34G ON THE EXTINCT MAMMALIA OF 



name of Muste'la angnstifrons. Similar ridges, relatively less well developed, exist in 

 the Gray Fox. 



The orbits are as little distinct from the temporal fossa? as in the Skunk or the 

 European Hedgehog. The fossil retains most of the teeth, figures 25, 26, the num- 

 ber of which on each side consists .of seven molars, the canine, and two incisors. Of 

 the molars, the back four have broad trilateral crowns, with a number of points or 

 tubercles as in the Opossums and Hedgehogs, or the back two in the Dog. The ante- 

 rior three molars have simple laterally compressed conical crowns. The canines are 

 comparatively small. 



Whether the animal possessed a greater number of incisors in the upper jaw than 

 appears to be indicated in the fossil is somewhat uncertain, for although the specimen 

 is imperfect at the end of the snout, yet the alveolar border looks as if it were entire, 

 and even if it is not, the j^ortion lost would appear to be too small to accommodate 

 an additional j)air of teeth. 



Upper view of the skull. (Figure 27, plate XXVI.) — The cranium back of the 

 orbital spaces is conoidal and wider than high ; is feebly contracted back of the zygo- 

 matic arches, and then expanded to the acute border of the inion. It is narrowest 

 immediately back of the post-orbital prominences, but is relatively not so much con- 

 stricted as in the Mink or Fox, but more so than in the Skunk and European 

 Hedgehog. 



The ridges defining the upper part of the temporal fossae are prominent, thick, 

 linear and obtuse. They are nearly parallel, and extend from the inion to the fore- 

 head, where they swell in the lateral prominences common to the latter and the 

 post-orbital eminences. The extremities of the ridges are moderately divergent. 

 The intervening space forms a wide and nearly flat gutter from two and three-quar- 

 ter lines where narrowest to about four lines towards the ends. 



The forehead is of moderate width, prominently convex at the sides and depressed 

 at the middle. Laterally it is defined by the short, obtuse supra-orbital margin end- 

 ing in the post-orbital eminence. 



The face is long, and tapers evenly to the end of the snout. The nasals are long, 

 and of nearly uniform breadth. They commence together in a short obtuse angle. 

 Their anterior extremities are lost in the fossil. 



Lateral view. (Figure 25, plate XXVI.) — The upper outline of the skull forms an 

 almost unbroken curve. It slopes slightly downward at the posterior third, and 

 strongly and evenly so in front to the end of the face. The lateral border of the 

 inion inclines as little as m the OjDOSsum. The occipital condyles project but slightly 

 beyond it. 



The temporal fossa is small compared with its extent in most Carnivora, and has 



