Cope.] 146 [Dec. 16, 



Testudinid^e. 

 a. Two anal scuta. 



Ten abdominal scuta .Hadrianus Cope. 



aa- One anal scutum. 



Lower jaw with two cutting edges Xerobates Agass. 



LoAver jaw with one cutting edge Testudo Linn. 



RODENTIA. 



Plesiarctomys btjccatus Cope. 

 Two mandibular rami. 

 Plesiarctomys delicattor Leidy. 



Mandibles of six individuals, some of them accompanied by bones of 

 the skeleton. 



BUNOTHERIA. 



T^ENIODONTA. 



Additional material gives the following results with regard to the 

 affinities of this sub-order. There are three allied groups represented by 

 the genera Esthonyx, Tillotherium and Calamodon of the American Eo- 

 cenes, which are equally unlike each other. Esthonyx, as I long since 

 showed, is related to the existing Erinaceus ; very nearly indeed, if the 

 dentition alone is considered. Its anterior incisor teeth are unusually 

 developed, and have, as in Erinaceus, long roots. One pair at least in the 

 lower jaw has enamel on the external face only, and enjoys a considerable 

 period of growth. The genus Tillotherium is (fide Marsh) quite near to 

 Esthonyx. Its molars and premolars are identical in character with those 

 of that genus, the only important difference being found in the incisors. 

 Here, one pair above, and one pair below, are faced with enamel in front 

 only, and grow from persistent pulps as in the Bodentia. This character 

 has been included by Marsh in those he ascribes to his "order" of Tillo- 

 dontia, but as he includes Esthonyx in that order,* which does not possess 

 the character, it is not very clear on what the supposed order reposes. The 

 rodent character of the incisors is the only one that I know of which dis- 

 tinguishes Tillotherium from the Inesctivora. I have on this account 

 retained the Tillodonta as a sub-order, and referred Esthonyx to the Insecti- 

 vora. 



The Tceniodonta agree with the Tillodonta in the possession of a pair of 

 inferior incisors of rodent character, but it adds several remarkable pecu- 

 liarities. Chief among these is the character of the inferior canines. In 

 the Tillodonta they are either wanting, as in Erinaceus, according to the 

 Cuvierian diagnosis, or they are insignificant. In Calamodon they are of 

 large size, and though not as long-rooted as the second incisors, grow from 

 presistent pulps. They have two enamel faces, the anterior and the 

 posterior, the former like the corresponding face of the rodent incisors. 



* Report of U. S. G. Survey 40th Parallel, toy Clarance King ; Vol. i, p. 377. 



