1 882.] Geology and Paleontology. 685 



the outline is regular on each side, and the posterior extremity is 

 rounded. There are seven tubercles in the external row, five in 

 the middle row and only two in the internal, since the middle row 

 forms the internal edge of more than half the length of the 

 crown. No cingula. 



Measurements. — Length of M. 1, m. .0225 ; width of M. 1 at 

 middle, .0100. Length of M. 11, .0140 ; width of M. 11 anteriorly, 

 .0115. Besides the three rowed tubercles of the first molar, and 

 the apparent absence of the fourth premolars, this species differs 

 from the Catopsalis pollux in the large size and the larger number 

 of tubercles in each row of the molars. New Mexieo, D. Baldwin. 



Catopsalis pollux, sp. nov. — The size of this species exceeded 

 that of Macropus gigautcus and still more that of the Catopsalis 

 foliatus. The ramus has the form of that of a rodent, being ver- 

 tically narrowed at the diastema, and deep at the molar region. 

 The inferior face widens and becomes flat posteriorly, and is more 

 oblique than in the C. foliatus, from the greater downward exten- 

 sion of the external or masseteric edge. The interior edge on 

 the contrary, ascends a little from the anterior inferior border, 

 enclosing the large internal pterygoid fossa. The inferior plane 

 commences below the anterior part of the first true molar. The 

 symphysis is short, and was not probably strongly united, as in- 

 dicated by the few rugosities of its surface. The coronoid pro- 

 cess rises from a point opposite the posterior extremity of the 

 first true molar. 



The incisor is relatively large, and is more curved than that of 

 a kangaroo, having the general form of that of a rodent. The 

 acumination or bevel of the posterior face is less rapid than that 

 of a rodent, and is perfectly gradual. The enamel band covers 

 the antero-external face as far as exposed, which is to below the 

 anterior part of the diastema, and is gently convex in transverse 

 section. It does not cover the entire external face, as its width 

 »s equal, while the antero-posterior diameter of the tooth increases 

 below. The posterior face is convex and is not much narrowed. 

 The internal face is slightly concave, and the enamel is recurved 

 so as to form a band on its anterior part, thus differing from 

 most rodents. The enamel surface is delicately obsoletely line- 

 ndged. The length of the diastema is equal to that of the com- 

 bined P.-m. iv and M. 1. The fourth premolar is a simple tooth 

 With a triangular transverse section, the obtuse apex of the triangle 

 looking forward. This edge is continued downwards by reason 

 of the exposure of the anterior root, and is not acute. The first 

 true molar is an elongate-oval, with six tubercles on each side. 

 These are so closely placed that their outlines are angular, and 

 they are only separated by fissures. No cingula. The second 

 true molar is three-fifths the length of the first, and is broadly 

 rounded posteriorly. It supports four tubercles on the internal, 

 and five on the external sides, and a raised edge connecting the 



