70 



Henry's Forkof Green River, which appears to pertain to a species oi'Lophiothe- 

 rium. The specimen, represented in Fig. 33, Plate VI, consists of a lower- 

 jaw fragment containing the last premolar and the first and last true molars 

 — the crown of the intervening true molar having been lost. The teeth 

 appear closely to resemble in form and constitution those of LophiotherUan 

 cei-vulum, as represented in Plate II of Gervais's Zoologie et PaUontologie 

 franQaises. The only apparent difference, which, nevertheless, is an important 

 generic one, if it really exists, is the division of the summit of the antero- 

 internal lobe of the crown of the teeth into two points in the American fossil. 



The anterior teeth, Fig. 34, of the latter have oblong quadrate crowns, 

 slightly narrower at the fore part and otherwise alike in form. They are 

 quadrilobate, tlie lol^es being tri-laterally pyramidal and connate at base. 



The last molar. Fig. 35, is prolonged behind in the manner so common in allied 

 animals of the same order. This prolongation is mainly due to the addition of 

 a fifth lobe to the crown, which is narrowed posteriorly in the reverse direc- 

 tion to the teeth in advance. 



A strong basal ridge incloses the crowns of the teeth, excepting internally. 

 In the last molar it is less well developed and does not exist posteriorly. The 

 constituent lobes of the crowns are nearly of uniform size. The antero-in- 

 ternal lobe, as before intimated, has its summit divided into two points. The 

 division extends so short a distance that it w<nild be early obliterated from 

 the wearing of the teeth in the trituration of the food. It is hardly percepti- 

 ble, even in the unworn condition in the last molar, and in the specimen is 

 most distinct in the first true molar. As a character, it may l)e inferred to be 

 most obvious in the anterior two true molars, and less so in the premolars of 

 like_form and in the last true molar. 



The postero-internal lobe of the crowns has a simple pointed summit. The 

 inner lobes have the crescentoid summit declining from a central point in- 

 wardly, so common in the corresponding teeth of allied animals. The fore 

 arm of the summit of the antero-ext'ernal lobe is a thick ridge curving to the 

 base of the antero-internal lobe in front. The back arm is a short ridge 

 directed inwardly to the anterior division of the summit of the antero-internal 

 lobe. The fore arm of the summit of the postero-exteinal lobe reaches the 

 middle of the antero-internal lobe. The back arm joins the posterior basal 

 ridge, proiUicing an elevated point at its middle. From the inner side of the 



