HARVARD UNIVERSITY VEEL Lash LIBRARY OF THE Museum of Comparative Zoology 1 iy) Bike ty ay: why at LA oT r Ae oe. Py f r " iy 5 Wi aman ‘ ") JUN10 1936 THE PEABODY MUSEUM OF NATURAL HISTORY BULLETIN 4 16,567 MIOCENE MARINE MAMMALS FROM THE BAKERSFIELD REGION, CALIFORNIA BY LESLIE E. WILSON PRICE $1.25 NEW HAVEN THE PEABODY MUSEUM OF NATURAL HISTORY YALE UNIVERSITY 1935 ‘k PEABODY MUSEUM OF NATURAL HISTORY TRUSTEES James Rowtanp ANGELL, Pu.D., Litr.D., LL.D. His Excettency THE Governor oF CoNNECTICUT, ex Officio. Samvuet Hersert Fisuer, LL.D. Howey Cueney, M.A. Vance CrisweLt McCormick, LL.D. Frep Towstey Murpuy, M.D., M.A. FrepericK Trusree Davison, LL.D. DIRECTOR RicHarp Swann Lu tt, Pu.D., Sc.D. CURATORS Epwarp Sarispury Dana, Pu.D., Curator of Mineralogy, Emeritus. Grorar Grant MacCurpy, Pu.D., Curator of Anthropology, Emeritus. Cuartes Scuucuert, LL.D., Sc.D., Curator of Invertebrate Paleon- tology, Emeritus. Stranuey CrirteNDEN Batt, Pu.D., Curator of Zoology. Cart Owen Dunsar, Pu.D., Curator of Invertebrate Paleontology. Wiriiam Esenezer Forp, Pu.D., Curator of Mineralogy. RicuHarp Swann Lutt, Pu.D., Sc.D., Honorary Curator of Vertebrate Paleontology. CorNnetius Berrien Oscoop, Pu.D., Curator of Anthropology. Avsert Emer Parr, M.A., Curator of the Bingham Oceanographic Collection, and Scientific Director of the Yale Oceanographic Expeditions. Matcoim RutTHerForD THorPE, Pu.D., Curator of Vertebrate Paleon- tology. Martin Davin Burkenroap, Assistant Curator of the Bingham Oceanographic Collection. Froruiicn Guiapstone Rainey, M.A., Assistant Curator of Anthro- pology. ADVISER IN GEOLOGY Cuester Ray Lonewettz, Pu.D. RESEARCH ASSOCIATES Grorce Grant MacCurpy, Pu.D., Research Associate in Prehistoric Archeology, Emeritus. Cuartes Marcus Breper, Jr., Research Associate in the Bingham Oceanographic Laboratory. He.imovt ve Terra, Pu.D., Research Associate in Geology. Matcotm Routuerrorp TnHorpe, Pu.D., Research Associate in V erte- brate Paleontology. CuarLes Epwin Weaver, Pu.D., Research Associate in Invertebrate Paleontology. RESEARCH ASSISTANTS James Brooks Knicut, Pu.D., Research Assistant in Invertebrate Paleontology. Ciara Mar LeVeneg, B.A., Research Assistant in Invertebrate Paleon- tology. Netpa Emetyn Wricut, M.A., Research Assistant in Vertebrate Paleontology. DOCENTS Mitprep Cynruia Bruian Porter, M.A., in charge. Dorotuy Emma Arno tp, B.A. Gertrupe Horcuxiss Ciark. it Oe i ole + ‘ + lan \y ’ ‘ iY aX! i) uu j roy i ; f LU i] fy f i, is . i fj i" 7 i] . ) : ‘ ¢ . i 7 _ i & i i ; 4 ; ‘? wx Le Hh f é @ 7 THE PEABODY MUSEUM OF NATURAL HISTORY BULLETIN 4 MIOCENE MARINE MAMMALS FROM THE BAKERSFIELD REGION, CALIFORNIA BY LESLIE E. WILSON NEW HAVEN THE PEABODY MUSEUM OF NATURAL HISTORY YALE UNIVERSITY 1935 TO HUGH GIBB 1860-1932 Chief preparator for O. C. Marsh and the Yale Peabody Museum for fifty years, in tribute to his skill in preparing fossil vertebrates and wm gratitude for his kindly aid and instruction in preparation work, this bulletin is dedicated. CONTENTS Pee MIOWICOSTAEIIES | Sey wis glee iaa'e #16 a 6 als ¥eiWrave'm! oi. © loce’a e nieiiere 0m 0's Pocation and geology Of area.) . 26. ect ce cent tele one Rare eATNG CULO YM ey te Nae eee lal i oaiiayal a jaletaney p.atelerels ‘yiaieve be a'eo sunies iy ed eC GC ct eee lars ear oP oleralal si poke, cis olor a la Blm akela: wate! svalins are SupOLder sOGOmLOCELL usta. aoa cine sie iels a eicierd fel 00a she oa! © ol ays EE apaantby ey yaa Lee retry onster olen nin sirstrensiei ake! of ois enatel a « aires Allodelphis, new QeNUS....... 26.2 e essen ereecens Allodelphas pratiz, new SPECleS. 0a... -- 2+ - == - >> Wigerodel mhanus, Mew) REUMSI: oer = aero) s ola) iy . | ; i I | ae os Beanie ‘i — es nbe Hit | ye ata as My An nee (k i } | ear vee iW Wa meet Pi ay ae ay i i i ; ve ‘+7 aly b byuty f 4 ‘os We A a ib i } \ } ad i ; I Ti RI Co Ni oY 7 } : | J Mi ; : “ 5 } - ; ' I ea | ’ “Ty 4! ot i . Maia wt ier) igh Aq ‘iim i A ‘| i a ie +d ial t Hay CRUMALD | Ey" las Ve APY Pig CUD iy a ri . | Py CET alate 6 aoe Se 4 , eolare 3 ey ip?)- | ed 4 i ¥ ae | i if , iT. is i" hie : ‘7 L ; ; a é ® a e Fe, B inhale m noe aoe ) - i he hd i) by a. ’ o ey MARINE MAMMALS FROM THE MIOCENE OF THE BAKERSFIELD REGION, CALIFORNIA ye ; 7 Bitpare Lee Phd At HEAD ae Pe) Rae ee at Bp)’ " es iy WAR { i ie ‘ ACKNOWLEDGMENTS The most important acknowledgment is to the discoverer of the first fossil which leads to the acquisition of a collection; and, accordingly, first mention in this paper goes to Mr. Charles A. Pratt, a student in the writer’s petroleum technology class of 1928-1929 in Bakersfield Junior College, Bakersfield, California, who discovered the skull and vertebrae of Allodelphis pratti (n. gen. et sp.) in the autumn of 1928 and brought them to the writer for identification. For the next two years, Mr. Pratt, the writer, Mr. Thurston V. Little of Shafter, California, and others made regular trips to different localities in the southern end of the San Joaquin Valley, discovering new fossil locations and exca- vating and transporting fossil material. Thanks are due to the members of the writer’s classes in petroleum technology, 1928— 1930, for excavation work. To the officials of Bakersfield Junior College, Dean Grace Van Dyke Bird and Principal H. A. Spindt, are due thanks for the privilege of storing and displaying the fossils of this collection in Bakersfield. To Mr. H. E. Ireland thanks are due for the careful packing of parts of the collection for shipment to Yale University. The freight on the larger part of the collection, from the shipping points of Palo Alto and Bakersfield, California, to New Haven, Connecticut, was paid by Yale University. The hardness of the matrix required some new mechanical grinding equipment, for the setting up of which and the making of accessory equipment the writer is indebted to Mr. F. C. Herpich and Mr. William Conway of the Peabody Museum staff. The preparation of this collection has been done entirely by Mrs. L. E. Wilson and the writer. Outline figures were drawn by the writer. The shaded drawings were made by Miss Joy Stilson of the Peabody Museum staff, and financed by the Marsh Publi- cation Fund. Publication of the present paper has been made possible, also, by the Marsh Publication Fund through the good offices of Director Lull. The writer regrets that limitation of 10 PEABODY MUSEUM OF NATURAL HISTORY funds prevents the publication, at this time, of sufficient figures to amplify fully the descriptions in this paper. To Dr. Charles W. Gilmore and Dr. Remington Kellogg of the United States National Museum the writer expresses his gratitude for their assistance and courtesy during the time the comparative work was being done at the National Museum. LOCATION AND GEOLOGY OF AREA The area which yielded the fossils described in this report is located at the southern end of the San Joaquin Valley, California, adjacent to the Sierra Nevada Range. Perhaps the first verte- brate fossils collected by scientific men within a dozen miles of this area were the teeth picked up by W. P. Blake’ and described by Louis Agassiz? as remains of sharks, skates, and mackerel. Professor Agassiz states that this represented the first discovery of shark teeth west of the Rocky Mountains and remarks that ee ° their value to science . 1s further enhanced by the peculiar relations they bear to similar fossils found in the Atlantic states 29 and in Europe...” The horizon from which Blake’s fossils came is probably the same as that exposed in the “Fullers Earth” mine in Granite Canyon, about four miles north of Poso Creek,® and exposed, also, at the well-known “Shark Tooth Hill,” Sec. 25, T. 28 S., R. 28 E., Mt. Diablo Base and Meridian, only a few miles east of the Kern River Oil Field. From “Shark Tooth Hill” bones of cetaceans, sea lions, and seals have been exca- vated.* This locality likewise furnished abundant shark teeth described by the late David Starr Jordan, among them the well- known Carcharodon temblorensis Jordan.’ The history of dis- coveries of a geologic and paleontologic nature in this general locality before 1911 is contained in an article by F. M. Anderson.°® Long before that date, and since, the great activity in the devel- 1. Pacific R.R. Reports, vol. 5, pp. 164-173, 313-316, 1857. 2. Agassiz, L.—Notice of the fossil fishes found in California by W. P. Blake. Am. Jr. Sci. and Arts, 2d ser., vol. XXI, pp. 272-275, 1856. 3. Hanna, G. D.—Miocene marine vertebrates in Kern County, California. Sci., n. s., vol. LXI, pp. 71-72, 1925. 4. Kellogg, R.—Pelagic mammals from the Temblor formation of the Kern River region, California. Proc. Cal. Acad. Sci., 4th ser., vol. XIX, no. 12, pp. 217-397, 1931. 5. Jordan, David Starr—New sharks from the Temblor group in Kern County, California, collected by Charles Morrice. Proce. Cal. Acad. Sci., 4th ser., vol. XV, no. 8, pp. 257-261, 1926. 6. Anderson, F. M.—The Neocene deposits of Kern River, California. Proc. Cal. Acad. Sci., 4th ser., vol. III, pp. 73-148, 1911. 12 PEABODY MUSEUM OF NATURAL HISTORY opment of oil fields in the Kern River region had led to intensive study of the sedimentary formations by geologists of various oil companies; but for economic reasons their information exists only in private reports and maps. The topography of the east side of the San Joaquin Valley in this locality consists of rolling foothills of the Sierra Nevada and has little relation to the underground structure. The gen- eral elevation of the area of this report is about 950-1250 feet (Woody Quadrangle, U. S. G. S.). The general stratigraphic and structural relations in the Mt. Poso Oil Field, the area nearest the basement complex that, so far, has been described, were clearly set forth by Wilhelm and Saunders in 1927.‘ The information presented by that report was obtained from a series of well logs and from areal mapping. The surface formations range from the basement complex of Jurassic age along the eastern border of the area, to uppermost Kern River of Pleistocene and Recent age farther away from the mountains. The dominant structural feature of the area of this report is faulting, a character common to the whole east side of the Valley.® The faults are principally of the normal type, and have been dated by the penetration of the faults by the drill at various horizons and localities during the process of drilling for oil in the area. 7. Wilhelm, V. H., and Saunders, L. W.—Report on the Mt. Poso Oil Field. 12th Ann. Rept. State Oil and Gas Supervisor, Cal. State Min. Bur., vol. 12, no. 7, January, 1927. 8. Fox, L. S.—Structural features of the east side of the San Joaquin Valley, California. Bull. Am. Assn. Pet. Geol., vol. 13, no. 2, pp. 101-108, 1929. PALEONTOLOGY This collection of marine mammals includes toothed cetaceans, a cetothere, sea lions, and a seal. Order CETACEKA The cetaceans described in this report show that the general configuration of the cetacean skull was already attained by the end of Lower Miocene time, and its similarities to the skulls of modern forms show that the only subsequent changes have been those in individual bones. The characteristic cetacean features of these skulls, namely, the elongation of the maxillaries and premaxillaries, with the posterior broadening of the maxillaries as they overspread the frontals, the shortening of the nasals with their retreat in a posterior direction, the posterior migration and compression of the frontals, the rigidity of the supraoccipital, and the modern aspect of the narial passages, are all represented in the Vaqueros- Temblor transition deposits. The contrast, however, between the characters of the individual bones of these specimens and modern porpoises—for example, the increasing thinness of the maxil- laries, the further decrease in size of the nasals, and the assump- tion of varied shapes in the supraoccipital of recent forms, as contrasted with the comparatively thick maxillaries, longer nasals, and larger frontals of Miocene forms—indicates that the general evolutionary results were established before the begin- ning of Miocene time, and that later developments have been specialization of parts. Suborder ODONTOCETI Family DELPHINIDAE ALLODELPHIS,’ new genus 10 Genotype.—Allodelphis pratti,*® new species. 9. ddXos, strange; deddis, dolphin. 10. Named in honor of its discoverer, Mr. Charles A. Pratt of Bakersfield, California. 14 PEABODY MUSEUM OF NATURAL HISTORY Diagnosis —Resembling Argyrocetus joaquinensis™* in the pres- ence of elongated nasals, but differing from it in the reduced exposure of the frontals on the vertex, the relatively large occip- ital condyles, and the conformation of the occiput. Rostrum elongated (distal portion missing), vertex elevated, postero- internal angles of maxillaries rather closely approximated on vertex, nasals long and relatively narrow, premaxillaries nar- rowed, lambdoidal crests prominent, and occiput flattened. Allodelphis pratti, new species Figs. 1-3 Holotype.—Cat. No. 13408 Y. P. M. The skull is incomplete with the major portion of rostrum missing, the right supraorbital process is destroyed at extremity, the bones inclosing the internal choanae are imperfectly pre- served, and the right exoccipital is incomplete. Both tympanic bullae and the left periotic bone are missing. Right periotic is complete. No teeth were preserved with this skull. The skeletal elements consist of the complete right humerus, left half of atlas, thirty incomplete vertebrae, and a few fragments of ribs. Type locality—S. W. 14 of Section 12, T. 26 S., R. 28 E., Mt. Diablo Base and Meridian. This locality is on the south slope of a hill shown as elevation 1240+ feet on the Woody Quadrangle, U. S. Geological Survey. It is about 434 miles southwest of Woody, Kern County, California. Horizon.—This fossil bed occurs in a hard, white-to-brown sandstone which reaches a thickness in excess of 60 feet locally, the whole member (Pyramid Hills Sand) attaining a thickness of 160 feet. The Pyramid Hills Sand is the equivalent of the “A” zone of F. M. Anderson.’? At the outcrop in this locality, the Pyramid Hills Sand is underlain by 50 feet of the mudstone reefs of the “Walker,” which, in turn, lies on the Basement Complex. The fossil bed is located in that part of the section which is 11. Kellogg, R.—A Miocene long-beaked porpoise from California. Smith- son. Mise. Coll., vol. 87, no, 2, pp. 1-11, pls. 1-4, 1932. 12. Anderson, F. M.—Op. cit. MIOCENE MARINE MAMMALS 15 debatably Temblor or Vaqueros, in what might be called the Temblor-Vaqueros transition zone. The skull and skeletal parts of this animal were discovered by Mr. Charles A. Pratt of Bakersfield, California, in the autumn of 1928. ‘The excavation of most of the specimen was made by Mr. Pratt; and he transported the specimen to the Junior College in Bakersfield, where it was partially cleaned and put on display by the writer. Subsequent search by Mr. Pratt and the writer led to the accumulation of additional skeletal parts. Skull Dorsal view.