320 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



may be regarded as a neotype. Agreeing well with 

 this neotype lower jaw is the finely preserved upper 

 dentition Am. Mus. 13032, also from Bridger B 1. 

 Three other jaws (Am. Mus. 11692, 11711, from 

 Grizzly Buttes, Bridger B 2, and 13118, from Moun- 

 tain View, Bridger B 2, Grizzly Buttes) may also be 

 referred to this very primitive species. 



The inferior molar, m^, of Leidy's original type, 

 now taken as the lectotype, measuring (ap. by tr.) 

 33 by 20.5 millimeters, exhibits crescents with striated 

 sides, very low antero-internal cusp, very rudimentary 

 metastylid, prominent entoconid, with a distinctly de- 

 veloped entostylid, also anterior and posterior cingula 

 wanting, even between the valleys. 



The superior premolar type (Nat. Mus. 762, in part) 

 consists of the ectoloph of p^ of the left side and of 

 the inner half of the crown of p* of the right side, 

 two teeth conjoined by wax. The accurate transverse 

 measurement of the crown, therefore, can not be given; 

 the ectoloph measures 19 millimeters anteroposteri- 

 orly and 13 millimeters (estimated) from the base of 

 the crown to the tip of the partially worn protocone; 

 it consists of a prominent anterior style, a protocone, 

 sharply convex externally, spreading into an external 

 cingulum which surrounds the less convex tritocone, a 

 cone which is slightly smaller than its fellow the pro- 

 tocone. The inner half of the crown of p^ of the oppo- 

 site side consists of a deuterocone, a faint ridge ex- 

 tending anteriorly toward the protocone, measuring 

 16 millimeters anteroposteriorly; on either side are 

 anterior and posterior cingula which rise gently to- 

 ward the apex but do not tend to surround the smooth 

 inner side of the protocone; this condition is exactly 

 intermediate between that observed in L. laevidens 

 and P. major. 



As remarked above, the association of these upper 

 teeth with the lower is doubtful; the upper teeth may 

 belong to LimnoTiyops. The second superior molar 

 (Nat. Mus. 758) consists only of the anterior half of 

 the tooth, estimated at 35 millimeters transversely; 

 it exhibits a stout parastyle, a median rib opposite 

 the paracone, a distinct and somewhat transversely 

 elongated protoconule, a low, conical protocone, a low 

 and slightly worn cingulum which rises at the antero- 

 internal edge of the protocone. The anterior cingu- 

 lum is incomplete at a point anterior to the tip of the 

 paracone (cf. P. major, Am. Mus. 12182). The slopes 

 of the cusps, like those of the molars of P. major, are 

 vertically striated. The anterior crescent is consid- 

 erably smaller, whereas in higher stages the two are 

 subequal. 



Specific characters oj the types. — It is difficult to 

 define this species clearly from the lectotype specimens 

 which are described in detail above. Reference should 

 be made to the very carefully prepared natural-size 

 drawings of these teeth on Plates LII and LIX. The 

 following is a provisional definition: 



Second inferior molar (lectotype) with distinct but 

 depressed entoconid, and metastylid and entostylid 

 folds; median ridges within the crescents; cingula not 

 prominent; dimensions, anteroposterior, 33 millimeters; 

 transverse, 20.5; superior premolars without trace of 

 internal cingulum at base of deuterocone; subequal 

 protocone and tritocone on p*, no mesostyle; superior 

 molars with moderately developed cingula and proto- 

 conule, moderately open external crescents. 



The superior teeth referred by Leidy to this species 

 are the principal ones among those described by Leidy 

 as P. paludosus which possibly belong to this primitive 

 species. The figure copied herewith is taken from 

 Leidy's memoir of 1873 (pi. 4, fig. 3). The specimen 

 is recorded from Grizzly Buttes, Bridger Basin, Wyo., 

 probably Bridger B 2. It is seen at once to belong to a 

 small animal in a very simple stage of evolution. The 

 premolar teeth are readily distinguished specifically, 

 as shown in the figure, by the extremely simple charac- 

 ter of the ectoloph of p^; it exhibits not even a rudiment 

 of the tritocone, a cusp which is strongly developed in 

 the geologically successive P. major. The measure- 

 ments of the teeth as figured on Leidy's plate, said to 

 be of natural size, are suspiciously small — namely, 

 p'-m' 137 millimeters, p^-m^ 133 — and may indicate, 

 if the drawing is correct, that the specimen belongs to a 

 smaller form, such as P. longirostris. 



Oshorn's neotype and other referred material. — The 

 neotype jaw (Am. Mus. 11680, fig. 268, B) is referred 

 to the same species as the lectotype (see above) on 

 account of the absolute similarity in form and size of 

 the second inferior molar (m2) in the two specimens. 

 Although small it belongs to a male animal, as indi- 

 cated by the very deep and prominent chin and robust 

 canines, which measure (ap. by tr.) 24 by 22 milli- 

 meters at the base of the crown. The lower borders 

 of the rami are especially thickened beneath the pre- 

 molar series, the vertical depth of ramus in front of p2 

 being 60 millimeters and behind ms 81 or 84. While 

 broad, the anterior face of the lower portion of the 

 coronoid process lacks the concavity which distin- 

 guishes P. major. The grinding series, P2-ni3, 

 measures 152 millimeters as compared with 163 to 169 

 in P. major and 174 in P. rohustus. P2 is in a simple 

 stage, not showing the distinct rudiments either of the 

 paraconid or of the crescentic conformation of the 

 hypoconid. In ps faint rudiments of the paraconid, of 

 the metastylid, fold, and well-developed hypoconid 

 crescents are seen. In p4 all these characters are 

 strongly accented, but this tooth can not be described 

 as molariform, as it still lacks the entoconid, the eleva- 

 tion of the hypoconid, and the equalization of the two 

 lobes. The outline form of this jaw is represented in 

 Figures 267, 268, B, and the detailed characters of the 

 teeth are shown in Plates LVI, LXII, Figure 268. 



Another jaw (Am. Mus. 11711) from the bluff above 

 Mountain View, Bridger Basin, Wyo., Bridger forma- 



