NERVES OF THE DOGFISH 



311 



terior to the cerebellar stalk, and ventral to the cerebellar crest 

 (figs. 18 and 24). _ At its decussation in the velum it becomes 

 closely associated j with other fiber tracts: the decussatio veli, 

 the tractus tectocerebellaris, and the radix mesencephalica tri- 

 gemini. ^jThe relations of these various tracts to each other have 



been described by Johnston ('05, '09) and by van Valkenburg 

 ('11) in Scyllium canicula and stellare. As stated by these 

 authors, the relations in Squalus acanthias (Acanthias vulgaris) 

 are essentially similar to those in Scyllium. From the decus- 

 sation the trochlearis fibers pass anteroventrally around the 

 lateral angle of the fourth ventricle to their origin in the troch- 



