624 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



spreading distally, the transverse measurement across 

 the inner and outer toes resting on the ground being 

 240 millimeters. Palaeosyops thus presents a very 

 wide contrast to the relatively narrow fore foot of 

 MesatirMnus. The contemporary species of rhinoc- 

 eros {Amynodon) is also distinguished by the height 



Figure 538. — Pelvis of LimnoMjops (doubtfully referred) 



Am. Mus. 2348, superior view. Washalde ?A. One-sixth natural size. 



and lateral compression of all the elements of the 

 carpus and metacarpus and by the greatly reduced 

 terminal phalanges. 



The pelvis and sacrum in this mounted specimen 

 (Am. Mus. 2348) are from the Washakie Basm, Wyo. 

 As noted above it may belong to Liimiohyops, because 

 the supra-iliac border does not exhibit the uniformly 

 convex arch seen in Palaeosyops. The sacrum, how- 

 ever, differs from that of the type of Limnohyops in 

 being composed of four vertebrae, the last two of 

 which are clearly caudosacrals. The sacral plates ex- 

 tend deeply down the inner sides of the ilia, the total 

 oblique measurement from the summit of the sacral 

 spines to the bottom of these plates being not less than 

 170 millimeters. The greatest width of the plate an- 

 teriorly is 136 millimeters as compared with the total 

 length of the four sacrals, 159 millimeters; the spines 

 are moderately broad, thin, and coalesced at the sum- 

 mits. The fourth or posterior sacral extends the plate 

 well beyond the posterior superior crest of the ilium. 



In general the pelvis (Am. Mus. 2348) is decidedly 

 elongate as compared with that of the Oligocene titano- 

 theres. The total length (465 mm.) is only 23 milli- 

 meters less than the total breadth (488 mm.). The 

 superior crest of the ilium, actually measuring 265 

 millimeters transversely, has a uniformly concave 

 transverse surface with a moderately thickened su- 

 perior border slightly sigmoid — that is, convex in its 

 outer half and straight or slightly concave in its inner 

 half — as it rises to its convex junction with the sa- 

 crum. The distinctive feature of this pelvis is the 



slightly concave "crista iliaca" between the broadly 

 rugose tuber coxae and tuber sacrale. The conforma- 

 tion of this border is analogous to that of Rhinoceros 

 sondaicus and of other quadrupeds the ilia of which 

 are transitional between the purely cursorial type of 

 dium seen in Equus and the weight-carrying type with 

 a uniformly convex superior border seen in Uinta- 

 therium, ElepJias, and Menodus. The neck of the 

 ilium measures 67 millimeters transversely. The me- 

 dian border of the posterior pelvic opening is marked 

 by an elongate sharp ridge constituting the spine of 

 the ischium (origin of gemellus superior, coccygeus, 

 and levator ani muscles) opposite the acetabulum, 

 behind which is the well-defined lesser ischiadic notch. 

 Behind this the ischiadic border is rounded until it 

 passes into the prominent ischiadic tuberosity. The 

 vertical depth of the ischium at this point is 117 milli- 

 meters. The pubo-ischiadic symphysis measures 174 

 millimeters anteroposteriorly. The obturator fora- 

 mina are elongate, oval, measuring 87 millimeters 

 (anteroposterior) by 49 millimeters (transverse), sepa- 

 rated by 19 millimeters, the narrowest point of the 

 symphysis. 



The hind limb has a total length from the head of 

 the femur to the tip of the median phalanx of D. Ill 

 of 940 millimeters as compared with 810, the total 

 length of the fore limb, and 500, the expansion of the 

 ilia. These figures give an idea of the chief propor- 

 tions of the animal. 



The femur (Am. Mus. 1582) measures 370 milli- 

 meters as compared with 290 of the tibia, this exces- 

 sive length of the upper limb being correlated with 



Figure 539. — Pelvis of Palaeosyops of. P. leia 

 Princeton Mus. 10232, superior view. After Earle. One-sixth natural size. 



relatively slow movements. The chief characters of 

 the femur are as follows: The long, straight shaft 

 flattened superiorly on the posterior surface; great 

 trochanter moderately elevated; breadth across head 

 and great trochanter 132 millimeters (estimated) 

 apex of third trochanter 143 millimeters below head 

 apex of second trochanter 132 millimeters below head 



