368 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



narrow and deep. In Necrolestes the roots of the zygomata are normal 

 in character, and the arches curve upward more decidedly than in the ex- 

 isting genus, in which they are very slender and almost straight. The 

 glenoid cavity resembles that of the latter, but is somewhat larger and 

 more deeply concave. The tympanic bulla is ossified and moderately 

 inflated, though all the specimens are so damaged in this region of the 

 skull as to render this determination slightly uncertain. 



The sagittal crest is very inconspicuous but it is longer and more dis- 

 tinct than in Chrysochloris ; the occipital crest, on the other hand is a mere 

 raised line and is much less elevated than in the latter. The cranium has 

 not the straight, tapering tubular form characteristic of Chrysochloris, but 

 is broader and has a faintly marked postorbital constriction, which is more 

 distinct than in those species of Chrysochloris which possess it at all (C ruti- 

 lans, C. aured]. A very slight angulation of the frontal represents the 

 postorbital process, but it is hardly worthy of the name, and there is no 

 corresponding process on the jugal. 



The nasals are long and tapering and at their anterior ends they are 

 upturned in a curious fashion, so as to make their dorsal surfaces strongly 

 concave. Thinking at first that this appearance might, at least in part, be 

 due to distortion from pressure, I have examined with great care the 

 specimen which displays this character and have reached the conclusion 

 that the character is a natural one, though in a second individual it is not 

 apparent and even the prolongation of the muzzle is lacking. This latter 

 skull, however, has evidently been flattened by pressure normal to its 

 upper surface and the snout appears to have been broken off just in front 

 of the premaxillary alveoli, and although it is possible that a specific or 

 even a generic difference may here be indicated, yet the agreement of the 

 two specimens is otherwise so close and exact that such a difference does 

 not seem likely. The premaxillaries are elongate antero-posteriorly and 

 are completely fused in the median line. From the dorsal border of the 

 horizontal ramus arises a slender, pointed, median spike, which extends 

 obliquely upward and forward more than half way to the nasals and incom- 

 pletely divides the anterior nares into two distinct openings, which present 

 forward and very slightly downward. 



The maxillary is long and low and has a conspicuous preorbital prom- 

 inence, formed by the alveolus of the large canine ; in front of this swelling, 

 and made all the more obvious by the juxtaposition, is a deep constriction, 



