350 NOTES ON THE CANIDiE OF THE WHITE RIVER OLIGOCENE. 



very large, forming an oval, with its long axis directed antero-posteriorly, in shape and 

 size agreeing much more closely with the condition found in the cats than Avith that of 

 the recent dogs. 



The femur (PL XX, Fig. 18) is stout, and long in proportion to the length of the 

 fore-limb bones, but not very long as compared with the size of the animal. While not 

 differing in any very marked fashion from the thigh-bone of Canis, it yet has some 

 resemblances to that of the felines. The small, hemispherical head is set upon a longer 

 neck than in recent dogs and has a smaller, deeper and more circular pit for the round 

 ligament, than in the latter. As in Canis, the head projects more obliquely upward and 

 less directly inward than in Felis. The great trochanter is large and has a very rugose 

 surface, but it has no such antero-posterior extension, does not rise so high and is not so 

 pointed as in the existing forms of Canddce. In consequence of this shape of the great 

 trochanter, the digital fossa is smaller and much shallower than in the cats or recent 

 dogs. From the great trochanter a sharp and prominent ridge, the linea aspera externa, 

 descends along the external border of the shaft. Whether a third trochanter was present 

 cannot yet be definitely determined, because in the only two femora preserved in the 

 collection, the outer edge of the shaft is broken away at the point where the third 

 trochanter would be, if present. In all probability, however, Daphcmus did possess this 

 trochanter, at least, in rudimentary form, as may be inferred from the analogy of the 

 sal ire-tooth Dinictis, and still more from the little contemporary dog, Cynodictis, which 

 in many respects approximates the structure of the modern Canidce more closely than 

 does Daphcmus. The lesser or second trochanter is larger, more prominent, and of more 

 decidedly conical shape than in the recent species of either Canis or Felis. 



The shaft of the femur is long, slender and nearly straight, though slightly arched 

 toward the dorsal or anterior side ; it differs from that of the modern dogs in its lesser 

 curvature, and in broadening and thickening more gradually toward the distal end, and 

 from that of the true eats in being more slender and of more nearly cylindrical 

 shape. The rotular trochlea is rather narrower transversely than in the true cats, 

 or even than in Dinictis, but is characterized by the same shallowness, and resembles 

 that of the latter genus in its shortness vertically and lack of prominence. Trans- 

 versely, the groove is but slightly concave, and it has much less prominent borders 

 than in the existing species of Canis; these borders are slightly asymmetrical, the external 

 one rising a little higher and being a trifle more prominent than the internal. A decided 

 difference from both Canis and Felis consists in the fact that the trochlea hardly projects 

 at all in front of the plane of the shaft, the anterior face of the latter gradually swelling 

 to the level of the groove. In both of the recent genera mentioned, and especially in the 

 canines, the trochlea projects prominently in advance of the shaft. 



