47 



more direct than in Squalus. The peripheral end of the nerve is very 

 slender. Just before entering the fissure separating the two divisions 

 of the olfactory nerve, it branches unequally. One very fine branch 

 joins the median division of the olfactory nerve, and the central main 

 stem, which in reality is very slender, dips into the fissure and gives 



ms'ence 



Fig. 11. Fig. 12. 



Fig. 11. Dorsal view of the brain of Heptauchus ciuereus, nat. size. Eefereuce 

 marks as in previous figs. 



Fig. 12. Dorsal view of the brain of Hexanchus griseus, nat. size. 



off branches which mingle with those of the lateral division of the 

 olfactory nerve. 



The central terminations and peripheral distribution have not been 

 worked out in Heptanchus. 



In Hexanchus griseus. — Fig. 12 shows a sketch, natural size, 

 of the brain of the primitive form Hexanchus. The brain is relatively 



