DAKOTA AND NEBRASKA. 59 



Inferior molars. — The first lower premolar oi Drepanodon primcevvs is proportion- 

 ately smaller in relation with the succeeding tooth than in Fells. Its crown is 

 trilobed, and is inserted by two fangs as in the latter. The thickness of the base 

 of the crown is nearly uniform. 



The second lower premolar repeats the form of the first, but is nearly twice as 

 large. 



The lower sectorial molar, besides the pair of broad trenchant lobes of the crown, 

 as in the cats, possesses a well-developed posterior basal heel or suli-lobe sub-divided 

 or notched at the middle. In this respect the tooth resembles the corresponding 

 tooth of Pseudcelurus intrepidus, from the Niobrara River. Neither the European 

 Drepanodon megantereon nor the D. neogcetcs of Brazil present such a development of 

 the sub-lobe. The angular valley between the principal lobes of the crown internally, 

 as in the corresponding valley of the upper sectorial molar, does not converge into a 

 fossa so consjjicuously as in the cats. This absence of the fossa in the sectorial molars 

 of D. primcevus appears to be due to the narrowness or lateral compression of the 

 crowns in comparison with those of the cats. 



The lower molar teeth are separated from the inferior canine by a much wider 

 hiatus proportionately than in the cats ; a difterence which probably relates to the 

 comparatively excessive development of the upper canines and the proportionate 

 reduction of the lower ones. 



Canines. — The upper canine teeth, from their remarkable size and form, are 

 characteristic of the genus of which Z>. primcevus forms a member. They descend 

 from their alveoli nearly parallel with each other, and not divergent as they are 

 represented to be in the great Brazilian Sabre-toothed Tiger, D. neogceus. Curving 

 forward, they descend behind the inferior canines and then behind the crested margin 

 of the chin, and in the unworn condition appear to have extended as far as the points 

 of the downward prolongations of the latter. 



The crown of the upper canines is laterally compressed, with the anterior and jdos- 

 terior borders at their lower part trenchant and finely serrulated. The anterior 

 border is trenchant and serrulated to within a few lines of the cessation of the enamel 

 investment of the crown. On the posterior border the serrulation does not reach 

 the latter position within nearly an inch. 



The fang of the upper canine curves upward and backward along the antero- 

 superior part of the maxillary bone. Its lower part is somewhat gibbous, producing 

 a convexity of the alveolus externally corresponding with that in a similar position in 

 the cats. 



The inferior canines, comparatively small teeth both in relation with those above 

 and with the homologous ones in Felis, project almost perpendicularly, with a slight 



