EXPLANATION OF TEXT FIGURES. 



TEXT FIGURES 1—4. 



A\ a?—a^, first, second etc. arm. 



An. anus. 



Ca. caecum. 



G.G. cerebral ganglion. 



E. eye. 



F. fin. 

 Ft. foot. 

 Gi. gill. 

 Go. gonad. 

 H. heart. 



I.G. Visceral, ganglion. 



I.S. ink sac. 



L.V. lateral siphonal valve. 



M. mantle. 



M. C. mantle chamber. 



Me. mesenteron. 



Mo. mouth. 



Ne. nephridium. 



0. statocyst. 



P.G. pedal ganglion. 



Ph. pharynx. 



Ph. pen. 



Sa. salivary gland. 



Sh. Shell. 



Si. siphon. 



Si.f. siphonal folds. 



Si. V. median siphonal valve. 



S.S. shell sac. 



St. stomach. 



V.g. visceral ganglion. 



S.V. valve of siphon. 



TEXT FIGURE 5. Nuchal cartilage. 

 1. lateral point. 



d. dorsal point. 



1. articular surface. 



2. groove for the insertion of the siphonal valve. 



3. edge for insertion of nuchal retractor. 



4. origin of cephalic retractor. 



ventral point. 



9. median angle of collar (pen point). 



TEXT FIGURE 7. Diagram of the muscles of the fin. 



muscles which pass over the dorsal point of the mantle. 



dorsal angle of fin. 



muscles connecting the fins. 



lateral angle of fin. 



ventral angle of fin. 



longitudinal muscles. 



fin cartilage. 



