676 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



the removal of the membranes and hardening in spirit." Brain A^j 

 weighed 24 ounces 7 drams avoirdupois; B 13i ounces, and C 26 ' 

 ounces. In the specimens examined by me only the larger of the two 

 brains was weighed, all of the membranes having been removed from 

 the cerebrum, but not from the cerebellum and the brain stem adja- 

 cent to it, the pia and arachnoid still adhering. The total weight of 1 

 the l)rain under these conditions was 29 ounces avoirdupois. The 

 weight of the cerebrum without the pia was 22f ounces, leaving a i 

 woiolit of ()i ounces for the cerebellum, oblongata, mesencephal, and I 

 epiphysis, the latter having adhered to the cerebellum. Turner has • 

 called attention to the remarka])lc size and leaf-like or pyriform shape 

 of the e])iphysis (pineal body) in the walrus, but does not mention its ■ 

 weight. Ill my specimen it weighed 1 dram, 1 scruple, and 3 grains, , 

 or a total of 88 grains. 



FISSURES AND GYRES. 



The olfactory tissure is scarcely represented; a slight, short depres- 

 sion at the attacinnent of the olfactory peduncle is all that can be found. 

 The olfactory bulbs were missing, but the peduncles have a])out the 

 same size as those in Callorhinus and Monachus, and are relatively 

 much smaller than in the bear. 



The rhinal tissure is well developed. The olfactory peduncle for 

 most of its length lies in this tissure. At the base of the peduncle 

 the rhinal sw^erves obliquely in a caudo-lateral direction and is lost in 

 the depths of the sylvian. It reaches a considerable depth under the 

 presj^lvian lobe (sub-operculum). 



The post rhinal is represented upon the ventral surface as a short 

 spur or outcrop of the submerged postica, resembling in this respect 

 the condition found in Zalophus, Callorhinus, and Monachus. In IJrsus 

 and Phoca the post rhinal i.s a continuation of the rhinal caudad of the 

 sylvian. 



Lat&i'ol aspect.— ^\i^ sylvian points in the usual dorso-caudal direc- 

 tion on the latei'al surface. It is a straight tissure, and does not bifur- 

 cate at its end. It measures 60 millimeters in length, and has a depth 

 ranging from 20 to 30 millimeters. It is the deepest fissure of the brain, 

 extending to within .5 millimeters of the lateral ventricle (paracade). On 

 opening the sylvian fissure one sees a fissure, the presupersylvian, quite 

 near the lateral surface of the hemicerebrum. The two fissures run 

 nearly parallel with each other, Init diverge dorsally where the presu- 

 persylvian becomes an ordinary surface tissure. From three to six minor 

 submerged fissures are found in the cephalic wall of the sylvian. These 

 pass upward toward the surface, and some have a superficial connec- 

 tion with the presupersylvian, but the majority usually do not appear 

 upon the lateral aspect of the brain. Submerged minor fissures also 

 appear in the caudal wall of the sylvian. These in general have the 



