422 E. S. GOODRICH. 



This fossil has never been figured before ; it was probably 

 obtained about 1875. The coronoid process and the condyle 

 have been broken ; there are eight consecutive teeth present — 

 five molars and three premolars. These teeth resemble in 

 every particular those of the foregoing specimen. 



The dental formula of this genus has hitherto been very 

 difficult to settle, but the working out of the new teeth and of 

 the sockets of the missing teeth has rendered the task easier. 



Owen, who only studied the York specimen, assigned to it 

 the formula i. 3, c. 1, pm. 6, m. 6 (23). He considered that 

 the tooth missing between the molars and premolars had been 

 a molar. In front he made out sockets for the three additional 

 premolars, the canine, and the incisors. However, these so- 

 called sockets were mere undulations of the edge of the matrix, 

 not corresponding to the true sockets which I have now exposed. 

 Mr. Lyddeker (12) gives the probable formula as i. 4, c. 1, 

 pm. 4, m. 7, which was adopted by Osborn in his first paper 

 (14). After personally examining the three specimens Osborn 

 gives the formula " with considerable certainty as follows : — 

 i. ? 3, c. 1, pm. 4, m. 6" (15). He tells us that " the Oxford 

 specimens show that there were but six molars instead of 



seven In fact, one .... specimen .... shows but 



five molars. If this specimen be adult, as seems improbable, 

 it may represent a new genus transitional between Amphilestes 

 with six molars and Triconodon with four'^ (15). I must con- 

 fess that I am quite unable to see how one specimen with five 

 molars and another with four (at that time) can even without 

 "certainty^' lead to the adoption of the formula m. 6. The 

 ingenious speculation as to the intermediate genus seems to be 

 quite unnecessary when we now know that all the existing 

 specimens possess five molars, and show no signs of having had 

 more or fewer. The premolars are more difficult to deal with. 

 If we measure the distance between the last molar^ and the 

 first premolar in the first and s.econd Oxford specimens we find 

 that the eight consecutive teeth occupy exactly the same space 



1 In these measurements I have found it convenient to measure from the 

 middle of one tooth to the middle of another. 



