NOTES ON THE CANUTE OF THE WHITE RIVER OLIGOCENE. %'il 



transversely and antero-posteriorly than in most recent species of Cards. As in that 

 genus, the external incisor is much the largest tooth of the series, and forms with tin- 

 upper and lower canines a formidable lacerating apparatus. The diastema between the 

 incisors and the canine is somewhat greater than in Canis, and the premaxillary is quite 

 deeply constricted at that point, forming a groove for the reception of the lower canine. 



The canine is of the usual- compressed, oval section, but the compression is less 

 decided than in Canis, the longitudinal diameter not so greatly exceeding the transverse. 

 The fang of the canine is long and stout, producing a marked swelling upon the outer 

 face of the maxillary ; the crown is of only moderate length, but is both actually and 

 proportionately heavier than in the coyote (C. latrans). 



The premolars are notably small and simple ; they increase in size regularly from 

 the first to the fourth, the sectorial being, of course, much larger than any of the others. 

 The first premolar is implanted by a single fang, and has a small crown of compressed 

 conical shape, with much less conspicuous internal cingulum than in the recent species of 

 the Canidce. The second premolar is decidedly smaller than in most of the modern dogs, 

 and is separated by longer interspaces from both the preceding and the succeeding tooth ; 

 it has a low, pointed, simple and much compressed crown, without the small posterior 

 tubercles which are found in nearly all the recent species of the family. The third pre- 

 molar is much longer and especially has a higher crown than p ^, but has a similar shape, 

 without posterior basal tubercles, and, like p ^-, is inserted by two fangs. The sectorial (p i) 

 is very primitive in character, as compared with that of the typical recent species of 

 Canis. Certain modern members of the family, such as Otocyon and Canis corsac, for 

 example, have, it is true, even smaller and simpler sectorials than Daphanus, but as in 

 these forms this is doubtless due to a secondary simplification, they need not be drawn 

 into comparison. The primitive character of the sectorial in 'the White River genus is 

 shown in the thick, pyramidal shape of the antero-external cusp (protocone) which is less 

 compressed and trenchant than in the modern species, in the smaller size of the postero- 

 external cutting ridge (tritocone) and in the unreduced internal cusp (deuterocone) which 

 is very much larger and more prominent than in Canis, and is carried upon a larger 

 fang. The position of this inner cusp with reference to the protocone is the same as in 

 the recent genus. As a whole, the sectorial is small and gives to the dentition a decidedly 

 microdont character. 



The premolar series of the two sides diverge quite rapidly posteriorly, each tooth, 

 except p i, being oblique in position, with reference to the long axis of the skull, thus 

 giving the bony palate its greatest width at the hinder edge of the sectorials. The 

 obliquity of the teeth and their divergence posteriorly are even more strongly marked 

 than in most recent dogs. 



a. p. s. — VOL. XIX. 2 p. 



