1881.] 1*T [Cope. 



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

 ter distinguishes Calamodon as a form as different from Tillotherium, as 

 the latter is from EstJwnyx. There are, however, other characters. The 

 external incisors, wanting in Tillotlierium, are here largely developed, and 

 though not growing from persistent 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 EstJwnyx, where 

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

 superior dentition of the Tceniodonta is yet unknown. 



Calamodon simplex Cope. 



Report Vertebrate Toss., New Mexico, U. Si Geog. Surv. W. of 100th 

 Mer. 1874, p. 5. Report of do. Capt. G. M. Wheeler, iv, ii, p. 166. 



A nearly complete mandible of this species was found by Mr. Wortman, 

 besides a series of unworn molar and canine teeth of a second individual, 

 and fragments of some others. These furnish the correct dental formula 

 as far as they go, as follows : I. 3 ; C. 1 ; M. 5. It appears that I correctly 

 referred the long rodent teeth to the lower incisior series, but that the 

 truncate two banded teeth so characteristic of the sub-order, are canines 

 and not incisors, and that they belong to the lower as well as probably to 

 the upper jaw. 



The characters of the incisors are very peculiar. The first are small 

 with short subcylindric crowns, and conic roots. The second incisors 

 have been described ; as in C. arcammms they have a horizontal shoulder 

 posterior to the base of the cutting portion. The third incisors increase 

 in diameter upwards, and have a triangular section. The largest side 

 of the triangle is interior, and the shortest the posterior, and neither 

 possess any enamel. The anterior or enamel faced side is slightly convex. 

 The grinding face is transverse and is in the plane of the corresponding 

 face of the canine. The long diameter of the crown of the canine is at 

 right angles to the anterior face of the third incisor, and diagonal to the 

 long axis of the mandibular ramus. This, with the peculiarities of the 

 other incisors, gives an irregular appearance to the anterior dentition. 



The five molars are very similar in character, and even those with un- 

 worn crowns do not present any distinction into premolars and true 

 molars. The enamel covers the summit of the crown, but on wearing, it 

 is soon reduced to a cylindrical sheath. Further wear brings the grinding 

 surface to the anterior and posterior surfaces which are covered with 

 cementum instead of enamel. 



Insectivoka. 



ESTHONYX BTJRMEISTERI Cope. 



Report Vertebrate Foss., New Mexico, 1874, p. 7. Report U. S. G. G. 

 Surv. "VV. of 100th Mer. G. M. Wheeler, iv, ii, p. 156, pi. xi, fig. 26. 



