Marsh Collection^ Peabody Museum. 209 



has had no very definite standing. Its relationship to the 

 Primates, even, has been called in question, and it has been 

 thought by some to belong to the Rodentia. There are, how- 

 ever, about ten individuals represented in the Marsh collection, 

 which I do not hesitate to refer to Leidy's genus and species. 

 The most conclusive point in this identification is found in the 

 extra cusp on the inner posterior surface of the trigon of the 

 lower molars, the remains of which can be still plainly seen 

 in the much-worn molars of Leidy's type. In one specimen in 

 the Marsh collection, there is in association with the lower teeth 

 a fragment of an upper jaw containing two molars, so that 

 the structure of the teeth can be made out with a reasonable 

 degree of accuracy. 



The complete dental formula of the lower jaw is not known 

 with absolute certainty, but in one specimen the front of the 

 jaw is sufficiently preserved to render it highly probable that 

 there was but a single pair of incisors. At all events, if the 



142 



Figure 142. — Right lower jaw of Washakius insignis Leidy ; side view ; 

 two and one-half tiines natural size ; drawn from two specimens. 



middle incisors were present they must have been exceedingly 

 small. A good idea of the relations of the lower teeth can be had 

 from the accompanying^ illustration, figure 142, which was 

 drawn from two specimens. The outer side of the front of the 

 jaw is injured so that the lower part only of the alveolus for 

 the incisor is shown ; this is seen to be smaller than that for 

 the canine. Following this without diastema is a small alveo- 

 lus for the second premolar, after which come the double- 

 rooted third and fourth premolars. The crown of the second, 

 figure 143, has a simple pointed summit, to which is added a 

 small anterior basal, and a stronger internal cusp. That of the 

 second has a similar structure but the internal cusp is better 

 developed. In both the third and fourth premolars, the 

 internal cusp is placed rather low upon the crown. The heel 

 is rudimental. 



The molars are peculiar in the composition of their crowns, 

 by reason of the possession of an extra cusp situated internal 

 and a little posterior to the main antero-internal cusp. The 

 trigon thus has four cusps, a condition unknown in any other 

 species of Primate. The remaining cusps of the trigon are 



