 9,495 . 405 Fig. 17. STICHOMYS REGULARIS : Palate and upper teeth, X f. A. M. N. H. No. 9,512 . . . . • . . . . . . 406 Fig. 1 8. STICHOMYS REGIUS : Fragment of left ramus mandibuli, with pT and m^, X f . A. M. N. H. No. 9,495 407 Fig. 19. STICHOMYS REGULARIS: Right upper teeth, crown view, Xf. No. 15.555 • • 406 Fig. 20. STICHOMYS REGULARIS : Left ramus mandibuli, side view, X T. No. 15,423 ... 407 Fig. 200. STICHOMYS REGULARIS : Left lower teeth, crown view, X f . No. 15.423- Fig. 2 1 . ADELPHOMYS CANDIDUS : Right lower teeth, crown view, X f. Ameghino collection ........ 408 Fig. 22. SPANIOMYS RIPARIUS : Skull, right side, X T. A. M. N. H.No. 9,529. 410 PATAGONIAN EXPEDITIONS VOL.V. PLATE LXV. 24 26 27 ">on dei. Wernsr 4 Winter. Frankforr?M.. lith. SANTA CRUZ OCTODONTJD/E PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. PAGE Fig. 22a. SPANIOMYS RIPARIUS : Left upper teeth, X f. A. M. N. H.No. 9,529. 410 Fig. 23. " " Left lower teeth, X f. No. 15,577 . . 411 Fig. 24. SPANIOMYS BIPLICATUS, type : Right lower teeth, X f. Amegh. coll. 412 Fig. 25. GYRIGNOPHUS COMPLICATES, type : Right lower teeth, X ^. Amegh. coll. ........... 409 Fig. 26. GRAPHIMY^ PROVECTUS, type : Left lower teeth, X f. Amegh. coll. 413 Fig. 27. LOMOMYS INSULATUS: Right upper teeth, X f . Amegh. coll. . 403 (VOL. v) PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. EXPLANATION OF PLATE LXVI. PAGE Fig. i . STEIROMYS DUPLICATUS : Skull, seen obliquely from above, X y. Ameghino collection . . . . . . . . 414 Fig. 2. STEIROMYS DUPLICATUS : Left ramus mandibuli, side view, X -^. No. 15,868 419 Fig. 2a. STEIROMYS DUPLICATUS : Left ramus mandibuli, crown view, X •£. No. 15,868. Fig- 3- STEIROMYS INTERMEDIUS ? : Right upper teeth, slightly less than natural size. Ameghino collection . . . . . . 418 Fig. 4. STEIROMYS INTERMEDIUS, type : Right ramus mandibuli, X ^. No. 15,367 418 Fig. 40. STEIROMYS INTERMEDIUS, type : Right lower teeth, crown view, X y. No. 15,367. Fig. 5. STEIROMYS DUPLICATUS : Left ramus mandibuli, side view, X T. Ameghino collection. Fig. 6. STEIROMYS DETENTUS : Palate and upper teeth, X T. A. M. N. H. No. 9,555 414 Fig. 7. STEIROMYS DETENTUS : Right ramus mandibuli, X T.- No. 15,094. 418 Fig. 7«. " " Right lower teeth, crown view, X T. No. 15,094 . 418 Fig. 8. STEIROMYS DUPLICATUS : Part of left manus, dorsal view, X T. No. I5.J56 ... 415 Fig. 9. STEIROMYS DUPLICATUS: Left pes, dorsal view, X •£. No. 15,156. En., Entocuneiform ; S., first tibial sesamoid ; S.', second tibial sesamoid. .......... 416 Fig. 10. SCIAMYS PRINCIPALIS: Skull, right side, X f . No. 15,623. The alveolus of the upper incisor is too prominent and in this figure and the following one the lachrymal suture has been over- looked . .......... 425 Fig. loa. SCIAMYS PRINCIPALIS: Skull, top, x f • No. 15,623. Fig. \ob. " " Skull, base, X f. No. 15,623. Fig. ii. ACAREMYS MURINUS: Skull, top, Xf. A. M. N. H. No. 9,280. 