—The outstanding characters are the flattening of the dorsal surface, the posterior elongation of the narrowed premaxillae, the flaring lateral lambdoidal crests, a conspicuous median crest on the supraoccipital, and the vertical, uncurved narial passages. The premaxillae, anterior to the narial open- ings, are narrow, with a thin, rounded external edge and a thicker, angular internal edge, and show a broad, deep, longitudinal groove in the center. The premaxillae curve inward behind the narial passages, encroaching upon the nasals laterally and restricting the exposure of the frontals on the vertex. The longi- tudinal groove in the center of the premaxilla passes to the external edge and disappears 30 mm. in front of the level of the anterior edges of the narial passages. The premaxillae widen somewhat on the internal side at approximately the level of the maxillary notches, and then narrow suddenly to make room for the narial passages. Concurrently, at the level of the narial openings, the position of the premaxillary changes from hori- zontal to steeply inclined. At the level of the anterior edges of the nasals, the steep inclination is lessened somewhat; and the premaxillae, also, are emarginate at their posterior ends, which lie about 28 mm. behind the anterior edge of the nasals. The maxillae underlie the premaxillae throughout the length of the latter, extend posteriorly to the supraoccipital, overlie the frontals, and lie against the nasals internally. They do not entirely overspread the supraorbital processes of the frontals, but 16 PEABODY MUSEUM OF NATURAL HISTORY Fig. 1. Allodelphis pratti (holotype), dorsal view. x 3/8, anterior foramen anterior notch choana exoccipital foramen magnum frontal maxilla mesethmoid notch for jugular leash nasal occipital condyle olfactory foramen optic canal Pa Pal. loc. Pal. vac. Pmx parietal location of palatine palatine vacuity premaxilla post-orbital process presphenoid pterygoid supraoccipital supraorbital process squamosal vomer zygomatic MIOCENE MARINE MAMMALS Nig leave an uncovered portion of more than 13 mm. at the anterior edge. The left maxilla shows three small foramina in the region of the maxillary notch. One lies near the external edge and behind the level of the maxillary notches ; and two near the center of the maxilla, separated by a distance of 6.8 mm., just anterior to the level of the maxillary notches. The frontals are elongated in a lateral direction, and their median suture is indistinct. The nasals are long, narrow bones, considerably wider at the anterior than at the posterior end, elevated at both ends, and supported anteriorly by the meseth- moid. The right nasal is slightly longer than the left, reaching 30 mm. along the median suture. The left nasal, along the same line, is 28.5 mm. The width of the right nasal at the anterior edge is 17.5 mm. and of the left, 14.0 mm. Posteriorly, the right nasal has a transverse width of 8 mm. and the left, the same width. The presphenoid plugs the posterior end of the meso- rostral gutter and is, there, a wide spongy bone. In a posterior direction, it becomes more narrow and more elevated. The mesethmoid sheathing the presphenoid reaches well above the pre- maxillae in a vertical direction and extends posteriorly to the nasals, to form the highest point of the dorsal surface of the skull. Posterior view—The supraoccipital is broadly expanded, with flaring exterior edges directed posteriorly. A well-defined carina extends in a dorso-ventral direction from near the top of the supraoccipital toward the occipital condyles. In this specimen, a view of the lower part of this crest is cut off by the presence of the atlas, which has been thrust upward from the occipital condyles and now rests just above them against the supraoc- cipital. ‘The above-mentioned carina divides near the top and forms, on each side, a smaller crest which extends laterally on the supraoccipital from a median line to near the level of the postero- external angle of the maxillary. Above the junction of these subsidiary crests is a short, transverse crest on the dorsal edge of the supraoccipital. Near the crests, the supraoccipital is rugose and thick but becomes smooth and paper-thin away from them. The occipital condyles are broadest near the base and 18 PEABODY MUSEUM OF NATURAL HISTORY taper considerably toward the apex (cf. Argyrocetus, Kellogg, p- 6). The high part of the articular surface is near the middle of the condyle. The condyles show sharp, slightly overhanging ridges on the exterior edges, which become rounded on the dorsal side. The necks of the condyles are distinct but short and but little smaller than the exterior edges. The basal intercondylar gap is 22.7 mm. The exoccipitals are heavy bones which descend fanlike from the lower part of the occipital condyles. The exoc- cipitals are separated from the lateral processes of the basioc- cipital by the deep notch for jugular leash. The foramen magnum is suboval in outline with a greatest width of 40 mm. and a vertical diameter of 24 mm. The internal edges of the condyles overhang the foramen magnum. Lateral view.—The low, flat brain case is a noticeable peculiar- ity of this skull, as is the sharp backward arching of the lateral portion of the lambdoidal crest and the close approach of the supraorbital process of the frontal to the zygomatic process of the squamosal. The zygoma is stout and moderately curved and has the plane of its external surface practically parallel to the sagittal axis of the skull. Its dorsal aspect shows a steep external slope downward and forward from a broad vertex, and a steeper, inward, posterior slope. The greatest length of the left zygo- matic process is 67 mm.; its dorso-ventral diameter anteriorly is 33.1 mm. The orbit is rounded anteriorly and posteriorly, with the posterior slope somewhat steeper. ‘The supraorbital process of the frontal is broken on both anterior and posterior edges on both sides of the skull. The thinnest point is above the center of the orbit, where the process shows a thickness of 3.9mm. From this point, rapid thickening takes place in both anterior and pos- terior directions. Its dorsal aspect, while irregular, is noticeably flattened. The superimposed plate of the maxilla does not cover the supraorbital process entirely but leaves a fairly wide border at the exterior edge. The external edge of the frontal underlying this portion of the maxilla is indiscernible. In the lateral view, the backward bowing of the lateral edge of the supraoccipital is conspicuous (similar to Argyrocetus). ‘The vertex of the skull MIOCENE MARINE MAMMALS 19 is long and flat, and the descent from it to the rostrum is gradual. The parietal is curved laterally. A deep depression is formed on the squamosal just above the zygoma. The exoccipitals are wid- ened ventrally and become thinner toward their upper limit. Ventral view.—The vomer is visible from the anterior end of the specimen to its point of contact with the basioccipital. At the anterior end of the specimen, near the base of the rostrum, the ventral surfaces of the maxillae are separated only by the narrow, rounded edge of the vomer, which appears as a ridge Fig. 2. Allodelphis pratti (holotype), lateral view. x 3/8. For explanation of lettering, see Fig. 1. between the maxillae. In a posterior direction, the vomer shortly appears and is well exposed at the palatine vacuities; it is seen to be triangular in shape, with the apex on the ventral side and the broad base lying dorsal to this. At the anterior edges of the narial openings, the vomer shows lateral compression but becomes wider at the posterior edges of the narial apertures. The pala- tine vacuities are noticeably large. Interiorly, the narial open- ings are bounded chiefly by the vomer and partially by the rapidly thinning posterior surfaces of the maxillaries. Exte- riorly, they are bounded by the maxillae, and the pterygoids, with their external reduplications. The narial apertures are elliptical 20 PEABODY MUSEUM OF NATURAL HISTORY MEASUREMENTS OF SKULL* Total length’ of skull ‘as’preserved: 5.5 Ws sca «seas 235 Transverse diameter of skull between outer surfaces of zygo- MALIC SPTOCESSESG Gem 2 loieye ite ae as oan eo eee 194 Distance across skull between outer margins of exoccipitals.. 171.5 Distance between inner margin of left occipital condyle and outer margin .of left vexoccipital’..\. ii2-..0-. <2. nee or 83 Distance between inner margin of right occipital condyle and outer margin ‘of ‘right: exoccipital.: = ono ae eee 36.5 Maximum transverse breadth from exterior tip of tuberosity at base of anterior process to extremity of pars cochlearis at level of fossa for-head of malleus. ......o...-2.s0-me 24 Greatest dorso-ventral depth from most inflated portion of dorsal face of pars cochlearis to projection on the ventral face at level of cerebral orifice of aqueductus vestibuli.... 17 Distance between nearest edge of fenestra rotunda and dorsal tip Of ANtETIGr PLOCEsS.. aie. oie re « Woxe rae, | Wiah's'* fajar ugha siai we ayes Mer als 0) 9 41 Distance to posterior edge of vertebrarterial canal measured from edge of ‘facet for articulation with axis). 23. 0\)s/ej.0.402 0s 39 Width of vertebrarterial canal on internal edge............... 13 Vertebrae The vertebrae found with this skull include fourteen dorsals (of a size which indicates that they might belong to M. kelloggi), all of which are located anterior to the transitional dorsal and belong to two or more individuals. All have anterior and pos- terior lateral facets for articulation with the heads of the ribs. The centra range in length from 47 mm. to 72 mm. measured along the median line of the superior side of the centrum, the anterior face measuring, for the longest, 55 mm. vertically and 64 mm. transversely, and for the shortest, 54 mm. vertically and 75 mm. transversely. 38 PEABODY MUSEUM OF NATURAL HISTORY Macrodelphinus kelloggi (Individual 2) Figs. 5-8 Referred specimen.—Cat. No. 18403 Y. P. M. This specimen consists of the rostral portion of a skull broken off transversely just behind the maxillary notches and near the anterior end, the preserved part being 560 mm. in length. Asso- ciated with the rostrum were a right mandible, atlas, axis, third, fourth, and sixth cervicals, sixth dorsal vertebra, right radius, right ulna, anterior half of the shaft of the left humerus, carpal, one nearly complete sternal plate and part of another, and parts of seven ribs. Since all of these parts are from a single small block of sandstone, and since the adjoining parts articulate properly, all are assumed to have belonged to the same porpoise as the rostrum. This specimen, fortunately, supplies some of the parts of the rostrum that are missing in the type. This skull and associated skeletal parts were discovered by Mr. Charles A. Pratt, im 1929: Locality.—About 200 feet northeast of the pit in which the holotype of Macrodelphinus kelloggi was found. Horizon.—P yramid Hills Sand, approximately 50 feet higher in the section than the horizon of the holotype. Skull Dorsal view.—As in the type specimen, the rostrum is heavy and elongate. The premaxillae, which lie nearly horizontally at the level of the maxillary notches, gradually assume a nearly vertical position concurrently with their anterior extension. The width of the premaxilla is constant, while the maxilla decreases rapidly in width anteriorly. The rostrum shows the maxillae and premaxillae only for a length of 550+ mm. from the maxillary notches. At the anterior end of the rostrum as _ preserved, the bones are thick and the premaxillae wide. The maxillary notches and the anterior end of the rostrum are higher than the central part, and the maxillae are noticeably concave later- 39 MIOCENE MARINE MAMMALS Fig. 6. MOU (CMAQ WAKE Fig. 5. Br MRA SRNR SS SAN Fig. 5. Macrodelphinus kelloggi (individual 2), dorsal view. x 1/4. Fig. 6. Macrodelphinus kelloggi (individual 2), ventral view. x 1/4. 40 PEABODY MUSEUM OF NATURAL HISTORY ally. The right maxilla contains two foramina, the posterior rim of the larger one being on a level with the maxillary notch. The second foramen is located 42 mm. anterior to the first. In the left maxilla, on a level with the anterior foramen of the right maxilla, is a foramen of the same size. Each side of the rostrum has an additional foramen. The foramen of the right side has its posterior border at the contact of the premaxilla and maxilla, at a point 300 mm. in front of the right maxillary notch. This foramen is deep and narrow and measures 67 mm. antero- posteriorly and 214 mm. transversely at its posterior limit; the width increases anteriorly to 10mm. The corresponding foramen of the left side lies 39 mm. posterior to the level of the right foramen and is also somewhat wider than the latter. While originating at a point common to both maxilla and premaxilla, each groove is bounded by the premaxilla alone at its anterior end. The maxillae and premaxillae are in contact throughout their length. The right premaxilla has been forced slightly over the left on the mid-line, so that the premaxillae are unequal in height. Ventral view.—The outstanding characters exhibited in this view are the curvature of the alveolar series, the amount of exposure of the vomer and its width, and the thickness of the palatines. The first alveolus of the right maxilla occurs 49 mm. in front of the maxillary notch. On this side, there are 35 alveoli and teeth in a distance of 491 mm. The teeth occupy the following alveoli, counting forward from the most posterior alveolus: 2, 5, ‘7, 11, 17, 18, 19, 21, 22, 23, 26, 28 to 34 inclusive. The teeth in alveoli numbered 2 and 7 are complete and in 26 nearly so. The teeth in alveoli numbered 5, 18, 29 to 34, inclu- sive, lack the crown. A good idea of the dentition, however, can be had from this specimen. The size of the alveoli shows but little variation, the average antero-posterior diameter being about 11 mm. and the transverse diameter approximately the same. The variation in size, and sometimes in shape, is individual rather than directional. In the left alveolar series there are 39 alveoli in a distance of 482 mm. Thus, the left maxilla bears four more teeth MIOCENE MARINE MAMMALS 41 than the right, and the explanation of this numerical difference is found in the small size of the six posterior teeth of the left maxillary. The left side has incomplete teeth in alveoli numbered 1, 2, 3, 17, 18, 20, 21, 22, 24. Only one, that in alveolus num- bered 22, has part of the crown remaining. ‘The vomer, begin- ning at a point 148 mm. in front of the maxillary notch, is exposed between the maxillae for a distance of 160 mm. measured along the median line. At the point of its first appearance, the vomer is only slightly arched but rises anteriorly to a sharp keel, in a space of 30 mm., which continues as far as the vomer is visible. The intermaxillary gap, filled by the vomer, amounts to 20 mm. at its widest place and narrows anteriorly to the point at which the vomer disappears under the maxillae. The anterior ends of the palatines are preserved. They descend gradually from their point of origin to the break which terminates the specimen posteriorly. The palatine vacuities are partly shown. Their anterior ends are separated by a distance of 40 mm.; and at the break on the posterior end of the specimen, the left vacuity is 8 mm. from the median line. The anterior part of the base of the right jugal is preserved, and it is seen to have a long base in an antero-posterior direction and to be narrow transversely. The fragment passing externally to connect with the lacrimal shows no lacrimal suture. MEASUREMENTS OF SKULL 2 Maximum length of specimen, measured from break just be- hind! maxillary notch’to anterior breaks. so... 00... 4. << 560 Breadth. of rostrum at maxillary notched .2/0 5.4). es ee ac 4 3 176 Breadth of left premaxilla at level of maxillary notch....... 40 Breadth of right premaxilla at level of maxillary notch..... 39 Breadth of right maxilla at level of maxillary notch........ 45.2 Breadth of left maxilla at level of maxillary notch......... 44,2 Depth of rostrum at level of maxillary notch.............. 86 Depth of rostrum at level of 34th alveolus of left maxilla... 47.5 Breadth of left maxilla at level of 34th alveolus........... 