632 



course of the entocarotid canal may be traced on the right side. The fracture of the base of 

 the zygomatic process of the right squamosal shows the coarse osseous texture of its swollen 

 part. Behind the four normal molars there are two small shallow alveoli on each side, which 

 are so close together as to appear like the socket of a tooth with a bifid base. The lower jaw 

 has four molars on each side, but with the remnant of the socket of a much smaller tooth 

 anterior to the first of the left side. 



Hunterian. 



3865. The lower jaw of a large Walrus (Trichecus Rosmarus}. 



The fourth molar on each side appears to have been smaller than usual. 



Hunterian. 



3866. A mutilated cranium of a Walrus (Trichecm Rosmarus}, from which all the 

 teeth have been removed, together with the major part of the occipital bone. 



The entocranial part of the petrosal is depressed with an obtuse bifid apex, without any 

 cerebellar pit. The foramina lacera anteriora are remarkable for their very great size. The 

 base or roof of each socket of the canine has processes of bone projecting like stalactites into 

 the cavity. Anterior to the first of the four normal molar sockets, which, as above remarked, 

 is by its position an incisor, there is a smaller socket for another incisor in each premaxillary. 



Hunterian. 



3867. The cranium, in three transverse sections, of a large male Walrus (Trichecus 

 Rosmarus). 



The posterior section shows the density of the cranial walls, gradually degenerating into a 

 coarse cellular texture, in the enormous mastoids. It also shows the form and connections of 

 the bony tentorium, and the termination of the meatus auditorius, and the almost hemispheric, 

 smooth, tympanic cavities. The middle section shows the commencement of the eustachian 

 tubes from these cavities, the sella with the posterior clinoid ridge, the long chiasmal tract, 

 and the rhinencephalic fossa divided by the crista galli. The anterior section shows the area 

 of the large antorbital canal, and the shape of the nasal fossae, which contract as they pass 

 forwards to the vertical external nostril. Part of the large and complex turbinal is preserved 

 on the right side. 



Hunterian. 



3868. The skull, with the dried skin of the head, vertically and longitudinally bi- 

 sected, of a female Walrus (Trichecus Rosmarus}. 



This specimen shows the small vertical crescentic nostrils, and the still smaller apertures of 

 the eyelids, with the short thick bristles or their sockets on the upper lip. The septum 

 narium is preserved in the left half of the section : the osseous part is formed by the canali- 

 culate vomer and the coalesced plates of the prefrontals, dividing the posterior halves of the 

 olfactory chamber. The thick parietes of the skull show a coarse diploe. The lateral sinuses 

 are completely surrounded by bone. The course of the vein which perforates the back part 



