1896.] Geology and Paleontology. 483 



Having now attempted to show that the monodactyle type of foot 

 found in the Upper Eocene of France is in all probability correctly 

 associated with the teeth of Paloplotherium, I shall review the charac- 

 ters of this phylum and indicate those points which parallel the true 

 horses, and also point out those aberrant structures of the teeth which 

 exclude the possibility of placing this series in the direct line leading to 



Through the kindness of Professor Albert Gaudry, I have been en- 

 abled to study a beautifully preserved skull of PaUrplotherixun javvulii 

 from the Phosphorites. This cranium is remarkably like that of the 

 horse in many of its characters, and I think most Paleontologists would 

 say at once that this type of horse-like skull should be associated with 

 a foot tending to raonodactylism. The position of the orbit is as in the 

 primitive horses, its anterior termination being placed over the second 

 true molar. The form of the facial region closely resembles that of the 

 horse, being high and strongly compressed. The premaxillaries are 

 elongated and slender, and slope gradually backwards as in the horse. 

 Among the Palseotheroids, P. crassum has a skull resembling some- 

 what that of PaloplotJu rittm javalii, but in the former the facial region 

 is shorter and broader than in P. javalii. In the skull of P. javalii, 

 there is a large flat area between the orbits, and the sagital crest is well 

 marked. The post-orbital processes of the frontals are largely devel- 

 oped and extends well downwards towards the zygomatic arch. The 

 post-tympanic and paroccipital processes are united as in P 

 crassum. The basal region of the skull in P. javalii is long and narrow, 

 like that of the horse. 



The structure of the skull in Paloplotherium minus is not known, 

 only fragments of the occiput having been found. The teeth of P. 

 javalii have been described by M. Filhol, and as is well known the 

 crowns of the upper molars are much elongated and tending strongly 

 to the hypsodont condition of Equus. Moreover, the valleys between 

 the crests are filled with cements and the external and internal surfaces 

 of the crown are coated with the same substance. 



In Paloploth r'nnn the la.-t upper premolar is completely molariform 

 and the posterior crest of this tooth, and that of the true molars is very 

 oblique in position. The metaloph owing to its oblique position, only 

 unites with the ectoloph after a long period of wear; this crest, in the 

 true horses, moreover, is nearly at right angles to the ectoloph and 

 unites early with the latter. In Paloplotherium also, the hypostyle — 

 an element so essential in the evolution of the horse's molar, is absent. 

 The lower true molars in the Paloploth eroids lack the reduplication of 



