6 HiCKSON, specimen of Ostcocella scptentrionalis {Gray). 



These " radial " canals are on the ventral side of the 

 rachis, and do not therefore correspond in position with 



7-'\ 



Figs. I and 2 — Uiagiams of a transverse section 

 through the rachis of Osteocella {Fig. \) and 

 Virgil laria (Fig. 2). A, the axis. /?, the dorsal, 

 longitudinal vessel. A^, the network of canals in 

 the mesoglcea. /', the position of the pinna; as 

 seen in a transverse section. A', the radial vessels 

 opening into the ventral canal in Osteocella, and 

 into the dorsal canal in Viigiilaria. V, the ventral 

 longitudinal canal. 



the " radial " canals of Virgnlaria and Halisce/'fmiji, which, 

 are on the dorsal side of the rachis. 



