TIIK MAM>rAT.TA OF THE UINTA FOiniATIdX. 513 



single individual ; the Ttlanothen'ain measureraents aio aiiproximatc from specimuns 

 which we have referred to T. yrontll. 



It is remai-kable that the comparatively small genus Palwosf/ops anticipates in 

 so many features the gigantic Miocene genus. The foot structure in almost every 

 detail is persistent, this being the only line of Perissodactyla known in which there 

 is no reduction of the fifth digit. Then we find in Falwosi/ops, as shown in tiie dia- 

 grams, every tarsal articular facet reproduced in the later genus. The neck, in some 

 species at least,* undergoes considerable change in i)roportion, but the doisal >iiiues 

 of the Eocene genus are decidedly elongate and anticipate the great liuinp of Tltaa- 

 otherium. The skull undergoes an entire remodeling, consisting principally in the 

 elevation of the occiput, this being correlated with the elongation of the dorsal ver- 

 tebral spines and development of a powerful ligametdum nuchce to support the nasal 

 horns. The earlici- species of Titanotherium, T. (Megaceratops) coloradense, for exam- 

 ple, retain the long nasals overhanging the premaxillaries which are so characteristic 

 o? I^aheosijops. A feature common to the three genera is the prominence of the lesser 

 trochanter. 



In adtlition to the features ali'cady mentioned as distinguishing the Miocene 

 and Uinta genera from their Eocene ally, we notice the prominent and reeuived del- 

 toid hook of the humerus; the cversion of the major axes of the iiniominate bones, 

 with the marked expansion of the suprailiac border. In the manus and pes, while 

 the facets remain the same, the proportions of the different elements are much altered, 

 as pointed out in a later section. In the pelvis and tarsus, however, as already stated, 

 J)/])hicodon stands nearer the oldL'r than the more recent form. 



In the Washakie beds is found a large sjiecies, about the same size as /^ valli- 

 (huis Cope, which is i)i-ovisionally referred to PaJceosijojis {P. Jnjixjnatlnis, spec, nov., 

 Princeton collection, No. 10,27.'3). This is represented by a lower jaw seven-eighths 

 as large as the type mandil)le of i>/"/>/«cofZo/i. As in the latter, llu' incisors forma 

 close procumbent series; the tips forming a gently aiched line when seen from above. 

 The sym[)hysis is extremely long (11 cm.) and shallow ; the canines are rather small 

 and semi-procumbent. The molar-premolar series measures 24.") cm., the last molar 

 measures 6.5 cm., the transverse measurement outside of the canines is 9.(3 em. ; in 

 Diplacodon ehitns the same measurement is K) em. Unfortunately the premolar 

 crowns are broken; it is probable that one or two of the premolars will be fotmd to 

 be like the molars. The characters of the ehiu and symphysis are significant ofdose 

 relalionshii) to Jjiplacodon elalas. 



• In Prnl. Miirsli's collcrlion IlifTi' on- some cen'kal vcrlcUrii; rcrerruU lo Dii'lucoilon wlii' i' l''v. .il i ili. .^nn.' 



)>ri>|ionicin!il Irnglti iis in Pitlito»yi>ii. 



