Cope.] 4bb jOct. 20, 



opposite the posterior inner, but is anterior to such a position and inter- 

 mediate between the latter point, and the one occupied by the median 

 tubercle in P. rhahdodon. It is as large as the anterior external tubercle. 

 All these tubercles are conical, and not connected by angles or ridges. 

 The posterior external cusp leaves the cingulum wide posteriorly, and its 

 edge develops some small tubercles. There are also some small tubercles 

 at other points on the edge of the crown, but no other cingula. The 

 enamel is not regularly ridged as in P. rhabdodou, but has a rather coarse 

 obsolete wrinkling. 



Measurements. M. 



Length from P-m. ii to M ii inclusive 052 



Diameters of M.ii | anteroposterior Oil 



t. transverse 010 



Depth of ramus at M. ii 022 



Widthof " " 016 



Depthof " " P-m. ii 019 



From the Puerco formation of New Mexico, D. Baldwin, discoverer. 

 Haploconus Uneatus Cope, Amer. Nat. 1882, p. 417. 

 HaploGonus angustus Cope, Loc. cit. 1882, p. 418. Mioclcenus ang^istus 

 Cope, loc. cit. 1881, p. 831. 



Haploconus xiphodon, sp. nov. 



This species is represented by a mandibular ramus, and perhaps bj' three 

 rami. The one on which the species rests contains five molars, the middle 

 one of the series broken, so that its form cannot be positively ascertained. 

 It is probable that it is the first true molar, so that the animal exhibits the 

 last true molar not entirely protruded, and is therefore nearly adult, but 

 there are some reasons for suspecting it to be young. Thus the last inferior 

 molar does not exhibit more of a heel than the second usually does, and 

 the third supposed premolar is smaller than that tooth is in the other spe- 

 cies, having nearly the proportions of the second premolar. The teeth 

 present may then be supposed to be the molars from the second 

 to the sixth inclusive. But opposed to this view is the fact that the sup- 

 posed third premolar has more the structure of that tooth in details, than 

 that of the second, and the specimens accompanying, which have the tem- 

 porary dentition apparently of the same species, present premolar teeth of 

 a very different character. In any case the present specimen represents a 

 third species of the genus, and I describe it at present as an adult. 



The thiril premolar has a simple compressed crown, about as high as the 

 length of its base, and without anterior basal tubercle. It has a narrow 

 triangular posterior face which is concave, and truncated by a cingulum 

 below ; no heel proper, nor lateral cingula. The fourth premolar is an 

 elongate tooth consisting of a compressed principal median lobe, an ante- 

 rior lobe connected with it, and a heel. The latter has elevated posterior 

 and interior borders. A rudiment of an exterior border is seen in a narrow 