18.4 42 PEABODY MUSEUM OF NATURAL HISTORY Fig. 7. Right mandible of Macrodelphinus kelloggi (individual 2), dorsal view. x 1/4. Fig. 8. Right mandible of Macrodelphinus kelloggi (individual 2), internal view. x 1/4. MIOCENE MARINE MAMMALS 43 Right Mandible Part of the anterior end of the right mandible is missing, and the posterior end is broken off 57 mm. behind the posterior border of the first (most posterior) alveolus of the jaw. The most striking character of the mandible is the length of the symphysis (800+ mm.; anterior end of jaw missing) and the outward bending of the postero-ventral part of the ramus. The axis of the alveolar series is curved internally from its posterior end to the symphysis, where it becomes practically straight. The mandible contains 32 alveoli in a distance of 484 mm. No teeth are preserved in this series of alveoli. The whole jaw becomes thinner anteriorly both dorso-ventrally and transversely. MeraAsurEMENTs oF Rigut MANDIBLE Total length of mandible as preserved, measured along the cury- BiUhesOL tie ALVEOIAL (TOOVE. io .c.c1s) ab ihsinis: san bus 150 Maximum transverse width of deltoid process............... 26 Maximum dorso-ventral length of deltoid process (including Ovid, PELtionwOnly yoy 504 oe sora csceee esters oe ae eects 34 Radius The right radius is complete except for a piece of the internal border adjoining the distal articular face. The bone is a simple shaft, concave on the external and posterior sides, convex ante- riorly, straight internally, and enlarged at both ends. The radius is wide, as compared with the ulna, and practically constant in 50 PEABODY MUSEUM OF NATURAL HISTORY width throughout the length of the shaft. The crown is slightly convex, its supporting shaft rugose (no distinct neck is present), and the tubercle (radial tuberosity) a narrow rugose ridge extending internally from the external face for about two-thirds the width of the neck. The articulatory surface for the scapho- lunar has the shape of an elongate ellipse. The anterior edge of the bone is a rounded ridge. The posterior border is gently rounded near the tubercle but becomes a narrow ridge over the distal half and bears, near the distal extremity, a flat surface (facet for ulna) adjoining the ridge on the external side. MEASUREMENTS OF Raprius Maximum length’ along anterior edge (5 <2). 66.5 nig oo wel iereaee 152 Maximum .Jeugth along, posterior ‘edpe)..:):).4). ea eee 137 Maximum extero-internal diameter of shaft at edge of crown... 37 Maximum antero-posterior diameter of shaft, measured from anterior ‘edge to facet above tubercle...) ..52.- 20-6 - nee 46 Maximum antero-posterior diameter of shaft at middle....... 50 Maximum antero-posterior diameter of articulatory surface for scapholunar: 2 c/s ve ayoiee,ceerciiete om elaine ae veeeie uae 50 Maximum extero-internal diameter of same...............05- 26 Ulna The right ulna is incomplete, having a gap in the shaft of about 10 mm. The gap is located 28 mm. above the distal end. The outstanding character of this bone is the great antero- posterior width and dorso-ventral height of the compressed olecranon process. This process shows evidence of erosion at its posterior edge and internal surface. The length of the ulna is about the same as that of Mesoplodon grayi (U. S. N. M. No. 49880), but the olecranon process of Macrodelphinus kelloggi (specimen 2) is much wider antero-posteriorly. The sigmoid cavity is broad throughout, and its surface is irregular. The radial notch is of moderate depth, rugose, and set into the head of the shaft. The shaft is concave on both anterior and posterior edges just below the radial notch, reaches its narrowest portion at a distance of 38 mm. below the distal edge of the support of the MIOCENE MARINE MAMMALS 51 radial notch, and then increases in size in a distal direction. External and internal borders of the ulna are straight. MeEAsurEMENTS oF ULNA Internal antero-posterior depth of sigmoid cavity............ 33.5 External antero-posterior depth of sigmoid cavity........... 25 Extero-internal diameter of anterior surface of sigmoid cavity.. 31 Maximum antero-posterior depth of ulna from vertical face of radial notch to posterior end of olecranon process........ 80 Height of olecranon process above surface for articulation with REQEIMC AM aera sis Cte orerrtaicte ws io ste a te Oe Saraas sea \oyele aa 45 Minimum antero-posterior diameter of shaft................ 35.6 Minimum extero-internal diameter of shaft measured at same point as preceding (38 mm. below support of radial notch) 21 Maximum antero-posterior diameter of distal end............ 51 Maximum extero-internal diameter of distal end............. 20 Carpal The right scaphoid, or radiale, is practically complete and shows considerably more thickness on the posterior than on the anterior side. The articular surfaces are rugose. Because of its shape and since it matches the anterior part of the distal articular surface of the radius, it is designated the scaphoid and allocated to individual 2. MEASUREMENTS OF SCAPHOID Antero-posterior diameter of external face..............ese00e 22 Dorso-ventral diameter of external face. .......50/. ec cce caves 20 Maximum extero-internal diameter of posterior face.......... 21 Maximum extero-internal diameter of anterior face........... 11 Sternum Parts of two sternebrae, which are designated as first and third by comparison with Orcinus orca (U. S. N. M. No. 23004), are assigned to individual 2. The third sternebra is nearly complete. The first shows that the left anterior side has about half of the surface for the articulation of the cartilagi- 52 PEABODY MUSEUM OF NATURAL HISTORY nous part of the left first rib, and has a posterior extent of 150 mm. The surface for the rib articulation is wide and deeply concave, and the anterior edge bears a projection about 23 mm. long that thins rapidly anteriorly to a sharp edge. The third sternebra is much thicker at the anterior end than at its posterior border, its superior and anterior faces being rugose and the left anterior side showing a surface for articulation with the costal rib. The third sternebra has a median length of 68 mm., an anterior width of 67 mm., a posterior width of 52 mm., an anterior thickness of 16.5 mm., and a posterior thickness of 10 mm. Ribs Of the six ribs preserved with this specimen, none is complete. Five have the proximal articulatory processes. By comparisons with Mesoplodon grayi (U. S. N. M. No. 49880), a whale with skeletal parts of about the same size as those of individual 2 of Macrodelphinus kelloggi, the ribs were placed as follows: first and seventh left, third, fifth, sixth, and tenth right. The first left rib is broad and flat and considerably expanded near the tuberculum. ‘The tuberculum is large, ovoid, and considerably larger than the elliptical capitulum, which is carried on a broad neck. The anterior edge is thick and tapers gradually to about one-third of the anterior thickness, at the posterior edge. The shaft is of constant width and regularly decreasing curvature distally. The left seventh rib is more rounded and much narrower than the first. The curvature is strong throughout. The shaft is constant in shape and size. The tuberculum is strongly concave and much larger than the capitulum. The capitulum is consid- erably larger than its supporting neck. Just below the tuber- culum, a ridge slightly overhangs the shaft posteriorly and extends for a distance of 65 mm. The third right rib lacks the tuberculum and capitulum. The rib is preserved for a short distance proximally beyond the angle, and the shaft, as present, is about 100 mm. in length. The MIOCENE MARINE MAMMALS 53 general shape is that of the first, except that the shaft begins to thicken anteriorly and to contract in width distally. On the anterior edge is a sharp angle directed posteriorly. The fifth right rib lacks the capitulum and the distal half of the shaft. The tuberculum is semi-triangular in shape, with the apex on the vertebral side. A rounded ridge posteriorly over- hanging the shaft occurs a short distance below the tuberculum and extends distally a distance of 43 mm. The shaft becomes well rounded distally. MEASUREMENTS OF Riss Greatest length in a straight line (as pre- REEVEGI) fc 2 a5 315) 5c se: Greatest width of shaft HEPATIPIE I cia.. 81s se» 6 Distance between ex- ternal margin of tu- berculum and anterior margin of capitulum.. Greatest thickness’ of shaft near center..... Greatest diameter of ar- ticular facet on head CREEL oiteciats 3 sscrae Ore Greatest diameter of ar- ticular facet on tu- berele of rib........ Least breadth of neck... The sixth right rib has only the vertebral end and a short length of the shaft preserved. It is like the fifth except that the tuberculum is irregularly triangular and the posteriorly over- hanging ridge of the ventral side continues to the tuberculum. 54 PEABODY MUSEUM OF NATURAL HISTORY The tenth rib is flat and has no tuberculum. The capitulum is only partially preserved and is thicker posteriorly than ante- riorly. The rib becomes rounder in a distal direction. ? Macrodelphinus kelloggi Fig. 9 Specimen.—Cat. No. 138412 Y. P. M. This specimen consists of two fragments of the rostrum, pre- sumably from near the distal end, separated from each other by a short interval. Locality.—_N. W. 14 of Section 13, T. 26 S., R. 28 E., M. D. B. & M., at the top of a hill shown in this locality on the Woody Quadrangle, U. S. Geological Survey, about 5 miles southwest of Woody, Kern County, California. This specimen was found by the writer in the spring of 1930. Horizon.—Near the top of the Pyramid Hills Sand described above. These two rostral fragments are tentatively referred to Macro- delphinus kelloggi, although it is recognized that more complete material may eventually show that the relationships are with the family Iniidae instead. These fragments belong near the terminal end of the rostrum, and both of the specimens heretofore described lack the anterior end of the rostrum. No direct comparisons are, thus, permitted. The alveoli are approximately as large as might. be expected to occur on the distal end of the rostrum. The lengths of the alveoli vary from 8 mm. to 11 mm. at the ventral surface of the alveolus. The septa vary in thickness from 1.5 mm. to 4 mm. measured at the ventral surface. The widths of the alveoli average about 9 mm. in the anterior fragment and in the posterior fragment reach as little as 6 mm. as a minimum, with an average of about 7 mm. Although the contours of the mesorostral gutter change rather rapidly in these two fragments, it is still uncertain as to whether or not a continuation of the mesorostral gutter in individuals 1 and 2 of M. kelloggi would have assumed the shape here encountered. The differences noted MIOCENE MARINE MAMMALS 55 while examining this specimen are not of sufficient importance to justify the application of a new name. Presumably, these fragments resemble Sawrodelphis acutiro- stratus Rovereto” in a general way. One can not make direct @0e0 eA A A OOO? —— = Fig. 9. ? Macrodelphinus kelloggi. x 2/5. A, B. Ventral view. C-E. Cross sections. comparisons between the anterior fragments of the mandibles in Rovereto’s type and these rostral fragments, which, furthermore, are located farther behind the anterior extremity. The anterior fragment shows 19 alveoli in the left side of the rostrum in a space of 208 mm., an average of 10.9 mm. for an alveolus plus septum; and the right side shows 20 alveoli in a space of 216 mm., an average of 10.8 mm. The greatest diameter of an 28. Rovereto, C.—Nuevas investigaciones sobre los delfines longirrostros del Miocene del Paranda (Reptblica Argentina). Anales del Mus. Nac. Hist. Nat. Buenos Aires, Tomo XXVII, p. 146, pl. 3, figs. 1, 2, 1915. 56 PEABODY MUSEUM OF NATURAL HISTORY alveolus alone varies from 8.8 mm. to 10.5 mm. The tendency for the alveolus to assume an elliptical form, mentioned by Rovereto, is seen in this specimen. But this specimen also shows alveoli which are circular adjoining those which are elliptical, and the writer is inclined to believe that this character is of doubtful value as an aid in determining the generic position of the specimen here described. The alveoli and teeth of Saurodelphis acutiro- stratus are separated by varying intervals at different places on the mandible. The measurements not given in Rovereto’s table were computed from the photographs and may not check pre- cisely with the true measurements. The right side shows 14 alveoli in a distance of 302 mm., an average of 21.6 mm. for 1 alveolus plus septum. But the 5 anterior alveoli plus septa occupy a space of 159.5 mm., an average of 32 mm. per alveolus plus septum, the 4 center ones average 17.5 mm., and the 5 posterior ones, 13.4 mm. The depth of the rostrum of No. 13412 at the point of the anterior break is 33 mm., and the anterior break of Rovereto’s specimen measures 21.4 mm., as nearly as can be ascertained from the photographs. The writer is not inclined to allocate the rostral fragments here described to Sawro- delphis acutirostratus. From the standpoint of regularity of size of tooth socket, the rostral fragment which received the name Ischyrorhynchus vanbenedent Ameghino™ *° more closely resem- bles No. 13412 than any other description or figure found. But in I. vanbenedeni the size of the alveoli vary from 11 mm. to 18 mm. in the short fragment (100 mm.). The width of the septa between alveoli reaches 7.6 mm., while in specimen No. 13412 the maximum width of a septum is 3 mm. It is probable that this South American Pliocene genus and No. 13412 are not the same. The length of the more distal fragment is 225 mm. and con- 29. Ameghino, F.—Caracteres diagnosticés decincuenta especies nuevas de mamiferos fésiles Argentinos. Revista Argentina de Hist. Nat., Tomo I, pp. 163-165, figs. 71-72, 1891. 30. Cabrera, A.—Cetdceos fésiles del Museo de La Plata. Revista del Museo de La Plata, Tomo XXIX (Tercera serie, Tomo V), p. 403, 1926. MIOCENE MARINE MAMMALS 57 tains 19 well-preserved alveoli on the left side and 20 on the right. Counting forward from the posterior end of the fragment, left alveolus number 13 contains a tooth broken off below the crown. No teeth are preserved on the right side. The posterior fragment has a length of 150 mm., consisting of part of the sym- physis of the rostrum, the left half of the jaw showing 9 alveoli in a space of 97 mm. and the right, 11 in a space of 139 mm. An interesting character of both fragments is the occurrence of well-defined vascular grooves running lengthwise of the rostrum in a position which seems to correspond, on the posterior frag- ment, with the contact of the premaxilla and maxilla. The prox- imal end of the more posterior fragment shows a deep, narrow groove, in the position of the superior borders of the maxillae, which appears to separate the lateral part of the rostrum into two divisions believed to be the maxilla and premaxilla, as was the situation in Macrodelphinus kelloggi (individual 2). Toward the anterior end the separation is not visible, and the groove MErAsurREMENTS oF Rostrat FRAGMENTS Anterior fragment Naximum length of anterior fragment: 22 2))) 5)... sss sc oe 225 Metivside nas U9alveols in space.Of 2. 2055, nnn tio eles Se els be 208 migutsside has 20 alveoli im space: Of o/s 55.5 <0 e0 cj<'e secs 216 Maximum diameter of tooth root in 18th socket of left side (counting forward from the most posterior one)........ 9.7 Minimum (transverse) diameter of same tooth root......... 6.0 Werticaladepth of rostrum at. anterior break......5. .). 0%. 0s/+-'. 33 Vertical depth of rostrum at posterior break............... 42 Maximum width of rostrum at anterior break............. 21 Maximum width of rostrum at posterior break............. 28.5 Posterior fragment Menethyor Posterior TrAgMENt. . ..p.,0.0s els tye oes laces = sees 150 Mei sile-has S/alveoli in’space Ofc... tacos ss cleo e wae ceo 97 nee side hasald ‘alveoli in’space GLP Ii f.6.o st. aio em. oeleete 139 Maximum depth of right side of rostrum at anterior break.... 43 Maximum depth of right side of rostrum at posterior break... 