52 



glion the uerve passes on to the rather stout tractus, and, before 

 reaching the base of the bulbus, forks into two branches as shown in 

 the figure. These are distributed to the median and lateral parts of 

 the olfactory cup. 



Sections of the ganglia show the presence of a number of rela- 

 tively large ganglion cells. They are large as compared with those of 

 Squalus (Fig. 2 A) but smaller than those of Alopias (Fig. 2B). 



The condition of the new nerve is entirely similar in Trygon vio- 

 lacea. The lower sketch in Fig. 16 shows the usual position of the 

 ganglion (gn) before dissection, as seen from the ventral aspect. 



,^.^ In Myliobatisbovina. — 



, '^^^'^' ^ '' ^^^^^^^ J^^ The brain of Myliobatis, as of Try- 



■ "^ "^^^ ~^ - --'^ ^; gon, is of the condensed type. 



The cerebellum, overlying the mid- 

 ./ brain, comes into contact with the 

 thalamencephalon. 



The new nerve is extremely 

 difficult to expose in this form; 

 the ganglion lies wedged within 

 the angle between tractus and 

 prosencephalon and can not be 

 detected from surface view. So 

 tightly is it packed in this po- 

 sition, that it is folded upon it- 

 self, and requires very delicate 

 emx. manipulation to remove it. Al- 

 though looking expressly for this 

 nerve, I missed it in my first 

 three dissections of Myliobatis, 

 After the ganglion is freedby dis- 

 section from its position it shows 

 very clearly. It is filiform and 

 bent as shown in Fig. 17. The 

 nerve is joined to the anterior 

 ■r.. ,n T. 1 • Ü xu 1, • . dorsal surface of the prosence- 



lig. 17. Dorsal view of the brain of ^ 



an andult Myliobatis bovina, nat. size. phalou by tWO short rOOtS. 



In front of the ganglion, the 

 nerve is not free as in most forms, but lies on the tractus under a 

 close investment of connective tissue. It can be dissected free for 

 about three-fourths the length of the tractus, and then, after branching, 

 it hurries itself among the bundles of the tractus, and is with difficulty 



