F. B. Loomis — Hyoj?sodidcB. 423 



cone, there is a strong parastyle. The protoconule is closely 

 united to the protocone. The last molar is large, but still 

 lacks the lrypocone. The 

 third and fourth premolars 

 have the parastjle but lack 

 the intermediates and hypo- 

 cone. 



The species includes the 

 medium sized individuals of 

 the "Wind River, the three 

 lower molars measuring 15 mm . 

 It compares in size to II. 

 lemoinianus but lacks the 



i -i n -i Jig. 7. Hiiopsodus broivni. x f . 



external cingulum, and has a a 



simple metaconid as well as having much more obtuse cusps. 

 There are 45 specimens in the Amherst collection all from 

 Bridger Cr., Wyoming. 



Hyopsoclus jacksoni sp. no v. 



In many ways this is the most specialized of the Hyopsodidce, 

 and it has been named in recognition of the interest and coop- 

 eration of Mr. E. E. Jackson in the Amherst expeditions. The 

 type is a right ramus 

 with the molars and 

 the fourth premolar, 

 and a third premolar 

 from the left side. 

 The co-type contains 

 three upper molars. 



The lower molars 

 are rather narrow 

 with moderately high 

 cusps and a cingulum F 



along the front side 

 only. The metaconid is bifid, strongly so on the first molar, 

 and just visibly so on the last. The protoconid and metaconid 

 are widely separated and connected by the protolophid only. 

 The hypoconulid is throughout small ; and on the third molar 

 connected by a ridge to the entoconid. The fourth premolar 

 is complex, the protoconid and deuteroconid being connected 

 by a ridge ; and there are two well-developed cusps behind on 

 the posterior rim. The third premolar is similar but lacks the 

 two posterior cusps. The upper molars are those typical of 

 the genus, with the cingulum well developed on the outside. 

 A distinct parastyle is formed on the anterior external angle 

 of the cingulum. The posterior intermediate is isolated while 

 the anterior one is connected to the protocone. 



The three lower molars measure together 16 mm . 26 speci- 

 mens were found along Bridger Cr., Wyoming. 



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