80 



ZOOLOGY OF THE VOYAGE OF THE BEAGLE 





ridge continued obliquely upwards from above the upper edge of the petrous bone, 

 that the cerebellum has been situated wholly behind the cerebrum ; we learn also 

 from the same structure of the enduring parts that these perishable masses were not 

 divided, as in the Manis, by a bony septum, but by a membraneous tentorium, as in 

 the Glossothere and Armadillos : in the Orycteropus, as has been before remarked, 

 there is a strong, sharp, bony ridge extending into each side of the tentorium. 

 The vertical diameter of the cerebellum and medulla oblongata equals that of 

 the cerebrum, and is two inches three lines : the transverse diameter of the cerebel- 

 lum was about three inches nine lines; its anteroposterior extent about one inch 

 and a half. The sculpturing of the internal surface of the cranial cavity bespeaks 

 the high vascularity of the soft parts which it contained, and there are evident 

 indications that the upper and lateral surfaces of the brain had been disposed in a 

 few simple parallel longitudinal convolutions. The two anterior condyloid fora- 

 mina (m) have the same relative position as the single corresponding foramen in 

 the Glossothere, Orycterope, and Armadillos, and the inner surface of the skull 

 slopes outwards from these foramina to the inner margin of the occipital condyle. 



Of the bones of the face there remain only portions of the malar, lachrymal, 

 palatine, and maxillaries. The chief peculiarities of the malar bone have been 

 already noticed : the breadth of the base of the descending masseteric processes is 

 two inches two lines; its termination is broken off: the length of the ascending 

 post-orbital process of the malar cannot be determined from the same cause, but 

 it is fortunate that sufficient of this part of the cranium should have been 

 preserved to give this evidence of the affinities of the Scelidothere to the 

 Megathere. The malar bone is continued anteriorly, in a regular curve forwards 

 and upwards, to the lachrymal bone, and completes, with it, the anterior boundary 

 of the orbit : the size of the orbit is relatively smaller than in the Orycterope, and 

 still less than in the Ant-eaters : here, however, we have merely an exemplification 

 of the general law which regulates the relative size of the eye to the body in the 

 mammalia. The malar bone does not extend so far forwards in front of the orbit 

 as in either the Orycterope or Armadillo ; in the inclination, however, with which 

 the sides of the face converge forwards from the orbits, the Scelidothere holds an 

 intermediate place between the Armadillos and Orycterope. 



The lachrymal bone does not extend so far upon the face in the Scelidothere 

 as in the Orycterope; in which respect the Scelidothere resembles more the Mega- 

 there. The foramen for the exit of the infra-orbital nerve has the same situation near 

 the orbit as in the Megathere; its absolute distance from the anterior border of the 

 orbit is only half that in the Orycterope. The foramen is single in the Scelidothere, 

 as in the Orycterope ; in the Megathere there are two or three antorbital foramina. 

 The vertical diameter of this foramen is eight lines, the transverse diameter four 

 lines. So much of the outer surface of the superior maxillary bones as has been pre- 