45.5 58 PEABODY MUSEUM OF NATURAL HISTORY becomes wide and shallow, showing no visible trace of separation into two parts. The grooves continue, with some irregularities of direction, to the anterior end of the distal fragment. The groove on the right side shows two foramina in the anterior frag- ment, with their posterior edges separated by an interval of 58 mm. At the level of the anterior one of these on the right side of the rostrum, is a slight swelling carrying a small oblique ridge which may represent an injury or some pathologic condition. Judging by the cross sections of the breaks, the interval between these two fragments is about 100 mm. on the left side. Genus ACRODELPHIS Abel Acrodelphis bakersfieldensis,** new species Figs. 10-11 Holotype.—Cat. No. 18406 Y. P. M. The skull is incomplete, lacking the distal portion of the ros- trum, part of the left supraorbital process of the frontal, the right zygoma, right exoccipital, right occipital condyle, and most of the supraoccipital. Type locality and horizon—The same as for the holotype of Macrodelphinus kelloggi. Skull Dorsal view.—The dorsal surface of the skull consists princi- pally of the maxillaries, premaxillaries, frontals, and nasals. The vertex of the skull, formed by the frontals and nasals, is flat and somewhat wider than long. The nasals rise abruptly from the frontals to form a sharp crest at their anterior edge. The pre- maxillaries are extended back to a level with the anterior edge of the nasals, in which they differ from Argyrocetus joaquinensis (Kellogg, R., footnote 11). The line of demarcation separating the lacrimal, the maxillary, and the supraorbital process of the frontal, ventrally, is a shallow but broad furrow. On the rostrum 31. Named for Bakersfield, California. MIOCENE MARINE MAMMALS 59 the anterior part of the maxillary descends to a straight, sharp edge. In the central portion of the maxillary a ridge begins its development 90 mm. in front of the maxillary notch and becomes fairly prominent and somewhat rounded as it approaches the maxillary notch. A large maxillary foramen occurs at the level of the maxillary notch, and a second, smaller one occurs 20 mm. behind the maxillary notch and in line with it. The maxillary gives the appearance of having overspread the supraorbital process of the frontal irregularly, reaching nearly to the outside edge poste- riorly and about half that distance at the suture of the lacrimal and supraorbital process. At the posterior end of the maxillary, a sharp ridge is formed at the junction of the maxillary with the nasals and frontals. This ridge disappears at the posterior end of the frontal but is recurved on itself slightly, forming a concavity, throughout the length of the nasal. Anteriorly, the premaxil- laries are rounded and thick on the outer edges. The inner edge becomes thinner posteriorly, particularly so at its contact with the mesethmoid. Two small grooves arise on the inner half of the premaxillary 45 mm. in front of the maxillary notch. The outer one deepens posteriorly and extends into the premaxillary foramen, the anterior edge of which is located just behind a transverse line from the maxillary notch, and continues pos- teriorly, to give the impression of separating the premaxillary into two parts, one of which, a broad, slightly concave, inner part, is raised increasingly above a narrowing outer edge. Just behind the premaxillary foramina, the premaxillaries ascend quite sharply, become broad where they form the outer borders of the nares, and reach back to touch the outer anterior edges of the nasals. The inner edges of the premaxillaries are in con- tact at a distance of 120 mm. in front of the maxillary notch. From this point of contact they diverge posteriorly for a distance of 94 mm. and then converge gradually. The nasals, which are in their natural positions, rise abruptly from the anterior edges of the frontals, overriding the dorsal end of the mesethmoid. On both sides there appears to be clear separation of the nasals from the maxillaries and premaxillaries ; but stylolite-like sutures unite 60 PEABODY MUSEUM OF NATURAL HISTORY Fig. 10. Acrodelphis bakers fieldensis (holotype), dorsal view. x 2/5. For explanation of lettering, see Fig. 1. MIOCENE MARINE MAMMALS 61 the nasals with the frontals. The frontals are flat and have their greatest length on the outside edges adjoining the maxillae. The posterior part of the left frontal is raised into a ridge just anterior to its junction with the supraorbital process. The right frontal is flat throughout. In both frontals, the greatest lateral extensions occur at the anterior and posterior edges. The supra- occipital is preserved only along its anterior edge. Along its medial line there is an abrupt descent from the union with the frontals, and a basin-like depression of small proportions is formed. 'The whole supraoccipital drops away from its anterior margin posteriorly in a sudden descent, forming ridges where the maxillae meet the supraoccipital. The left premaxilla shows two foramina instead of one as on the right, separated by a ridge some 3 mm. in width. The shape of each narial passage is that of a high, narrow triangle with an arc as base. The well-developed mesethmoid separates the narial passages. The internal edge of each premaxilla is notched near the anterior limit of the choanae with an apparently natural and abrupt posterior widening (about 3 mm.) of the narial area. All the bones of the dorsal part of the skull are relatively heavy as compared with the modern dolphin. Lateral view.—This view is marked by the stoutness of the bones forming the rostrum, the evenness of the rostral thickness and the gradual changes in deflection, the backward projection of the pterygoids, and the stoutness of the supraoccipital. The nasals form the highest part of the skull. The maxilla loses its rounded outline and becomes depressed about 75 mm. in front of the maxillary notches and, at the position of the palatine, widens and becomes thinner. Only the antero-superior end of the jugal is preserved, and its separation from the lacrimal is not plain. The separation of the lacrimal from the supraorbital and the maxillary is indicated by closed sutures; this condition differs from that of Argyrocetus in having a much wider part of the supraorbital and the lacrimal exposed instead of being covered by the overreaching of the maxillary. It appears that the maxil- lary crowding came from a posterior direction, since the posterior 62 PEABODY MUSEUM OF NATURAL HISTORY end of the supraorbital is much more widely covered than is the anterior part. The extreme posterior end of the right maxillary is broken and lacking, and the posterior tip of the supraorbital is broken away. The supraorbital shows only a slight curvature in a vertical direction, with the heaviest portions at the anterior and posterior edges and with the middle part comparatively thin. The optic canal is deep, rounded, and fairly well preserved for a distance of 32 mm. from the base of the supraorbital process. The palatines are lacking, but their shape and size may be judged from the vacuities which remain. ‘The anterior edge of the pala- q lveolar row Fig. 11. Acrodelphis bakers fieldensis (holotype), lateral view. x 2/5. For explanation of lettering, see Fig. 1. tine vacuities begins almost opposite the maxillary notch as a rounded point and extends in a posterior direction for a distance of 27 mm., where it attains a width of 27 mm., thus being repre- sented in the lateral view as an equilateral, triangular depression. If the palatines were not of a diverging type but followed the suture-like depressions in the maxillaries, they extended a distance of 50 mm. in front of the notches at the anterior edges of the pterygoids. The lacrimal is rounded anteriorly and fits against the maxillary notch and is drawn out and thinned where it attaches to the jugal. The posterior edge is in the shape of a ridge, slightly rounded and higher at its outside edge; and its attachment to the supraorbital process seems to be a straight MIOCENE MARINE MAMMALS 63 suture. The basal anterior part of the jugal has a ridge-like shape, and its styliform process is partially preserved as a thin, sharp-edged bone. The posterior parts of the pterygoids are partially preserved, but the hamular processes are lacking. The pterygoids are separated from the posterior edges of the palatine depressions by a distance of 10 mm. The left zygomatic process of the squamosal has considerable dorso-ventral thickness inter- nally and gradually tapers to a thin external edge. The process is strongly curved, short, and straight transversely at the pos- terior edge. The whole curves upward on the dorsal side. This process is much shorter and thinner than that of Allodelphis pratti. Between the posterior end of the zygoma and the exoc- cipital are two large depressions in the joining bone. Posterior view.—The left occipital condyle is wider dorsally than ventrally and has its maximum width slightly above the transverse center line. The neck is continuous around the con- dyle and shallower on the dorsal side than elsewhere. The dorsal edge of the exoccipital forms a sinuous crest. Ventral view.—The anterior ends of the maxillaries are rounded on the outside portions but on the interior edges descend in almost a straight line to meet the vomer, which projects into the space between the maxillaries to a height of 4 mm. over a distance of 47 mm. The sharp ridge of the vomer becomes rounded and flattened in a posterior direction 100 mm. in front of the maxillary notches. The maxillaries meet 50 mm. in front of the anterior end of the palatine depressions. These palatine depressions extend a few millimeters in front of a transverse line from the maxillary notch. The left narial opening is somewhat larger than the right. The pterygoids extend down from the crest to the optic canal, where they are turned at a reéntrant angle. The posterior extremities are broken away. The internal dorsal aspect of the brain case is visible on the right side. The brain case is somewhat narrower anteriorly than posteriorly. The olfactory foramina are notice- ably large, the right one being about twice as large as the left. A strong medial crest, having a height of 13 mm., descends from the roof of the brain case and continues forward as far as the G4 PEABODY MUSEUM OF NATURAL HISTORY MEASUREMENTS OF SKULL Total length ‘as preserved «3. 3 3c6.0t oo ae oe ee Transverse semi-diameter of skull at level of posterior edges of premaxillary foramina across supraorbital processes of frontals/'(zight half) oe. eee as selves ict cce deinen Greatest vertical depth of skull at level of anterior borders of MaPiall spassageEs} slice) he = apredoied ee 20 etek dere eee eee Greatest vertical depth of rostrum at level of maxillary notches Greatest vertical depth of rostrum at broken extremity (141 mm.3n front of maxillary notches). «2-20.01 a oe ete Greatest distance between outside margins of premaxillaries at level of anterior border of narial passages.......... Greatest breadth of left premaxillary at level of anterior bor- der ‘of, marital ‘jpassagesi.t<. J 0% oiqe seuss p oles Seen Greatest breadth of left premaxillary at level of maxillary PROUD, Sos is Siete ape ensy ais heksc oie eb iniss wee eae eye nee ei eee Distance between inner margins of premaxillaries at level of ANtEPIOL MAPPING Of. NASaIS).. . .% 6c4 elcsaii ee eee Maximum transverse diameter of right premaxillary at level of narial passapes:..:/01.). oineu Med sisi: cretels kts ae ere Breadth of rostrum at level of maxillary notches............ Greatest antero-posterior diameter of left nasal along suture. . Greatest antero-posterior diameter of right supraorbital process of: fromtals s «6 5.0 6.¢ wists: sise = <6 shou nee Transverse diameter of left nasal at anterior end........... Width of brain case at level of olfactory foramina.......... Least distance between inner margins of maxillaries on vertex OF Skat eicus pds) Saud Byoe sas, sacs Eee oo eee Distance from level of anterior edges of nasals to anterior edge of ‘supraoccipital medially” ... «3... <<): s0.6= ope-mne Maximum transverse diameter of combined nasals.......... Maximum transverse diameter of right nasal.............. Maximum antero-posterior diameter of right nasal......... Maximum antero-posterior diameter of frontal along median Sere eS 55s n,n, sete seb sueuelekeuaas hcuses vets Stok ane Transverse width across pterygoids at level of post-orbital process Of -Trontal’s 2:0. ss. as we cee Rie eats plete le ie eee Maximum width of right supraorbital process of frontal at level of premaxillary foramen: 2... 42.2006 .450 Abeer The left maxilla has 20 alveoli in a distance of 109 mm. counting forward from the posterior edge of the posterior alveolus to the anterior edge of last alveolus measured. 260 71.3 60.8 46.2 29.5 64.7 26.6 20.8 24.6 MIOCENE MARINE MAMMALS 65 The right maxilla has 20 alveoli in a distance of 108 mm. counting forward from the posterior edge of the posterior alveolus to the anterior edge of the last anterior alveolus measured. Maximum antero-posterior length of zygoma (left)......... 60 Maximum transverse width of zygoma (left).............. 29 Maximum dorso-ventral diameter of left occipital condyle.... 35 Maximum transverse width of condyle.................+ 23.6 Transverse diameter of skull between outer surfaces of zygo- MPR CME OCESSES) o- chevete ove (el oyayal ake eset sain) =) fehl) aie)ie 111s ole = = NGG fe olfactory foramina, where it descends abruptly to them. The left half of the basioccipital is preserved for its full length. The posterior extension of the vomer is considerably thicker, where it overlaps the basioccipital, than in the modern dolphins. The side of the basioccipital is steep and descends to the limit of the exoccipital. The ventral, internal curvature of the zygomatic process is clearly observed in this view. The lower, anterior division of the squamosal (falciform process) is much wider than in the modern Tursiops truncatus. The exoccipital is stout. Between it and the posterior wall of the basioccipital is the wide notch for the jugular leash, and at the top of the notch appears the hypoglossal foramen. The tympano-periotic recess is longer than wide, straight internally, and rounded externally. The internal carotid foramen may be seen emerging on the dorsal side of the basioccipital. Its ventral point of entrance is on the external side of the basioccipital. The foramen for the man- dibular branch of the trigeminal nerve is irregular in outline, being wider anteriorly than posteriorly. Teeth—The right maxilla shows 20 alveoli in a length of 108 mm. The tenth one, counting forward from the posterior alve- olus, has, in place, a broken tooth whose width is 3 mm. The left maxilla has 20 alveoli in a length of 109 mm. The alveoli are quite distinct on the left maxilla but are somewhat worn on the right one. The tooth which is present is not sufficiently complete to describe. Remarks.—Although the diagnostic generic characters are 66 PEABODY MUSEUM OF NATURAL HISTORY found in the mandibles, the identification of the skull of A. scheyn- ensis by Abel** has made some of the cranial peculiarities available for comparison. The mutual relations of the bones of the skull, as brought about by the process of telescoping, are similar to Acrodelphis, especially the relations of frontals to nasals and maxillae, the relatively large size of the nasals and their shape, the degree of lateral compression of the vertex of the skull, and the posterior prolongation of the premaxillae. These characters are common to A. bakersfieldensis and A. scheynensis du Bus (Abel, O., p. 137). In specific characters the skull of 4. bak- ersfieldensis differs from A. scheynensis in that the premaxil- laries of the former attain a greater height, the rostrum is wider at the level of the maxillary notches, and the supraoccipital is concave at its superior border while that of the latter is rounded as in Phocaena. The mesethmoid is more elevated in A. bakers- fieldensis than in A. scheynensis. Longhi** gives the measure- ments of the teeth of A. ombonii. In A. bakersfieldensis only the roots of two teeth are preserved, and diameters of alveoli and roots of teeth are generally different. However, it would seem that the teeth of A. omboni are slightly larger than those of A. bakersfieldensis, judging by the size of the alveoli, which vary in A. ombonit from 10 mm., the diameter in the anterior alveoli, to 4 mm., the diameter in the posterior alveoli. Of the twenty alveoli of the left maxillary of A. bakersfieldensis, the hindermost one is 8 mm., the twentieth is 4 mm., and the largest of the twenty is 5 mm. in diameter. Longhi, unfortunately, fails to give the degree of enlargement of his photographs. 