THE MAMMALIA OP THE DEEP RIVER BEDS. 163 



Cyclopidius incisivus Scott. 



Amer. Naluraliit, 1893, p. 661. 



This species might with almost equal propriety be referred to Leptauchenia, 

 since it is, in many respects, a connecting link between the two genera; it is much 

 like C. simus, on the one hand, and L. decora of the "White River beds on the 

 other. It differs from the latter species principally in the much more reduced incisor 

 teeth aud in the larger premolars, and from the former in the presence of two incisors 

 in the premaxillary, the larger upper canine and premolar teeth and in details of 

 skull construction. As in all the species of Leptauchenia, the infraorbital foramen 

 is very small and placed above p-j). The upper incisors, two in number, are extremely 

 small, especially the median one, which is hardly more than a rudiment; the second 

 incisor is almost twice the width of the first and has an obliquely truncate cutting 

 edge. The two incisors of each side are implanted very close together, the first 

 somewhat overlapping the second, while a considerable gap separates the median 

 pair. The canine is larger than in the typical species of the genus, though this 

 character may be sexual, and is followed by a short though distinct diastema, which 

 about equals the fore-and-aft diameter of the canine. The premolars increase in 

 size posteriorly. The first is very small and simple; p^2 has a low internal ridge 

 representing the deuterocone, which in pJ) becomes very distinct and is connected by 

 a ridge with the postero-external angle of the crown, the valley opening in front. 

 The first three premolars have convex external faces, and are so inserted as to pro- 

 ject slightly backward as well as downward. The molars increase in antero-posterior 

 diameter from the first to the third, m. 8 markedly exceeding m. a in this dimension, as 

 the latter exceeds m. 1 ; in transverse width, however, m. 3 is the least of the series 

 and has much the highest crown. 



The nasals are more expanded anteriorly at their junction with the maxillaries 

 than even in Leptauchenia decora. The nasal opening is terminal, presenting ante- 

 riorly, and is of heart-like shape, with the apex downward. The premaxillae are of 

 somewhat peculiar form; the alveolar portion is insignificant, but the ascending 

 rami form quite a high symphysis and present their broad surfaces anteriorly, while 

 the superior expansions are twisted, so as to present laterally. The palate is long, 

 broad, and concave from side to side, the two molar series being almost parallel, 

 while the premolars converge anteriorly. The palate is carried farther behind the 

 last molar than in L. decora and, compared with that species, the posterior nares have 

 been shifted backward. The incisive foramina are very small and anterior in position. 



