MUSCULAR SYSTEM. 14J 



cles for the calcified jaws, is provided with broad muscular 

 feet, like the expanded feet of an argonaute, and supporting 

 numerous sheathed tentacula. In the argonaut a, (Fig. 68. A,) 

 there are eight muscular long feet provided with large sessile 

 suckers, as in other octopods. The ventral, or anterior sur- 

 face of the body is directed towards the concave or spiral 

 side of the shell, as in the planorbis, and other mollusca with 

 orbicular shells, and the dorsal part of the animal with the 

 expanded pair of membranous feet (^,) are placed next to 



FIG. 68. 



B 



the convex outer margin of the shell (a.) The mantle is 

 spotted externally, as in the naked cephalopods, and is des- 

 titute of muscular fins, as seen in Fig. 68. B, which repre- 

 sents the animal removed from the shell. The shell cover- 

 ing a part of the body has been observed by Poli in the 

 ovum, as represented in Fig. 68. C. a. The muscular por- 

 tion of the posterior pair of feet (Fig. 68. B. gj) and the 

 gradually diminishing sessile suckers are continued around 

 the margin of the expanded membranous part (Fig. 68. A. h,) 

 so that this pair of feet may be employed as organs of pre- 

 hension, or for creeping at the bottom, or for swimming 



L 2 