'The two teeth of A. bakersfieldensis are incomplete, and the specimen can not, therefore, be compared with A. denticulatus,** founded on three teeth. A. bakersfieldensis is the first species of Acrodelphis which 32. Abel, O.—Les odontocétes du Boldérien (Miocene Supérieur) d’Anvers, Mém. Mus. Roy. d’Hist. Nat. Belgique, Tome III, pp. 130-139, 1905. 33. Longhi, P.—Sopra i resti di un cranio di Champsodelphis fossile sco- perto nella molassa Miocenia del Bellunese. Atti. Soc. Veneto-Trent. Sci., 2d ser., vol. iii, pp. 323-381, pls. i-iii, 1897. 34. Probst, J., 1886, see Abel, O. Op. cit., p. 135. MIOCENE MARINE MAMMALS 67 has been recorded from the Pacific Coast of the Americas. True*® says, “. . . it is probable that some of the American species [of Odontoceti] are referable to the European genera . . . Acro- delphis .. . ,” and states that he has found in Maryland ver- tebrae belonging to Acrodelphis. Skeletal parts found with this skull and referred to it tenta- tively are the fourth and sixth cervical vertebrae and the left humerus. The skull and skeletal parts were discovered by Mr. Charles A. Pratt and excavated by Mr. Pratt, Mr. T. V. Little, and the writer. Cervical Vertebrae Two cervical vertebrae, the fourth and sixth, found with this specimen are referred to it. Neither is complete. The out- standing character is the thinness of the centra. Fourth cervical—This cervical lacks the top of the neural arch, the right posterior articular process, and most of the right lower transverse process. The centrum has the outline of an upright shield with top, bottom, and sides deeply concave within the facial ridges, probably resulting from the process of short- ening. The left posterior articular facet is sub-rectangular in outline, elongated posteriorly, nearly horizontal in position, and large compared with its supporting pedicle. The left upper transverse process descends from the side of the neural arch to unite with the lower transverse process, forming a broad, thin sheet of bone between the processes and entirely enclosing a large, ovoid arterial canal. The left lower transverse process is well developed, with a wide flange on its ventral border. It is directed obliquely backward. The process is moderately long. Sixth cervical—The centrum of this cervical is noticeably thicker than that of the fourth, less shield-like, and more nearly rectangular in outline. The right lower transverse process is lacking, as are, also, the left pedicle and superior parts of the 35. True, F. W.—On the correlation of North American and European genera of fossil cetaceans. Proc. Internat. Zool. Cong., vol. VII, p. 781, Boston, 1907. 68 PEABODY MUSEUM OF NATURAL HISTORY neural arch. The left lower transverse process is directed obliquely backward at a much lower angle than that of the fourth. The process is blunt anteriorly and thin posteriorly. Near the centrum, it bears a projection which marks the external boundary of the arterial canal. This canal is much larger than that of the fourth and probably was not enclosed on the external border. The right posterior articular facet is curved internally at its posterior border and is wider anteriorly than posteriorly. MEASUREMENTS OF CERVICAL VERTEBRAE Ath 6th Greatest breadth. of neural ‘camal.... 2.2362 33.2 21 Median height of anterior face of centrum....... 31 31.5 Maximum breadth of anterior face of centrum.... 39 35 Length of centrum minus facial discs............ 10 x Length of centrum with one facial disc.......... og 13.5 Distance across vertebra between exterior edges of posterior articular facets <2... 2s cste aie oe cima 54 62.8 Width of posterior articular facet (left, 4th; right, GE) 8s Eo a enhetis s aes ate ee oh o's lara ieereeee 10 10.3 Length of posterior articular facet (left, 4th; right, GED) hea ees Ae AWRY te cee oe eee eae 11 13 Greatest diameter! of arterial canal. < o2u.7-eeciae 12.3 20 Minimum diameter of left rudiment of upper trans- WETSC PEOCESS fae, mica ore sei evelmyele ouesi enero site eke ae 3.9 x Length of left lower transverse process......... 33 34.5 Left Humerus The humerus is complete and well preserved. The internal border is concave, but less strongly so than that of Eurhino- delphis bossi. 'The anterior edge is blunt and strongly convex for the greater part of its length, reaching its maximum thickness at the level of the infraspinous fossa, where the deltoid process is not clearly delimited from the deltoid ridge. The oval head is set off from the shaft by an unconstricted neck which disap- pears on the dorsal side. The posterior tuberosity is sharply separated from the anterior by a steep face, less clearly sepa- MIOCENE MARINE MAMMALS 69 rated from the head, slightly convex, and pitted with small pits. The anterior tuberosity is set below the posterior. The bicipital groove is shallow except at the posterior extremity. Posteriorly, the whole bone is broad and flattened, including the head. The capitulum bears an antero-posterior groove into which the internal and external faces slope. This groove passes into the trochlea, which continues in a dorsal direction along the posterior edge of the humerus to form a flat facet, over the full width of the bone, for the articulation of the proximal part of the olecranon process of the ulna. A transverse ridge separates the capitulum and trochlea. MeEasurREMENTs oF Lert Humerus Greatest length, proximal end of greater tuberosity to ridge on distalvend, alone internal border. 2.22.5... «5.2 eee sss 94.4 Maximum extero-internal diameter of distal end............. 24 Maximum antero-posterior diameter of distal end............ 35 Greatest length of deltoid fossa’: 5 ..6.565 sis. o eis eis 6 oes ae ss 24 Srearest widen of deltoid: fossa. 6. 4.6 o cise a eae sn oe ecta a ope we 14 ‘creavestudiameter Of Meads ioe fai. cio are wh sicie ce seni aiele «© 34 Measutdiamecter (Of Head cs 6 cis crs alam she ele, « eels lolcv ane ® lero eres 6s 30 Acrodelphis bakersfieldensis, new species (Individual 2) Fig. 12 Referred specimen.—Cat. No. 18410 Y. P. M. This specimen consists of the incomplete facial portion of a skull in which the distal part of the rostrum is lacking; the supraorbital processes of the frontals, with their overlapping maxillaries, are broken off approximately at the maxillary notches; the internal edges of the premaxillae are broken; the posterior edges of the maxillae and premaxillae have suffered erosion, as have all the bones of the vertex of the skull; and the entire occipital region is lacking. This specimen was discovered and collected by the writer in the spring of 1930. 70 PEABODY MUSEUM OF NATURAL HISTORY Locality —_N.W. 14 of Section 4, T. 28 S., R. 29 E., M. D. B. & M., near the N-S center line of the section. Horizon.—Near the contact between the Pyramid Hills Sand and the “Walker” formation. Skull Dorsal view—The premaxillae, at the anterior, broken end of the rostrum, are thick and rounded dorsally and lie quite close against and on top of the inner edges of the maxillae. The pre- maxillae are rapidly converging. The mesorostral gutter is deep Fig. 12. Acrodelphis bakersfieldensis (individual 2), dorsal view. x 2/5. For explanation of lettering, see Fig. 1. and large. A small, narrow groove originates 25 mm. in front of the anterior edge of the premaxillary foramen and runs directly back into the foramen, then continues in a posterior direction, sharply differentiating the premaxilla into two parts, a broad, raised, interior face and a narrow, outer border. The premaxillae are heavy throughout and reach posteriorly to a point approximately 8 mm. in front of the anterior edges of the MIOCENE MARINE MAMMALS 71 nasals. At the premaxillary foramina, the premaxillae slope transversely upward to the mesethmoid, which is thick wher- ever preserved. At a distance of about 24 mm. behind the maxillary notches, the premaxillae rapidly diverge, until at their most posterior extension, they are separated by an interval of 33 mm. The maxillae, at the anterior end of the specimen, slope steeply away from the medial line. A large maxillary foramen has its posterior edge on a level with the maxillary notches and is located in the center of the maxilla. A second maxillary fora- men lies posterior to the first one on an oblique line. The distance between the two foramina is 10 mm. on the left premaxilla and 13 mm. on the right one. It is plain that the maxilla did not reach to the outside border of the right supraorbital process. The maxilla appears to be much thicker at the posterior end of the supraorbital process than at the anterior end, a circumstance which may be evidence that the thrust which caused the spreading of the maxilla came from behind. The nasals are short in an antero-posterior direction and may be partially eroded at their anterior edges. The right one is slightly larger than the left. The frontals slope away from the medial line, giving the apex of the skull a slightly rounded appearance. The frontals slope gradually upward from their posterior edges, and no abrupt change of slope is noticeable until the anterior edges of the nasals are reached. The mesethmoid is pierced by two large, crescent- shaped olfactory foramina. Ventral view—The alveoli have been eroded. The alveolar gutter begins 24 mm. in front of the maxillary notch. The ventral side of the dorsal edge of the maxilla projects well beyond its inferior portion. The anterior end of the ventral side of the maxilla is narrow but widens rapidly in a posterior direction, and the two maxillae meet in a median line slightly in front of the palatine vacuities. The parts of the lacrimal, as preserved, are very small and can not be described. The infraorbital foramina are large. The right one is rounded; the left one, partly broken. Judging by the palatine sutures on the maxillaries and the medial suture, the palatines were closely appressed. The pterygoids are 72 PEABODY MUSEUM OF NATURAL HISTORY preserved only on the interior of the narial openings. The brain case presents a circular appearance, with two large concave depressions on the sides. The olfactory foramina occupy a posi- tion nearly central in the preserved portion of the brain case. Above the olfactory foramina is a blunt, triangular prominence, MEASUREMENTS OF SKULL ‘Eotal length..as preserved... 4:4 js os erst ais pois oo hey eee Transverse diameter of skull across preorbital angles of supra- orbital processes of frontals as preserved.............. Greatest vertical depth of skull at level of anterior borders of NATAL PASSAGES co Ake eee ae A he ae ee tae Greatest vertical depth of rostrum at level of maxillary notch. . Greatest vertical depth of rostrum at broken extremity (70 mm.. infront of maxillary notches). << <.2.2< «.c0.-— «eee Greatest distance between outside margins of premaxillaries at level of anterior border of narial passages............. Greatest breadth of left premaxillary at level of anterior border ‘of ‘arial passages: oe. 25's a oeteret ates oo ene eee Greatest breadth of left premaxillary at level of maxillary Moths 2 5.x s'srvs tag llstee seid < ea sheeen aur oer e eee Distance between inner margins of premaxillaries at level of anterior margins, of nasals.). 207.0)... ono. +p ae eee Maximum transverse diameter of right premaxillary at level of Narial “passaves’ 2600. j-ic ss eas 5 Sete eee eee ee ee Least distance between inner margins of maxillaries on vertex ye) id i re AE ee Aire n Aa Ie boo oS Width of right premaxilla 60 mm. in front of maxillary notch Breadth of rostrum at level of maxillary notches............ Antero-posterior diameter of left nasal along medial suture... Transverse diameter of left nasal, anteriorly............... Width of brain case across olfactory foramina.............. Distance from level of anterior edges of nasals to anterior edge of ssupraoccipital ‘medially . 575 .).1a6:)s ieee) Selene ae Maximum transverse diameter of right nasal.............. Maximum transverse diameter of combined nasals.......... Maximum antero-posterior diameter of right nasal.......... Maximum antero-posterior diameter of frontal along median sutaral’ Vitve 2050.7. 3 Fa 'n'. f. 2s ainda e = tetade ne ora eo meehte eee Width of posterior opening of left olfactory foramen........ Length of posterior opening of left olfactory foramen....... 12.5 MIOCENE MARINE MAMMALS 73 apparently formed by an inferior posterior projection of the frontals. The nasal apertures are large and nearly circular. The large size of the olfactory foramina is an outstanding char- acter within the brain case. Remarks.—This skull is tentatively referred to Acrodelphis on the basis of the similarity of the general relations of the bones of the dorsal side of the skull to those of Acrodelphis scheynensis. The absence of teeth, mandibles, and skeletal parts makes a definite allocation impossible. The large size of the nasals, pos- terior position of the premaxillaries, gradual slope of the facial region, and small size of the skull are the chief characters relating this specimen to Acrodelphis. This skull differs from Acrodelphis scheynensis du Bus (a fragmentary specimen) in the length of the external border of the nasals, that of A. scheynensis meas- uring 13.5 mm., while that of 4. bakersfieldensis (individual 2) measures only 9 mm. Also, the anterior border of the left nasal of A. scheynensis measures 22.8 mm., and that of A. bakersfield- ensis (individual 2) reaches only 19 mm. This apparent differ- ence in the nasals may be the result of the erosion of the apex of the skull of 4. bakersfieldensis (individual 2). Other apparent differences between the bones of the skulls, such as the width of the maxilla at the maxillary notch, may be accounted for by the position of the skull of A. scheynensis when photographed. 'These several apparent differences between the holotype and individual 2 of A. bakersfieldensis are of less importance than the following, namely: in individual 2 the posterior extremities of the premaxillae end in front of the anterior border of the nasals, and in the holo- type they end at the anterior edge of the nasals. In view of the similarities of the skulls, this one point of difference is not now considered sufficient to remove individual 2 from the specific desig- nation. The greater height of the presphenoid in individual 2, with its consequent elevation of the internal edges of the pre- maxillae, is an age variation, as is shown by a study of a series of modern dolphins, the high presphenoid being a character of maturity. The holotype is a somewhat larger specimen than individual 2. 74 PEABODY MUSEUM OF NATURAL HISTORY Acrodelphis bakers fieldensis (Individual 3) Figs. 13-14 Referred specimen.—Cat. No. 13411 Y. P. M. This specimen consists of the portion of the rostrum lying just anterior to the narial openings and made up of the premaxillae and maxillae. The right maxillary has split, the palatal portion being forced inward, exposing the alveolar gutter. The left maxillary has been pushed out of position, exposing the ventral surface of the vomer. The left half of the rostral fragment is, thus, apparently normal, while the right half is certainly distorted. Locality and horizon.