SO PHYSIOLOGICAL SERIES. 



D. 79. The brain of a Shark, probably a species of Carcharias. 



The fore-part of this brain agrees in all important 

 particulars with the published descriptions of that of the 

 Blue Shark (Carcharias glaucus). The olfactory bulbs are 

 completely double, each part being attached to the olfactory 

 peduncle by a short separate stalk. The peduncles are long 

 and apparently solid, and terminate on either side in an oval 

 swelling upon the lateral parts of the cerebrum, far back 

 towards the ventral surface. The large and massive cere- 

 hriim shows no external sign of division upon its dorsal 

 a-peet., but beneath there is a slight median furrow. Pos- 

 teriorly it overhangs the thalamencephalon and meets the 

 anterior surface of the optic lobes. In other respects this 

 brain closely resembles that of Galena. 0. C. 1311 B. 



D. 80. A specimen of the brain of a Shark, with the medulla 

 removed. It is probable from the general form of the 

 cerebrum, and more particularly from the characteristic 

 method of origin of the olfactory peduncle (seen on the right), 

 that this is the brain of a Carcharias. It is strongly bent 

 artificially towards the ventral aspect, and a piece has 

 been removed from the left side of the cerebrum by trans- 

 verse and sagittal incisions, to show the immense thickness 

 of the dorsal cerebral wall and the relatively small size of the 

 ventricle. Upon the transverse sectional surface, a portion 

 of the choroid plexus can be seen protruding from the 

 vi-ntrieular cavity. The method of apposition of the medul- 

 lary auricles in the mid-line can be clearly seen beneath the 

 posterior lobe of the cerebellum. 0. C. 1311 A a. 



D. 81. The cranium of a Monk-fish (Rhina sguatina), with the 



brain in situ exposed from the dorsal and ventral aspects. 



The brain in this fish is remarkable for the slight develop- 



ni iit of the olfactory centres, for not only are the bulbs 



ami peduncles peculiarly small for an Elasmobranch, but the 



1 'nun U also feeble. The latter is thin-walled (so that 



it- apparent size is deceptive), with a pair of rounded 



in--* on its dorsal aspect, and is deeply cleft anteriorly 



a- in some of the lower Sharks. The low type of the brain 



is further -liown by its long narrow form ; and by the 



