VII 



MOLL USGA —MUSCULATURE 



127 



mention the nuclial cartilage and the cartilages for looking the cleft of the mantle 

 cavity (p. 55). In the diaphragm, i.e. in the posterior wall of the visceral dome, 

 over which the inantle depends, there is in the Decapoda a cartilage near the 

 funnel, the diaphragm cartilage. Finally must be mentioned a dorsal cartilage, 

 which is specially strongly developed in Sepia. It lies, posteriorly, on the anterior 

 border of the mantle, where the latter pro- 

 jects over the neclc ; it bears the same 

 relation to the nuchal cartilage as does 

 the cartilaginous projection on each side of 

 the mantle to the cup-shaped socket at each 

 side of the base of the funnel or siphon (c/. 

 Fig. 80). 



In Sepia the dorsal cartilage is continued 

 in the shape of a cartilaginous rod running 

 up on each edge of the shell. The inner 



edges of these rods have a groove into which 



the edge of the shell fits, and thus form a 



kind of fold round its lateral edges. 



In the Odopoda there is a cartilaginous 



band on each side in the dorsal integument 



wlrich may correspond with the dorsal carti- 

 laginous rods in Sepia. It is possible that 



the "internal shell" of the only Octopod 



in which a shell is found, viz. Cirrho- 



teittkis, is not in reality homologous with 



the shell of the Decapoda, hut corresponds 



with the cartilaginous bauds of Octcypus 



fused in the middle line. 



The (basipterygial) cartilages, univers- 

 ally found at the bases of the fins in the 



Decapoda, complete the list. 



With regard to the musculature 

 of the Dibranohia, that of the mantle, 

 the fins, and the arms cannot be 

 described in detail. We note, how- 

 ever, that the pallial musculature 



Pig. 110.— Diagram of the more important 

 parts of the Dibranchiate musculature. 

 Body seen from the left side, v, Ventral ; cI, 

 dorsal ; a, anterior ; p, posterior ; 1, depressor 

 infundibuli; 2, retractor capitis lateralis; 3, 

 retractor capitis medianus; 4, niusculus col- 

 is principally attached to the shell laris; 5, adductor infundibuli; e, shell; 7, 

 or to the dorsal cartilage, the fin- dorsal cartilage; 8, nuchal cartilage; 9, cephalic 



cartilage ; 10, mantle cavity ; 11, cartilaginous 



musculature to the fin-cartilages, and 



socliet of the locking apparatus on the posterior 

 wall of the visceral dome ; 12, corresponding 

 cartilaginous Itnob on tlie inner wall of the 

 mantle, which fits into 11 ; 13, funnel or siphon 

 (infundibulum) ; 14, diaphragm cartilage. 



the brachial musculature to the an- 

 terior side of the cephalic cartilage, 

 and partly to the basi-brachial carti- 

 lage when such is present. 



The remaining musculature can be best explained with the assist- 

 ance of the accompanying diagram (Fig. 110), which represents the 

 musculature of Enoploteuthis. 



The strong paired depressor infundibuli (1) rises from the shell 

 on each side (or from the dorsal cartilage), and runs downwards and 

 backwards to the base of the funnel and to the cartilaginous socket. 

 From it spring most of the muscles of the anterior wall of the funnel. 