—Southern part of Section 12, T. 26 S., R. 28 E., M. D. B. & M., from the pit which yielded the holotype of Macrodelphinus kelloggi. Rostral Fragment Dorsal view.—The premaxillae meet on the mid-line, 107 mm. in front of the premaxillary foramen. The shape of the pre- maxilla, in cross section, at the anterior end of this rostral frag- ment is that of a half crescent, with the thin extension on the interior side. ‘The outside edge rounds over gradually to its point of contact with the maxilla and then becomes nearly ver- tical. The whole premaxilla fits into a groove of the maxilla. In a posterior direction, the shelf-like inner portion of the premaxilla becomes wider, and the main outer portion becomes narrower and thinner until, at the premaxillary foramen, the latter constitutes only a narrow depressed border to the raised and widened, con- cave, inner portion. A shallow, irregular groove runs anteriorly from the premaxillary foramen to the hinder broken edge of the premaxilla, a distance of 37 mm. On the anterior portion of this rostral fragment, the maxillae show a gradual slope in a transverse direction from the outer margin of the premaxilla. A groove has its origin a distance of 77 mm. in front of the posterior edge of the maxillary foramen and becomes gradually MIOCENE MARINE MAMMALS 75 deeper and slightly narrower as it passes into the maxillary foramen. The minimum oblique distance between the premaxil- lary and maxillary foramina is 13 mm. The exterior edge of the maxilla forms a shield above the alveolar gutter. The distance from the posterior end of the maxillary foramen to a transverse line drawn from the posterior end of the alveolar gutter is 21 mm. Ventral view.—The shelf of the maxillary overhanging the alveolar gutter is well shown on the right side in this view. Except Fig. 13. Acrodelphis bakers fieldensis (individual 3), dorsal view. x 2/5. Fig. 14. Acrodelphis bakers fieldensis (individual 3), lateral view. x 2/5. at the posterior end, the alveoli are eroded. Where preserved, the alveoli are seen to curve downward and inward posteriorly. An alveolus shows a length of 8 mm. It appears that there are 4 alveoli on the right maxilla in a distance of 18 mm. near the posterior end of the alveolar groove. Other septa of the alveoli are too much eroded to be counted with accuracy. The maxilla rounds underneath as it enlarges and unites with its counterpart from the opposite side to furnish the floor of the mesorostral gutter, which is wide, open, and rounded and rapidly tapers to a small opening at the anterior end of the specimen. The anterior 76 PEABODY MUSEUM OF NATURAL HISTORY extent of the palatines can be determined by the positions of their sutures, which are marked on the maxillaries. At the posterior end of each palatine vacuity is a nearly vertical groove which was walled by the palatine and roofed by the outer pterygoid, when these bones were present. MEASUREMENTs OF RostRAL FRAGMENT Kength of, rostrum ‘ag preserved © 0) ehi2 @ cela tare ote ere aie 180 Width of rostrum at level of left premaxillary foramen....... 79 Depth of rostrum at level of posterior end of palatine depres- Eth Mee ao re Sys One Aig ae Sor ota SoA Sac 55 Posterior end of left alveolar groove has 6 alveoli in a dis- bance OF) sats i ant ecra hc e tors where eusivtw cohen oleae eee 27.3 Transverse width of left maxilla at level of maxillary fora- Hite) | Bec eiCe a a NOnG Pune ho OIC SOK SE DoS os 20 Transverse width of left premaxilla at same level......... 19 MIODELPHIS,”* new genus Genotype.—Miodelphis californicus, new species. Diagnosis.—The skull of this dolphin is characterized by the close approximation of the maxillae at their posterior extremities, the oblique truncation of the maxilla above the temporal fossa, the large, rectangular exposures of the frontals on the vertex, and the small size of the occipital condyles. Miodelphis californicus, new species Figs. 15-16 Holotype.—Cat. No. 13407 Y. P. M. The skull is incomplete, lacking the rostrum from the maxillary notches forward, the nasals, the right supraorbital process of the frontal, most of the left zygomatic process of the squamosal, and most of the pterygoids. This specimen was discovered by the writer in the spring of 1930. Two hyoid bones and two vertebrae found with tis specimen are tentatively referred to it. 36. Mio(cene) + ded¢is, dolphin. MIOCENE MARINE MAMMALS Tk Type locality—S. W. 14 of Section 12, T. 26 S., R. 28 E., M. D. B. & M., about 100 yards northeast of the location of Macrodelphinus kelloggi (holotype). Horizon.—Pyramid Hills Sand at approximately the same level as M. kelloggi (holotype). Skull Dorsal view—The premaxillae end, posteriorly, opposite the nasals at a point 10 mm. in front of the anterior edge of the frontals. The external border of the premaxilla is smooth and == ne spe aaae® ° Z Fig. 15. Miodelphis californicus (holotype), dorsal view. x 2/5. For explanation of lettering, see Fig. 1. flat, measuring 8.5 mm. in width on a level with the maxillary notch. The border quickly disappears in a posterior direction, and accordingly, the maxilla is then undifferentiated between external and internal parts (cf. Allodelphis, Macrodelphinus, Doliodelphis, and Acrodelphis bakersfieldensis). The internal edges of the premaxillae are not in contact in this specimen. Their expansion horizontally on a level with the narial passages is less than that shown by other fossil dolphins from this region. 78 PEABODY MUSEUM OF NATURAL HISTORY On a level with the maxillary notch is a small premaxillary foramen lying at the junction of the two parts of the premaxilla. The maxillae are unusually broad and closely approximated at the vertex. The posterior external border, from the frontal to the supraorbital process, is a straight edge which gives the appearance of oblique truncation of both maxilla and frontal. The maxilla does not overspread the supraorbital process com- pletely but leaves a border of several millimeters in width throughout the length of this process. The maxilla is thicker at Fig. 16. Miodelphis californicus (holotype), lateral view. x 25. For explanation of lettering, see Fig. 1. the anterior than at the posterior border of the supraorbital process of the frontal. Two foramina occur in the maxilla. One is on a level with the center of the supraorbital process and 6 mm. from the premaxillary boundary; the other occurs 44.5 mm. behind the first one. The left maxilla shows erosion at its pos- terior extremity, where it overlaps the frontal. The nasals are lacking in this specimen but will be discussed with individual 2. The frontals are large and rectangular in outline, as exposed on the vertex of the skull, with posterior, oblique extensions between the maxillae and supraoccipital. ‘The exterior edge of the frontal shows a smooth and barely perceptible union with the maxillary. The frontal slopes slightly externally and posteriorly. The supra- occipital reaches forward to the frontals in a high sharp arc which differs considerably from individual 2. MIOCENE MARINE MAMMALS 79 Lateral view—The maxilla and underlying frontal have a common external edge, in the vertical plane, which overhangs the parietal as far forward as the posterior process of the supra- orbital process of the frontal. The zygomatic process is long and directed upward in an anterior direction, and the close approxi- mation of the zygoma to the common edge of the maxilla and frontal shows that contact was almost established in these three bones at the anterior point of the zygoma. As a result of this meeting of these bones, the parietal has been constricted ante- riorly and recurved; and the internal part of the squamosal has been compressed and thickened. The posterior process of the supraorbital has the same shape and position as in T'ursiops. It furnishes the posterior dorsal border of the orbit and defines the anterior border of the temporal fossa. The supraorbital process is quite thin posteriorly but thickens at its anterior edge. Its dorso-external margin is not covered by the maxilla for a width of 11 mm., a character common to Twrsiops. Also, the maxilla is thickened at its point of union with the lacrimal, another feature common to Twrsiops. The lacrimal is fairly large for a dolphin of this size and unites with both maxilla and supraorbital. No suture is shown between lacrimal and jugal. The styliform process of the jugal is preserved for a few milli- meters. It is thin and narrow, as in the modern dolphins. Posterior view—The outstanding character of this view is the almost modern cast of the whole posterior part of the skull. With the exception of the size of the occipital condyles, which in Miodelphis are quite small, the occipital portion of the skull of this Miocene form, notwithstanding its much smaller dimensions, resembles that of the modern T'ursiops. The lambdoidal crest of M. californicus is a smoothly rounded, slightly raised ridge from its anterior limit to the junction of the parietal and supra- occipital, where a slight backward projection occurs, which is very suggestive of the corresponding crest in the modern Tursiops. The foramen magnum is nearly round and of moderate size. The condyles show a distinct neck, laterally, which is dis- 80 PEABODY MUSEUM OF NATURAL HISTORY MEASUREMENTS OF SKULL Total length of specimen, as preserved, from tip of left pre- maxilla, on a level with the maxillary notch, to posterior surface of Jeft occipital condyle. 32....4: << osences- eee 174 Maximum transverse semi-width from median line of frontals to’ external ‘edge of zygomatic process... . 3)... sam os aes 80 Maximum transverse semi-width from mid-line of presphenoid to external edge of posterior process of supraorbital..... 78 Maximum width between posterior external edges of premax- BRE: isin eis in watein a Wi aisles bs mike ai eialae's WOM roe Len ee ee 72 Closest approach of premaxillae near vertex of skull........ 40 Width across premaxillae at level of maxillary notches...... 53 Distance between external edges of maxillae at level of pos- terior process’ of! supraorbital..(<¢ i. :<2.).-<)s; adiel<'a' sao ea 138 Transverse diameter of left maxilla at level of anterior bor- ders’ of choanae:.... ois nace ay ase oii bela ae ee ee 37 Transverse width of left maxilla from external border to point of contact between premaxilla and frontal, measured normalto external iborder...31:)5 caesar 53.5 Length of nasals.along median. suture....3..4.. ss «ne eae 20.6 Asiterior ‘width iof Jett. masalet,<.. 4: 5.ciet sieveucde nueios oat eee 19 Width of supraoccipital near posterior edges of maxillae..... 90.5 Maximum distance between external edges of occipital con- Gyles sh RFS Ot FRC aAE a Biren cena isha ais cae ae ene 63.5 Maximum transverse width of left occipital condyle......... 19.5 Maximum dorso-ventral height of left occipital condyle...... 29 Vertical height of foramen, magnum’... oa. 22 si). 040 oe eee 30 Maximom width of foramen magnum. .... 2.2% 000.000 ee=e 31 Maximum length of right zygoma (as preserved)........... 57.5 Distance from superior internal border of left occipital con- dyle to farthest extremity of left exoccipital........... 64 Maximum length of supraorbital process of left frontal...... 71 Length of posterior process of left supraorbital............ 21 Width of posterior process of left supraorbital at base....... 19.4 Depth of skull from inferior surface of basioccipital to a line from superior side of supracceipital.. 002.2. aes see 91 Depth of rostrum at level of maxillary notches............ 52 continuous dorsally and ventrally. The condyles reach well down on the ventral side. The exoccipitals are thick bones situated close to the condyles instead of far forward as in T'ursiops. MIOCENE MARINE MAMMALS 81 Ventral wiew.—The basioccipital forms a narrow but deep U-shaped trough with steep sides converging somewhat anteriorly. The notch for the jugular leash is deeply inset against the exoc- cipital. The large hypoglossal foramen is found below this notch a distance equal to the depth of the notch. A fracture follows the external, posterior edge of the basioccipital, passes internally around the left occipital condyle and extends a short distance into the supraoccipital. The left side is depressed two or three millimeters along the fracture. The left, triangular falcate process is fairly well preserved and becomes narrow and thick in its ventral extremity. While the above comparisons have been made with T'ursiops, it is realized that the features compared are similar, also, to those in Sotalia, Steno, and Cephalorhynchus. In other words, Miodel- phis californicus represents a generalized type of dolphin from the lower middle Miocene. Hyoid Bones Thyrohyal.—The right thyrohyal is complete except for the superior tip. Its broad, dorso-ventrally flattened end which articulates with the basihyal is rugose; and although there are some indications of exostosis on the ventral margin, the proba- bility is that these elements were separate. The superior surface is strongly concave, with thin, upturned edges. The widest part of the thyrohyal is near the middle where a short, broad pro- tuberance projects anteriorly. Toward the superior end the edges disappear and the bone becomes circular in cross section. A second hyoid bone referred to Miodelphis californicus is incomplete. It lacks both ends and, accordingly, can not be determined accurately. MEASUREMENTS OF THYROHYAL Sreates: lenoth (as, preserved) hi.) 22 sesh ence cc slg eee 88 eee SE WEL HE® vii a0 "5 ahs 4,5. 5 Det oeen aaa RASS Sal eck eee 20 TRO RATE SS SORA AGE 2 orao5 oo csiocd sd 5) he oreea RoR kel als AICS See eee 8.4 82 PEABODY MUSEUM OF NATURAL HISTORY Vertebrae Cervical—The fifth cervical is incomplete, lacking the right post-zygapophysis and both transverse processes on the left side. The neural arch is narrow, gently sloping, and bears a short neural spine. The spatula-like anterior articular facets slope obliquely forward and slightly downward. The pedicles are robust and, at the base, extend nearly the full length of the centrum. The right arterial canal is very large and almost round. The diapophysis is short and bent forward, while the elongated para- pophysis is curved backwards. The centrum is long in com- parison with its height and width and has large depressions, two on the dorsal, two on the ventral, and one on each lateral surface. Dorsal_—The second dorsal vertebra agrees well in size and shape with the fifth cervical, except that it is somewhat longer. The right transverse process, the right anterior articular process, and the tip of the neural spine are lacking. The neural arch is broad, gently sloping, and bears a stout spine. The anterior articular processes are inclined obliquely and have a steep, internal slope. The postzygapophysial facets are slightly con- cave, with raised external edges, and are spatula-like in shape. The left transverse process reaches in front of the anterior edge of the centrum and bears a large, rounded, concave facet for articulation with the tubercle of a rib. On each side of the centrum anteriorly is a half facet for articulation with the head of a rib. A similar facet is located on the hinder border. The neural canal is roughly heart-shaped and wider than high. The transverse diameter of the centrum exceeds the vertical height. ? Miodelphis californicus Fig. 17 Referred specimen.—Cat. No. 13431 Y. P. M. In the pit with the type skull of Miodelphis californicus were found the hinder portions of the right and left mandibles, as well as the third, fourth, and fifth cervical vertebrae, a middle lumbar, the left scapula, the left ulna, the proximal part of the left radius, MIOCENE MARINE MAMMALS 83 MEASUREMENTS OF VERTEBRAE 5th 2d Cervical Dorsal Greatest depth (vertically) of vertebra (tip of neural spine to inferior face of centrum)....... 67 85p Greatest depth of neural canal anteriorly.......... 