370 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



The condylar and carotid foramina are not displayed in any of the speci- 

 mens. The foramen ovale is very large, more conspicuous than in the 

 modern genus and is more widely separated from the "large opening 

 which includes the sphenoidal fissure, foramen rotundum, and optic fora- 

 men," for Dobson's description ('83) seems to apply to Necrolestes also. 

 This opening is, however, considerably farther forward than in Chryso- 

 chloris. The infraorbital foramen is larger and covered by a much heavier 

 bony process than in the latter and the lachrymal foramen is also larger, 

 but occupies a similar position. 



That the skull of Necrolestes is of the same type as that of Chrysochloris 

 will be sufficiently obvious from the foregoing description, and although 

 there are many differences between them, these differences are not greater 

 than may often be found within the limits of a single family. In most re- 

 spects, as would be anticipated, Necrolestes has the more primitive skull, 

 as is especially to be seen in the uninflated squamosals, in the presence 

 of a slight interorbital constriction, and in the undiminished strength of 

 the zygomatic arches and the normal shape of their roots and the reten- 

 tion of the masseteric fossa of the mandible. On the other hand, the re- 

 markable, prolonged and upturned snout would seem to be a specialization 

 in the fossil, though the lateral processes of the premaxillaries and the 

 small median anterior spines arising from the horizontal rami in Chryso- 

 chloris suggest that in the ancestor of that genus the muzzle may have 

 once been much longer than in its existing representatives. In Notoryctes 

 the skull is of a different structural type ; the occiput is vertical and flat- 

 tened ; the face is very broad at the orbits, contracting abruptly into the 

 short, blunt muzzle. The auditory bulla is extensively open and is partly 

 made up of the alisphenoid, while the angle of the mandible is very dis- 

 tinctly inflected. In brief, the skull of Notoryctes is in all essentials mar- 

 supial, while those of Chrysochloris and Necrolestes are as distinctively 

 insectivorous. 



The Vertebral Column. None of the specimens is sufficiently well pre- 

 served to make the vertebral formula apparent, although vertebrae from 

 all the regions of the column are represented, most of them belonging to 

 a single individual. The cervical vertebrae are very much like those of 

 Chrysochloris; they have short, broad, depressed centra, without hypa- 

 pophyses, and very slender neural arches, though some, at least, possess 

 fairly well developed neural spines, while in the modern genus only the 



