BRAIN OF HAIR SEAL. 29 



The cruciate, unlike that of Gallorhinus, is represented upon both the mesal and 

 dorsal aspects. On the left hemicerebrum a shallow is present in the dorsal portion 

 not far from the margin. No distinct "ursine lozenge" is present here as in Gallor- 

 hinus. The foreshortened condition of this region may have something to do with its 

 absence. 



A well-defined postcruciate fissure is present on the left side. It presents a zygal 

 (Wilder) or quadriradiate form. A slight secondary fissure near the olfactory bulb may 

 represent a rudimentary precruciate fissure. 



The superorbital fissure shows a better development than in Gallorhinus and, 

 similarly, has no connection with the rhinal. But the opposite end, dissimilarly, 

 extends farther and is overlapped by the olfactory bulb. 



The medilateral is not present in Phoca as a distinct fissure. Its location is 

 occupied by a series of short, disconnected fissures. 



The coronal fissure is a relatively longer fissure than in Gallorhinus, but is not so 

 entirely disconnected from adjacent fissures. Its dorsal end lies caudal to the cruci- 

 ate. On the left hemicerebrum it is separated by a shallow from an apparant con- 

 nection with a continuation of the cephalic branch of the supersylvian. On the right 

 hemicerebrum the shallow is suggested by the interlocking at this point of two sub- 

 merged buttresses. 



The ansate fissure, while not distinctly represented as an independent fissure, 

 would, it seems to me, be indicated by the fissure extending from the coronal to the 

 cephalic branch of the supersylvian, where, on each hemicerebrum, the interlocking 

 of submerged buttresses would again suggest a shallow shutting it off from the branch 

 of the supersylvian, and then continuing to the lateral fissure, where a slight spur 

 pointing toward the intercerebral might indicate its separation from the lateral. 

 Owen in his figure of the hemicerebrum of Phoca represents a corresponding fissure as 

 the coronal. 



MESAI^ ASPECT. 



There is a slight appearance of the callosal fissure in the splenial half of the cal- 

 losum, but none at all for the remaining half. 



The hippocampal fissure is well developed and needs no special comment. 



The splenial fissure is well developed and in general is as described for Gallorhinus, 

 except that its position is farther removed from the frontal portion of the cerebrum 

 and that its cephalic end cuts the margin and is shown upon the dorsal surface. The 

 postsplenial has about the same relations as in Gallorhinus. 



The suUimiea fissura of Kukenthal' is poorly represented in my specimen of 

 Phoca, and is somewhat confused with smaller branches and secondary fissures. It 

 lies between the splenial and the callosum. Kiikenthal finds this fissure also present 

 in Phoca groenlandica, Phoca barbata, Macrorhinus leoninus, and Otaria jubata. In 

 Gallorhinus there was no appearance of this fissure whatever. The fissura sublimica 

 anterior of the same author is more clearly represented. In my former paper, on 

 account of its position dorsal to the callosum, I designated it questioningly as the 

 super callosal. On the left hemicerebrum it is well developed and connects with the 

 craciate. On the right side, however, the fissure is independent and much smaller. 

 In addition to this fissure, on each hemicerebrum, there is another dorsal to it and in 

 front of the splenial. In Gallorhinus I have called it the presplenial. 



' Untersuchungen an Walthieren, 1889. 



