398 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



heretofore known to occur in America. Should the Hystrix venustus of 

 Leidy prove to really belong to the true Hystrh'incB, it brings this group 

 for the first time into the North American fauna. 



The other species of extinct Porcupine was described by Professor 

 Cope 1 from teeth found in the Port Kennedy bone-cave, under the name 

 of Erethizon cloacinum. 



ERETHIZON CLOACINUS Cope. 



Erethizon cloacinum Cope, Proc. Amer. Phil. Sou., xii, 1671, 93, fig. 19. 



This species is described from "a last superior molar of the left side 

 and a portion of one of the inferior incisors". The molar tooth is represented 

 as differing from the corresponding tooth of Erethizon dorsatus in two im- 

 portant particulars: "One of these is the greater vertical depth of the 

 external inflection of enamel", which " is nearly as deep as the internal, while 

 in E. dorsatum it is much shallower, the internal extending down to the 

 alveolar border." This, however, is a feature which I find to be very variable 

 in E. dorsatus, sometimes presenting just the appearance claimed to charac- 

 terize E. cloacinus. The other character is the possession of two enamel 

 islands, or annuli, in the posterior half of the triturating surface, while only 

 one occurs in any of the large series of specimens of E. dorsatus now before 

 ine. "The size of the teeth in E.cloacinumP says Professor Cope, " are about 

 equal to the largest seen in the E. dorsatum." The specimens were found 

 associated with the remains of different species of Megaloriijr, Myludon, 

 Mastodon, Tapirus, Ursus, Meleagris, several species of extinct Colcoplera, etc., 

 with which were mingled those of Lepus sylvaticus, a Squirrel closely allied 

 to Sciurus hudsonius, and several extinct species of A rvicola. 



