58 



mens, it shows a distinct proximal ganglion against the base of the 

 brain, and a smaller distal one near the base of the base of the bulbus. 

 The ganglia vary somewhat in position, and, sometimes, as has been 

 observed in other Selachians, there will be clusters of ganglion - cells 

 making varicosities along the nerve. I did not observe branches of 

 the nerve in front of the ganglion. The nerve is slender and passes 

 directly to the lateral division of the olfactory nerve with which it 

 unites. 



Id Sphyrna tiburo. — A part of the brain of the bonnet- 

 head shark is represented in Fig. 22. The prosencephalon is expanded 



Fig. 22. Slightly reduced view of the fore-brain and olfactory cups of an adult 

 Sphyrna tiburo. Also similar view from the ventral side. 



laterally, but is short antero - posteriorly. The olfactory cups are 

 elongated and shaped somewhat like a long seed -pod. The tractus 

 is relatively slender. 



The new nerve (Fig. 22 B n. nov.) connects with the brain on the 

 ventral surface, in a depression much nearer the optic nerve than in 

 the other forms described. From this point, the nerve passes directly 

 to the base of the bulbus, where it forks into two slender branches 

 which join the fila olfactoria, in a manner 1 was unable to make out 

 clearly in the single specimen of this shark at my command. 



