LOPHIODON 329 



cingulum. The low posterior lobe (c) shows the rudiment of 

 a second internal cone (d). 



The first molar (fig. 96, m i ) has a pair of front lobes and 

 a pair of hind lobes, with an oblique ridge continued from 

 postero-internal lobe to the interspace between the front pair. 



The second molar (m 2) shows an increase of size ; but 



its chief and most interesting modification is 



the development of a tubercle (e) between the 



two anterior lobes, making three cones on the 



same transverse line, and thus repeating the 



character of the molar tooth of Stcrcognathus 



(fig. 97, c). The oblique ridge from the outer Fig- f J<- 



and hinder lobe (c) abuts against the inter- Tr . ue ? olar - J ™ 

 v ' jaw (magn.j, ^Re- 



mediate tubercle (e). The nearest approach reognathus ooli- 



to the above dentition is made by the extinct tlcus - 



Hyracotherium; also a fossil from the London clay. 



The third trochanter on the femur of Pliolophus, and the 

 association of three metatarsals in one portion of the matrix, 

 as if belonging to the same hind foot, confirm the essentially 

 perissodactyle affinities of that genus as shown by the skull 

 and teeth. Pliolophus and Hyracotherium form a well-marked 

 section in the lophiodont family, which seems to have pre- 

 ceded the palffiotherian family in the order of appearance, and 

 to have retained more of the general ungulate type than that 

 family. This is shown by the graduation of the tapiroid 

 modification of the molar teeth into one more nearly resem- 

 bling that of the Authracotheria and Chmropotami, by the 

 absence of the postero-internal cone on the ultimate premolar, 

 by which all the premolars are, as in artiodactyles, less com- 

 plex than the true molars, by the form and position of the 

 nasal bones and by the structure of the external nostril. 



Genus Lophiodon, Cuv. — In the year 1800 Cuvier* first 

 announced the discovery of the fossi] remains of a quadruped 



* Bulletin rles Sciences, Paris, Nivose, an. viii., No. 34. 



