NOTES ON THE CANID.E OF THE WHITE RIVER OLIGOCENE. 363 



Miacis utntensis Osborn. 

 Bull. Am. Mus. Nat. Hist. N. ¥., Vol. vn, p. 77. 



Size rather less than that of D. hartshomianus ; upper sectorial relatively small and 

 tubercular molars large ; premolars short and thick. 



Measurements. 



MM. 



Length, pi to ni 5 - inclusive 37 



P 3 length 7 



PA length 11 



P* width 11 



M l length 11 



Mi -width 1G 



M i length 9 



M- 2 - width 7.5 



Fig. A. — First upper molar of the left side : 



1, of ? Miacis uintensis. 2, of Daphxnus harlsTiormanns. 3, of Canis lalrans. .r, cusp usually regarded as the 

 protocone. 



If Iliads be rightly regarded as having a place in the canine phylum, then the 

 structure of its upper tubercular molars is of great interest and will require a revis- 

 ion of the current views concerning the homologies of the cusps in the upper molars of 

 the dogs. In Canis, according to the usual interpretation, m A is composed of two external 

 cusps, the para- and metacones, and at the apex of the triangle of which the para- and 

 metacones form the base, an unpaired internal cusp, the protocone, with the proto- and 

 metaconules on the anterior and posterior sides of the triangle respectively. Internal 

 and somewhat posterior to the protocone is a large crescentic cusp, which is commonly 

 regarded as an enlargement of the cingulum, although in unworn teeth a faint cingulum 

 may be traced all around this crescentic cusp and is continuous with the prominent cin- 

 gulum which bounds the anterior wall of the crown. If this interpretation of the cusps 

 be correct, and further, if Miacis is ancestral to the Can idee, them m - 1 in the Uinta 

 genus is without a 'protocone and has only the para- and metacones, minute conules and 

 the large inner crescentic cusp. It seems much more rational to conclude that the lat- 

 ter is really the protocone and that the cusp which has been so named in Canis i^ an 

 additional element subsequently developed. In Dap/urn us this inner crescentic cusp and 