21.6 19 Greatest breadth of neural canal posteriorly....... 39 35.7 Height, anterior face of centrum................. 33.4 33 Breadth, anterior face of centrum (including facet)... 40- 49.5 Height, posterior face of centrum................ 34,2 31.7 Breadth, posterior face of centrum (including facet) 41 50 Greatest mengthvor Centrum. a2... 6)2 2 ec = «ele siecle 21.5 29 Maximum distance across vertebra between external edges of prezygapophyses.........-.....-.-.- 66 69+ Maximum distance across vertebra between external edges of postzygapophyses...............--- 638.5 58 Distance between tip of left prezygapophysis and left postzygapophysis ........60 cece ese ee ees 33 4d Antero-posterior breadth of spine at neural arch.... 11 19.3 p = as preserved two carpals, one phalanx, and three ribs. The relative dimen- sions of all these elements indicate they belong together. These specimens are tentatively allocated to Miodelphis californicus. Mandible The rami are the same size and shape as those of Steno (U. S. N. M. No. 21169) except that this specimen (Y. P. M. No. 13431) has a larger coronoid process, and its alveoli are smaller and approach nearer the condyle in a posterior direction. These rami also resemble Priscodelphinus atropius (U. S. N. M. No. 10770) in size and shape. The left ramus, from the seventh alveolus to the condyle, is only slightly damaged. Excepting the coronoid and condyle, the bone is thin and fragile. This part of the ramus is straight internally and strongly convex externally. The degree of con- vexity gradually increases in a posterior direction until just before the condyle is reached, where the central part of the ramus is nearly round, with more flattened dorsal and ventral portions. 84 PEABODY MUSEUM OF NATURAL HISTORY The condyle is small and eroded on its superior edge and extends externally beyond the rest of the ramus. The coronoid is a long, gradually sloping, internally concave elevation of heavy bone, beginning about 28 mm. behind the alveolar groove and extending in a posterior direction a distance of 75 mm. to its posterior break. Its posterior part has been damaged. On the internal face of the ramus, near the anterior end of the coronoid, is the large inferior dental canal. The entrance to the dental canal is extremely wide and infundibuliform, occupying practically the entire internal side of the ramus. Its floor is furnished by a short, internally curved portion of the ramus; the roof is sup- Fig. 17. Left ramus of Miodelphis californicus?, external view. x 3/8, plied by a thin layer of bone descending from the coronoid process. The canal is open posteriorly. Extending in an anterior direction from the anterior limit of the inferior dental canal, is a broad, shallow, gently curved groove, which disappears at about the level of the posterior edge of the alveolar groove. The coro- noid process passes anteriorly into the flat, narrow, superior margin of the ramus, which in turn passes quickly into the alve- olar groove. The alveoli are nearly round and are regularly spaced. There are 7 alveoli in a space of 48 mm. In the seventh alveolus, counting forward from the most posterior alveolus, is an incomplete tooth, the antero-posterior diameter of which is 4.4 mm. at the level of the septa. The transverse diam- eter is 4mm. The tooth is broken off unevenly at the base of the crown. The base of the crown is round and has a diameter of MIOCENE MARINE MAMMALS 85 3.5mm. The internal border of the alveolar groove is noticeably higher than the external. The right ramus differs from the left in the absence of the condyle, teeth, and coronoid process. The alveolar groove is eroded so that no count of alveoli can be made. MerasurEMENTsS oF MANDIBLES Motalslengchas Preserved oc... .\sjes calc) s oleicis © oles 205 167 Maximum width at level of anterior edge of inferior Ceuta eran s aie .c'e wiejete siecherorci ere: tess axe lore, ores 14.5 19 Maximum depth at level of top of coronoid to base Gly EAMG MER. sn eie Acts rae idiueietel ale “ae helo tiehs sie 78 x Maximum dorso-ventral diameter of condyle....... 36.7 x Maximum transverse diameter of condyle......... 16 x Length of entrance to dental canal, condyle to closed POTLIOTT e GeoS & Einced bie Care, Cp iCuC rc Oa ice IbsetoioNo Aric 96 x Height of entrance to dental canal at level of top of CGEOH ON yas ca tate, ele tere) ote! ore fe) ole slecal rele araisye. ei aiss 50 x Vertebrae Cervical.—Three cervical vertebrae, the third, fourth, and fifth, are tentatively placed with this specimen. The thickness of the centra of these vertebrae agrees fairly well with corre- sponding vertebrae of Eurhinodelphis sp. (U. S. N. M. No. 10479). These cervicals differ from Eurhinodelphis in their rapid transition from thin to thick centra. Since the fourth and fifth are in contact, there seems to be no doubt about their posi- tion; yet they differ considerably in thickness. The third cervical lacks the neural arch and transverse processes. The fourth lacks the processes. The right pedicle of the neural arch and the right prezygapophysis are present. The anterior articular facet is concave, axially long, and nearly horizontal in position. Its length is approximately twice its width. The arterial canal is fairly small, deep, and well rounded. The fifth cervical lacks the right side and transverse processes. The left pedicle is present with its anterior articular facet and a small piece of the neural arch attached to it. 86 PEABODY MUSEUM OF NATURAL HISTORY MEASUREMENTS OF CERVICALS 3d Ath 5th Maximum length of centrum............. Fei) 22 23 Maximum width of centrum.............. 49.5 52 51= Bleiaht of centrumini) 3s 2 eyeye de s16,@\ =F slevayeriese| sem e)ersiele 70 Minimum antero-posterior breadth of left transverse process.. 35 Distance across external edges of prezygapophyses.......... 28.3 Antero-posterior width of neural spine at level of prezyga- pophysis and including prezygapophysis............... 71 Vertical height of neural spine (from superior limit of neural canal to tip of spine on posterior side) /.. .655 jc. 5). 0 88 Antero-posterior width of spine at superior extremity....... AT Miodelphis californicus (Individual 2) Figs. 18-19 Referred specimen.—Cat. No. 18405 Y. P. M. This specimen consists of an incomplete skull in which the rostrum is broken off at the level of the maxillary notches, the supraoccipital is broken away 35 mm. to the rear of its anterior edge, and all the posterior portion of the skull behind this is lacking. The left maxilla and premaxilla are complete as far forward as the maxillary notch, with the attached supraorbital process, lacrimal, and part of the jugal. The supraorbital process is lacking on the right side, as is part of the maxilla. On the dorsal side, this specimen exhibits the same features as the type except that the nasals, lacking in the type, are prac- tically complete. The supraoccipital of this skull has a wide, shallow arc at the lambdoidal edge and a gradual postero-ventral slope, while that of the type shows a much steeper slope and a wide longitudinal depression. Individual 2 is a larger dolphin than the type and, fortunately, gives additional information. Location.—N. W. 14 of Section 18, T. 26 S., R. 28 E., M. D. 92 PEABODY MUSEUM OF NATURAL HISTORY B. & M., at the top of a hill shown in this locality on Woody Quadrangle, U. S. Geological Survey, near the main road to Woody, Kern County, California. Horizon.—Near the top of the Pyramid Hills Sand described above. Skull This skull is characterized by a very wide maxilla, large frontals, gently-sloping supraoccipital, and long nasals. Dorsal view.—The preserved parts of the premaxillae are quite Fig. 18. Miodelphis californicus (individual 2), dorsal view. x 2/5. For explanation of lettering, see Fig. 1. definitely separated into two distinct portions by a narrow groove that passes through the premaxillary foramen and continues to the posterior extremity of the premaxilla. The premaxillary fora- men is located 14 mm. behind a transverse line from the maxillary notch. At the level of the maxillary notches, the outside part has a width of 11 mm. and the inside part, 10 mm. The outside part of the premaxilla rapidly narrows in a posterior direction to a point on a line with the anterior part of the nares, where it MIOCENE MARINE MAMMALS 93 thins to a width of 2 mm. and then gradually flares out to a width of 12mm. The premaxilla is carried back to the posterior edge of the nasals. At its widest place, the complete premaxilla is 35.5 mm., the broad, superior part representing 30 mm. of this width. The maxillae, like the premaxillae, are thick at the point opposite the maxillary notch. The maxilla fails to overspread the supraorbital process at both ends but along the middle portion almost reaches the external edge. The external ante- rior surface of the supraorbital process is uncovered for a width of 13 mm. (maximum). The posterior surface is uncovered for a width of 20 mm. The maximum width of the maxilla, just above the posterior downward projection of the supraorbital process, is 50 mm. The anterior maxillary foramen is 25.5 mm. behind a transverse line from the maxillary notch, and the ante- rior edge of the foramen is 23.9 mm. from the external edge of the maxilla. A posterior maxillary foramen is located on a line - with the anterior edges of the nasals, and its anterior edge is 25.5 mm. from the external edge of the maxilla, measured along this transverse line. The union of the maxilla with the supraoccipital forms a ridge, sharp at the exterior edge, then rounded, and finally flattened at its junction with the exterior edge of the left frontal. The supraorbital process of the frontal is sharply curved on the infero-posterior side, forming a rounded triangular portion with a base 31 mm. wide where it adjoins the maxilla. This projection is not covered by the overspreading of the maxilla. The curve of the orbit flattens at the top quite sud- denly and then descends in an anterior direction in a gentle curve and slope. The highest part of the orbit is marked by the maxi- mum thinness (2.1 mm.) of the supraorbital process. From this place, it thickens rapidly in both posterior and anterior direc- tions. The frontals are noticeably large and rectangular in shape, except for the extension into serrated peaks at each exte- rior corner. ‘The posterior peaks extend between the supra- occipital and maxillaries. Each anterior extension is bounded by the nasal, the maxilla, and the premaxilla. Otherwise, the 94 PEABODY MUSEUM OF NATURAL HISTORY frontals are rectangular in form. The length of the frontals is noticeably greater than the width. They meet in a well-marked medial suture, which extends unbroken between the nasals. The general appearance of the frontals is flat, with a gentle arching toward the center; and their considerable breadth gives a trans- versely-expanded effect to this part of the skull. The nasals are long and overhang the narial openings. The slope from the anterior edge of the frontals to the supero-anterior edge of the nasals is gradual. The nasals are thick and stout at their junction with the frontals but gradually become thinner in an anterior direction and, at the anterior external edge, are less than 2 mm. in thickness but are Fig. 19. Miodelphis californicus (individual 2), lateral view. x 2/5. For explanation of lettering, see Fig. 1. somewhat heavier on the medial edge. Both nasals are cracked near the base, the right having been somewhat displaced in an anterior direction. The left one is in place. The mesethmoid extends under the projection of the nasals. It is much less robust than in the Acrodelphis species described above. The supra- occipital rounds off gradually from its apex and is smooth and regular in the part that is preserved, except on the exterior edges, where there are small semi-lateral ridges for muscle attachment. A groove begins 23 mm. behind the low lambdoidal crest and MIOCENE MARINE MAMMALS 95 extends in a postero-inferior direction to the broken edge of the supraoccipital. Ventral view.—The lines of division between the lacrimal and the supraorbital process and maxilla are distinct, but no sugges- tion of a suture can be observed between the lacrimal and the anterior basal portion of the jugal. The lacrimal has a wide and heavy superior portion at its union with the supraorbital and maxilla, where it is morticed to both these bones. It con- tracts considerably over most of its middle distance and thins in the direction of the maxillary notch. The basal portion of the jugal is of moderate thickness, covers the entire inferior portion below the maxillary notch, and then is attenuated to form the small stem-like styliform process that extends backward. The palatine vacuities are separated by a distance of 12 mm. instead of meeting in the medial line as in Acrodelphis bakersfieldensis. Just posterior to the palatine vacuities are two grooves extending from the medial line to the optic canal. At the internal limits of these grooves are the internal parts of the pterygoids, the anterior parts of which are made of thin bone. The heavy, pillar- like walls of the basioccipital have a maximum lateral thickness of 15 mm. each. Between these two elevated portions is a U-shaped depression which forms the floor of the basioccipital and has a minimum vertical thickness of 3.7 mm., and a transverse width of 18 mm. An indistinct line within the major depression probably represents a fused suture where the posterior part of the pterygoids and the vomer adjoin the basioccipital. From this suture, the vomer extends in an anterior direction, sheathing the presphenoid. The basioccipital is broken away just behind the union with the pterygoids. The brain case is much narrower in front than behind, and the rostral, or anterior wall, shows either a division and pairing or else a worn break of a medial ridge. The superior portion of the brain case is irregular and indented. The two cerebral hemispheres were separated by a wide rounded depression. The ventral wall of the brain case has many small depressions in addition to the two principal ones. 96 PEABODY MUSEUM OF NATURAL HISTORY Sxutut MrasurREMENTS Total length of specimen, as preserved, from broken left maxilla adjoining maxillary notch in a direct line to broken‘ edge of ;supracccipital 0.5. taste ee Maximum transverse semi-width of skull from posterior ex- tension of supraorbital process to the medial line....... Maximum distance across premaxillae on same line as above MEASUTEMENE 220 ce ccc esse eet seeresrcsavesees Greatest distance between outside margins of premaxillaries at level of anterior border of narial passages........... Greatest breadth of left premaxillary at level of anterior bor- der, of; narial) passawes!) ei. = eel oreo is cite eee Greatest breadth of left premaxillary at level of maxillary TIOUGHA: teco aie) Shei peso uncle e elie © ened coc ene Distance between inner margins of premaxillaries at level of anterior mMargine ‘of masals jc... 22 is ca. sys «ene Maximum transverse diameter of right premaxillary at level of MAKiall. PASSAGES ie.) <1 6 orate oecialacets Ola mi ededaes Wee el ciele eeeee Greatest vertical depth of skull at level of anterior borders of MATIAL PASSAVES) (. Sac. o ices wis, des Se “ieee k= fags See eee Greatest vertical depth of rostrum at level of maxillary notches Least distance between inner margins of maxillaries on vertex OF SOU. 25k Vn ce eee eens cle Oe oe ake oie Maximum transverse diameter of combined nasals.......... Maximum transverse diameter of left nasal............... Maximum antero-posterior diameter of left nasal........... Distance from level of anterior edges of nasals to anterior edge of supraoccipital medially’. . oi \yc): ia << osc eine eee Maximum antero-posterior diameter of frontals along median suburals NG: j6.ccaicis io 2 o.a oso ein aie bie 0, se arse ate eee ee Least transverse width of left: frontal... ...:. 