680 



PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



SUMMARY. 



After obliterating- the numerous minor fissures and the branches of 

 the principal fissures from the cerebrum of the walrus there is left a i 

 very good fissural pattern resembling, in general, the typical arrange- 

 ment of the fissures in the brain of carnivorous animals. As in the ■ 

 cat, dog, and bear, the presylvian area is greater in length than the ■ 

 postsjdvian. In the sea lion the two areas are about equal. In Mon- 

 achus, (^allorhinus. and Phoca the postsylvian area is longer than the ■ 

 presylvian. 



The epiphysis is very highly developed in the walrus, and in the seals 

 it is much ))etter developed than in carnivora. The olfactory l)ul])s 

 and peduncles resemble those of the seals and do not attain as relatively 

 great development as in carnivora. The postrhinal resembles the con- 

 ditions in Zalophus, Callorhinus, and Monachus. The fissure postica 

 resembles that of Ursus, Zalophus, Callorhinus. and Phoca. The 

 supersylvian resembles that of the dog and bear. The postsupersyl- 

 vian is correlated more closelv with that of Zalophus than in any of 

 the other forms studied. The cctolateral, by fusing with the post- 

 superylvian, difiers from any of the other forms. The lateral fissure 

 corresponds with Zalophus in that it is relative!}" short. The ansate 

 fissure resembles the condition found in Zalophus, Ursus, and Canis. 

 The coronal is quite similar to that in Ursus and Zalophus. The 

 medilateral differs from that of the other forms in that it is interrupted; 

 if considered as a continuous fissure it would be the longest fissure of 

 the brain. The cruciate resembles the conditions found in Phoca and 

 Monachus. The splenial accords more closely with the conditions 

 found in Zalophus and Monachus. The marginal fissure resembles 

 that of Monachus; it is not especially well developed. The develop- 

 ment of the postcornu suggests a condition between that found in 

 Calloi'hinus on the one hand and Monachus on the other. 



As a matter of convenience, a tal)le of the more important regions 

 in the re))resentatives of the different groups examined is herewith 

 append(>d: 