430 Fig. na. " Skull, base, X f . A. M. N. H. No. 9,280. (VOL. v) PATAGONIAN EXPEDITIONS VOL.V. PLATE LXVI. 10b v J F. v. Irerson del. Werner ( Winrer. Frankforr?M., lirh. SANTA CRUZ ERETHIZONTID^E PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. EXPLANATION OF PLATE LXVII. PACK Fig. i. SCIAMYS LATIDENS, type : Skull, top, X f No. 15,944. 421 Fig. la. " " " Skull, base, X A. No. 15,944, Fig. \b. " " " Skull, left side, X f No. 15,944. Fig. ic. " " " Left upper teeth, X f. No. 15,944 . 428 Fig. id. " " " Left lower teeth, Xf. No. 15,944 . 428 Fig. \e. " " " Skull, left side, Xf No. 15,944. The ventral border of the mandible has an unduly strong curvature, due to the even fracture and loss of the incisor sheath. Fig. if. SCIAMYS LATIDENS, type: Skull, base, Xf. No. 15,944 . . 421 Fig. ig. " " " Skull, top, Xf No. 15,944. Fig. 2. " " " Right tibia and fibula, X f No. 15,944 424 Fig. 3. " " " Right pes, dorsum, X f No. 15,944 . 424 Fig. 4. ACAREMYS MURINUS: Skull, top, Xf A. M. N. H. No. 9,280 . 430 Fig. 4«. " " Skull, base, Xf A. M. N. H. No. 9,280. Fig. 46. " " Skull, side, X f A. M. N. H. No. 9,280. Fig. 5. SCIAMYS VARIANS : Skull, top, X f No. 15,575 .... 426 Fig. 5«. " " Skull, base, X A. No. 15,575. Fig. $l>. " " Skull, side, Xf No. 15,575!. Fig. 6. SCIAMYS ROSTRATUS, type : Skull, top, Xf No. 15,287 . . 427 Fig. 6a. " " " Skull, base, Xf No. 15,287. Fig. 6b. " " " Skull, side, X f No. 15,287. Fig. 7. SCIAMYS PRINCIPALIS: Skull, top, Xf No. 15,623 . . . 425 Fig. 70. " " Skull, base, X f No. 15,623. Fig. 7<$. " " Skull, side, Xf No. 15,623. Fig. TC. " " Right upper teeth, X f No. 15,623 . . 425 Fig. yd. " " Right lower teeth, X f No. 15,623. Fig. 8. SCIAMYS sp. : Left lower teeth, crown view, X f. No. 15,283 . 421 Fig. 9. SCIAMYS VARIANS : Auditory region of skull, left side, X f No. 15,168. S.s.m., supramastoid process of squamosal ; Ty., tym- panic ; Per., periotic; P.oc., paroccipital process ; P.M., foramen magnum ........... 42 1 Fig. 10. ACAREMYS MINUTUS : Skull, top, X f No. 15,806 . . . 432 Fig. 100. " " Skull, base, Xf No. 15,806. Fig. io<5. " " Skull, side, X f No. 15,806. Fig. io8 421, 422, 423, 424, 425 dorsatum, 419, 420 Erethizontidae, 385, 387, 388, 413 Erethizontinae, 385, 413, 421, 422 Eucholceops, 163, 177, 213, 214, 262, 263, 265, 278 curtus, 266, 276, *2/7 externus, 266, 269, 270, 272 fronto, *i63, *i6s, *i66, *i67, 266, ingens, 266, 267, 269, 272 lafonei, 269 latifrons, 269 latirostris, 267 Eucholceops, 179, 261, 328 adteger, 258 fissognathus, 262 infer nalis, 238, 328 ingens, 206, 208, 213 litoralis, 262 titan, 266, 332 Eucinepeltus, 107, 109, no, in, 115, 116, complicatus, *uo, *iu, 148, H9. '5°, 153 crassus, 148, 149, 152 petestatus, "109, *iio, 148, 149, 151 Eugeronops, 179 circularis, 243 Euphractus, 69, 80 exilis, 76 patagonicus, 86 proximus, 78 Europe, 381 Eurysodon, 180 adteger, 258 boulei, 260 nasutus, 217 rostratus, 260 Eutatus, 41, 42 Eutatus, 40 bipunttatus, 58 carinatus, 67 l patagonensis, *376, Necrolestidae, 365 Nematherium, 178, 346, 357, 358 angulatum, *i63, *i6y, *I 355, 357 auca, 353 declivum, 356 lavagnanum, 352, 353 longirostris, 347, 352 profundatum, 354 sinuaium, 352 sp., *35o Neoreomys, 385, 387, J