[CARNIVORA]
SINOPA, Leidy.
A genus of small carnivorous animals, which Dr. Leidy regards as intermediate between the recent Canis and the extinct Hyænodon. Owing to the fragmentary condition of the remains found, no satisfactory generic definition has been given.
From the portion in our collection, we are able to throw some further light upon the genus, summing up the generic characteristics thus: Small carnivores, which have the last upper premolar as sectorial (thus differing from Hyænodon), the other premolars simple and conical.
The sectorial is shorter, antero-posteriorly, than the preceding tooth; has a short blade of a single lobe, and a large cusp developed from the posterior part; a cingulum surrounds the entire crown. The lower sectorial has the blade of a single lobe, and with a short heel.
Sinopa rapax, Leidy.
Proceedings of Ac. Nat. Sc., 1871, p. 115.
In addition to the molars of the lower jaw, described by Dr. Leidy we have what corresponds to the third and fourth premolars of the fox, their dental formulas being probably the same.
The third premolar is small and pointed; differing from the corresponding tooth in the fox, (1) in its being less compressed, (2) in its shorter antero-posterior diameter, (3) in the straighter and more nearly equal margins, and in (4) the absence of a posterior heel.
The tooth is inserted by two fangs, as in Canis and Hyænodon. The posterior shows a rudiment of a third, which is connate with its entire length above the alveolus. There is an indistinct cingulum around the entire crown.