General Notes. [January, 



the T^niodonta. — Additional material 

 suits with regard to the affinities of this 

 suborder. There are three allied groups represented by the 

 genera Esthonyx, Tillotherium and Calamodon of the American 

 Eocenes which are equally unlike each other. Esthonyx, as I 

 long since showed, is related to the existing Erinacens ; very near- 

 ly indeed if the dentition alone be 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 Rodentia. This 

 character has been included by Marsh in those he ascribes to his 

 " order " of Tillodontia, but as he includes Esthonyx in that order, 1 

 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 I know of which distinguishes Tillotherium from 

 the Insectivora. I have on this account retained the Tillodonta as 

 a suborder, and referred Esthonyx to the Insectivora. 



The Tamiodonta agree with the Tillodonta in the possession of 

 a pair of inferior incisors of rodent character, but it adds several 

 remarkable peculiarities. 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 persistent 

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

 the former like the corresponding face of the rodent incisors. 

 The function of the adult crown is that of a grinding tooth. This 

 character distinguishes Calamodon as a form as different from 

 Tillotherium, as the latter is from Esthonyx. There are, however, 

 other characters. The external incisors, wanting in Tillotherium, 

 are here largely developed, and though not growing from persist- 

 ent pulps have but one, an external band-like enamel face. Their 

 function is also that of grinders. The fact that the rodent teeth 

 in the lower jaw are the second incisors, renders it probable that 

 those of the Tillodonta hold the same position in the jaw. This 

 is to be anticipated from the arrangement in Esthonyx, where the 

 second inferior incisors are much larger than the first and third. 

 The superior dentition of the Teniodonta is unknown. There 

 are two families, the Ectoganida with two species, and the Cala- 

 modontidcB with five species. — E. D. Cope. 



1 Report of U. S. Geol. Survey 40th Parallel by Clarence King, Vol. (. p. 377.. 