0... .-msevne Least transverse width of right frontal..........0.. 01220. Maximum oblique diameter of left frontal.................. Greatest antero-posterior diameter of left supraorbital process of Promtalis soja o «ia ty asc: sure gists ore ae beepers akeete ele ee Greatest antero-posterior length of superior part of lacrimal.. 167 100 78.4 78 35.5 21 33 32 83 51 43 38 19.4 18.1 45 26 20.6 22 43.1 78 20.6 MIOCENE MARINE MAMMALS 97 Family INIIDAE DOLIODELPHIS,” new genus Genotype.—Doliodelphis littlei,** new species. Diagnosis —Resembling porpoises belonging to the family Iniidae in the great thickness of frontal on the vertex of the skull, the deeply indented maxillary notches at the base of the rostrum, and the strong tapering of the slender preorbital apophysis of the maxilla. Doliodelphis littlei, new species Figs. 20-21 Holotype.—Cat. No. 13404 Y. P. M. The skull is in two pieces, having been split longitudinally approximately through the center, thus exposing the choanae and surrounding bones in an excellent manner. The skull is incom- plete, lacking the distal part of the rostrum, the right frontal, right nasal, the premaxillae and dorsal surface of the maxillae in front of the maxillary notches, left supraorbital process of frontal, postero-external portions of maxillae, and occipital portion of the skull. It differs from recent Iniidae in the denti- tion and also in several other respects. Type locality —N. W. 14 of Section 13, T. 26 S., R. 28 E., M. D. B. & M., on the west slope of a round hill and just east of the main road to Woody, Kern County, California. This skull was found by Mr. T. V. Little and the writer in the spring of 1930. Horizon.—Pyramid Hills Sand, about 100 feet below ? Macro- delphinus kelloggi, No. 18412. Skull The general configuration of this cetacean skull leads one to believe that if the lateral compression by the maxillaries against 37. dédu0s, deceptive; deddis, porpoise. 38. Named in honor of one of its discoverers, Mr. Thurston V. Little, of Shafter, California. 98 PEABODY MUSEUM OF NATURAL HISTORY the vertex of the skull and the forward thrusting against the pre- maxillae were to continue along the lines of development indicated by this specimen, a condition like that in the modern Lipotes (U. S. N. M. No. 218293) or Inia (U. S. N. M. No. 49582) would probably result. But the structural condition in Doliodel- phis littlet shows that these modern forms have undergone consid- erable remodeling, particularly in the maxillae, which have been modified from a horizontal plate to an elevated and concavely curved surface, in the premaxillae, which have moved anteriorly from the apex, and in the frontals, which have been greatly ele- vated. While the skull of Doliodelphis littlet appears to have started in this direction, it can not be classed with modern Iniidae on account of the differences just mentioned and also the differ- ences in dentition. No teeth of this specimen are preserved, but the left maxilla has 22 alveoli in a distance of 157 mm., counting from the hindermost alveolus forward. Inia geoffrensis Blainville* shows 22 teeth in 199.5 mm., much too large a ratio for Doliodel- phis littlet. Stenodelphis blainvillei P. Gervais*® shows 22 teeth in a distance of 88 mm., much too small a ratio. The structural peculiarities of these two recent porpoises (Winge*') indicate that the fossil specimen herein described probably lies between these two extremes and may possibly be ancestral to one or to both. Hesperocetus californicus*’ is much too large to possess any near affinity to this form. Nor can Eoplatanista ttalica Dal Piaz** be closely related, since, in the middle portion of the left rostrum, it possesses 8 teeth in a distance of 83 mm., or 1 in 10.4 mm., while Doliodelphis littlet has 1 in 7 mm. Nor are any 39. Abel, O.—Op. cit., vol. I, fig. 5, 1901. 40. Ibid., fig. 4. 41, Winge, H., and Miller, G. S—A review of the interrelationships of the Cetacea. Smithson. Mise. Coll., vol. 72, no. 8, pp. 228-235, 1921. 42, True, F. W.—A fossil toothed cetacean from California, representing a new genus and species. Smithson. Misc. Coll., vol. 60, no. 11, pp. 1-7, 2 pls. 1912, 43, Dal Piaz, G.—Gli Odontoceti del Miocene Bellunese. Parte Quarta, Eoplatanista italica. Mem. dell’Istituto Geologico della R. Universita di Pedova, vol. 5, tav. IT, 1916. MIOCENE MARINE MAMMALS 99 of the species of Abel’s** Platanistidae sufficiently like the one under discussion to necessitate any detailed comment. Dorsal view.—The premaxillae are largely destroyed anterior to the premaxillary foramina; and hence the distinguishing fea- tures of their dorsal surfaces are lacking. The premaxillary foramen is deep, and a groove runs from it posteriorly, dividing the premaxilla into two distinct parts, a broad, slightly concave portion which rises above the groove on the internal side, rising rather sharply as it approaches the nasal, and a narrow portion which slopes away from the groove laterally and posteriorly and flares widely at its posterior limit. At its posterior extremity, the lower portion of the premaxilla rests on the maxillary, and the upper portion is bifurcated, one point meeting the extreme anterior edge of the frontal, and the other point being wedged in between the extreme anterior projection of the frontal and the lateral face of the nasal. Although part of the inner portion of the right premaxillary is eroded, it is apparent that the two premaxillae did not approach each other closely posterior to the premaxillary foramina. The mesorostral gutter is, accordingly, completely open at the top and exposed from the anterior tip of the specimen to the presphenoid. The left maxillary is mostly lacking posterior to the maxillary notch. The dorsal surface of the right maxillary is almost all eroded, and part of the posterior portion of this bone is broken away. The maxillary is broad and high behind the maxillary notch and overlaps the supraorbital process of the frontal. This overlapping of the supraorbital process is nearly complete at its apex, covering all but 3.3 mm. But near the anterior edge, there is an exposed surface of 13 mm.; and at the extreme anterior edge, the maxilla extends in a blunt point slightly beyond the lacrimal. The maxillary notch is broadly curved, the anterior edge ascending gradually to the point where the maxillary overrides the lacrimal. The maxillary foramen is deeply incised, with a broad, deep groove extending a 44, Abel, O.—Untersuchungen iiber die fossilen Platanistiden des Wiener Beckens. Denks. Akad. Wiss., Wien, Math.-naturw. Classe, Bd. LX VIII, 1900. EZ ——a /D.14S010SAU) “ty Ute S_ — SS uvado sayne —— WW ee $.0C. Max. Fig. 20. Doliodelphis littlei (holotype), dorsal view. x 7/2. For explanation of lettering, see Fig. 1. MIOCENE MARINE MAMMALS 101 short distance from it both anteriorly and posteriorly. The right nasal is lacking, and the left one is incomplete, with the inner half destroyed. A projection from the ventral anterior part of the nasal forms a shelf on which an extension of the mesethmoid may have rested. The right frontal is broken off. The exposed sur- face of the left frontal is rather irregular in outline and emar- ginate. The posterior portion is prolonged into a point that extends laterally along the anterior edge of the supraoccipital crest. A V-shaped suture is formed at the anterior border of the frontal. The lateral arm of the V is long and sharp-pointed and is bordered by the maxilla on one side and the premaxilla Fig. 21. Doliodelphis littlei (holotype), lateral view. x 1/4. and nasal on the other side. The medial line of the V is less sharp, and its end is posterior to the end of the lateral arm. If the right frontal were present, the line forming the anterior border of the combined frontals would form the letter W. The narial openings slant forward and downward at a slight angle in the dorsal view and curve posteriorly as they approach the ventral side of the skull. The posterior portion of the skull is lacking. A high, narrow but rounded lambdoidal crest on the supraoccipital is visible along the posterior border of the left frontal. The supraoccipital seemingly descends abruptly from this crest. The frontals are thick, at least 23.2 mm., at the level of the occipital crest. This thickness rapidly diminishes in a 102 PEABODY MUSEUM OF NATURAL HISTORY posterior direction, because of the steep descent of the supra- occipital. Ventral view.—The outstanding features of this view are the height of the presphenoid between the pterygoids, the preser- vation of the posterior part of the mandible collapsed against the skull, and the height and position of the pterygoids. The left maxilla shows 22 alveoli in a distance of 157 mm. counting forward from the most posterior alveolus. The maxil- laries are rounded at the anterior end of the specimen, being much more steep on the interior edge where it descends abruptly to meet the vomer. In a posterior direction, the maxillary becomes more broad and flat, descending very gradually on the external edge to the alveolar groove. The posterior part of the alveolar groove is eroded so that the alveoli can not be counted. The vomer is visible from the anterior end of the specimen for a dis- tance of 105 mm., where it passes under the internal edges of the maxillaries. It is next seen as a high crest between the ptery- goids and is then broken away just at the posterior edges of the narial openings. The palatine vacuities are covered by the pieces of the mandible which have been collapsed on the ventral side of the skull. The left infraorbital foramen appears as a wide groove passing from the exterior edge of the broken maxilla to the under surface of the premaxilla. The optic canal is of moderate width and depth on its interior side and opens to a broad, shallow depression as it passes to the under side of the frontal plate. The pterygoids are well preserved laterally and anteriorly but broken posteriorly. The anterior edges are thin and the posterior parts, thick. The crest of the vomer extends above the tops of the pterygoids a distance of 16 mm. The lacrimal is separated clearly from the supraorbital process of the frontal and from the maxillary at the exterior edge but shows no suture on the interior edge. Evidence of separation of the lacrimal from the base of the jugal can not be seen. Only the base of the jugal is preserved, and it is thin and narrow. The brain case is rugose and shows the olfactory foramina, which are small but set in MIOCENE MARINE MAMMALS 108 fairly large depressions. The anterior part of the brain case is considerably narrower than the posterior part. MEASUREMENTS OF SKULL Total length of specimen as preserved, measured from anterior edge of left maxilla to posterior edge of the supraoccipital, HGSDPCSOEV ECs: tayo. cng speeds sa) aaa 2 5/2. pick) sa) 0, ais aie « Maximum semi-width from median line to exterior edge of supraorbital process of right frontal at level of the pre- MEE aT FOLATO CH coer. Counc: Scfel tei s a lane sucgoreim © el ots (onde. wey Maximum distance across premaxillaries at level of anterior edges of posterior premaxillary foramina.............. Greatest distance between outside margins of premaxillaries at level of anterior edges of narial passages........... Maximum width of left premaxillary at level of anterior edges Oi Gorsal MATIAlLOPENENPS cba s. — = 2 € Ps od . ; 5 « - = = === =e Ss —, “wha> QS CE Fig. 22. Eurhinodelphis extensus (holotype), dorsal view. x 1/3. For explanation of lettering, see Fig. 1. foramen to the end of the preserved portion of the rostrum. Also, a groove extends posteriorly from the premaxillary foramen, disappearing toward the posterior extremity of the premaxilla. Behind the premaxillary foramen, the premaxilla rises gradually to the anterior edge of the narial opening and then rises steeply to form part of the vertex of the skull at the posterior extremity of the premaxillary. The premaxilla extends posteriorly far behind the nasals. 108 PEABODY MUSEUM OF NATURAL HISTORY The vertex of the skull is flat except for the portion formed by the nasals. The nasals rise slightly above the narial openings but do not overreach them (as in Acrodelphis bakersfieldensis). The narial openings are long and narrow, and somewhat elliptical in outline at the dorsal side, and approximately the same size. Each opening really consists of two parts, the narial passage itself, which is round and anterior in position, and the posterior part, which is an irregularly shaped depression lying behind the rounded anterior opening and having a floor lying a distance of 49 mm. below the top of the medial line of the nasals. Near the Km, Fig. 23. Eurhinodelphis extensus (holotype), lateral view. x 1/3. For explanation of lettering, see Fig. 1. bottom of the posterior part, two vascular foramina appear as small holes. The distance from the posterior edge of the rounded anterior part to the rear of the irregular platform, measured in an antero-posterior direction, is 14.5 mm. This platform, or floor, is formed by the mesethmoid. Only the upper portion of the supraoccipital is present. At its contact with the frontals, it forms a ridge which overhangs the supraoccipital posteriorly. Beneath this overhanging ridge, the supraoccipital descends nearly vertically for approximately 7 mm. and then slopes more gradually. The central portion of the supraoccipital is depressed and bordered laterally by ridges which extend to join the over- hanging ridge at the vertex. Several rugosities running dorso- ventrally occur in this depression, and one of them forms a ridge MIOCENE MARINE MAMMALS 109 running from the overhanging crest medially for a distance of 17 mm. The frontals show a combined anterior breadth of 31.5 mm. and a posterior breadth of 80 mm. at the maximum. The antero-posterior length of the frontals along the medial line is 22mm. The longitudinal suture is not clearly defined ; and hence, the frontals can not be described separately. The nasals extend forward only to the posterior edges of the narial openings. Each nasal is roughly rectangular in shape. The maximum antero- posterior length of the left nasal through its approximate center is 15 mm., with the right nasal the same size. It is interesting to find that there is no apparent asymmetry in this part of the specimen. Ventral view.—The two rounded narial openings appear clearly in this view, widely separated by the deep, robust presphenoid. The transverse diameter of each narial opening is 18.5 mm. The palatine vacuities show a maximum length of 32 mm. (left) and 37 mm. (right). At the medial line, the vacuities are separated by a minimum width of 13 mm. The indentation of these vacuities and the associated posterior depressions is deep. The optic canals, with the walls partially preserved, are deep and somewhat rugose dorsally and lie quite close to the narial openings (3.5 mm.). The maxillae are gently rounded in this view except at the inner, anterior edges, where an abrupt, steep slope is observed. The infraorbital foramen is quite large and preserved only on the right side. Its anterior edge lies 22 mm. behind a transverse line drawn from the maxillary notch. This foramen flares out widely at its posterior end. Only the base of the anterior part of the jugal is present. It is broadened in an oblique, antero-posterior direction, thinned at right angles to this direction, and stronger than the corresponding part of the jugal in Acrodelphis bakers- fieldensis. Not enovgh of the dental groove is preserved to obtain information on the teeth. This groove ends just 18 mm. in front of the maxillary notch. The dorsal part of the brain case is well preserved, and parts of the bounding sides are present. Vascular 110 PEABODY MUSEUM OF NATURAL HISTORY foramina lie at the edge of the presphenoid and anterior frontal plate.