64 THE MAMMALIA OF THE DEEP RIVER BEDS. 



second are of nearly equal size, "while the third is somewhat larger, though the differ- 

 ence is much less marked than in C. latrans or even than in the John Day species, 

 Temnocyon coryphaeus ; the teeth are crowded together, not spaced apart as in the 

 latter species. The diastema between the external incisor and the canine is rather 

 short. The latter is as well developed, relatively, as in the coyote, but of a some- 

 what different form, being more oval and less compressed in section; the depression 

 on the inner face and its anterior bounding ridge of enamel are also less marked. 



Except for their relative shortness (antero-posteriorly) and height, the premolars 

 closely resemble those of the modern species. PJ. is a very small and simple tooth, 

 implanted by a single fang; the crown is of compressed conical shape, without pos- 

 terior cingulnm. PJ2 is much larger, though small as compared with the same tooth 

 in C. latrans ; it is of elongated, compressed, conical form, but has no posterior basal 

 cusp (tritocone) such as occurs in the coyote. P-J3 is a still larger tooth of similar 

 construction, except that a small tritocone and posterior cingulum have been added, 

 which, however, are less conspicuous than in C. latrans. The sectorial (m) differs 

 but little in any respect from that of the existing microdont species of Canis ; the 

 protocone exceeds the tritocone less in antero-posterior extent than in the co3 T ote, and 

 the deuterocone is much more distinctly developed than in that species, so that the 

 transverse diameter of the crown is greater, not only in proportion to the antero-pos- 

 terior diameter (length) and to the size of the whole skull, but actually as well. In 

 some recent species of Canis, however, the deuterocone is quite as well developed. 

 The premolars are quite closely crowded together and set obliquely to the line of the 

 alveolus, so as to slightly overlap one another; posteriorly, the two lines of premolars 

 diverge quite rapidly, while the molars converge, so that the angulation between the 

 two series is very marked. 



The first molar is wider proportionately to its fore and aft length than in C. 

 latrans, and the external cusps, para- and metacones are lower, more conical, and less 

 angulate and pyramidal in shape than in the coyote. The cingulum is very strongly 

 developed at the antero-external angle of the crown, so as almost to deserve the name 

 of a parastyle, while it becomes very faintly marked upon the metacone. The inner 

 elements of the crown, the protocone and crescentic cingulum, are not nearly so 

 prominent as in the coyote ; the anterior conule is slightly better developed, and the 

 posterior distinctly less so, than in that animal. M. 2 is much reduced; the external 

 cingulum is faintly marked, except on the paracone, and the internal one not nearly 

 so strongly developed as in Canis latrans. 



B. Lower Jaw. The incisors are very small and set closely together, and, as is 

 usual in the dogs, the second pair are crowded back out of line with the others ; in 



