224 Lamarck's Genera of Shells. 



3. Chiton *. 



Body creeping, oval oblong, convex, rounded at the extremi- 

 ties, bordered all round by a coriaceous skin, and partly 

 covered by a longitudinal series of testaceous, imbricated, 

 transverse, moveable pieces, connected with the borders of the 

 mantle. Head anterior, sessile ; mouth situated at the lower 

 part, covered by a membrane, and furnished with numerous 

 teeth, some simple, some with three points, and disposed in 

 several longitudinal rows. No tentacula nor eyes. Branchiae 

 disposed in series round the whole body under the border of 

 the skin ; anus below the posterior extremity. 



The shell of the Chiton is generally composed of eight 

 valves, sometimes of seven, or only six ; the middle valves are 

 rather larger than those at the extremities. They live in the 

 sea at moderate depths, and near the shore ; attaching them- 

 selves, but not permanently, to rocks and stones. 



Type. Chiton squumosus t. (Idem. Li7in.) 



Shell with eight valves, semlstriated ; body covered with 

 Small scales. 



Mediterranean, and American Seas. Six Species. PI. VII. 



Fig. 111. 



4. Patella:. 



Body entirely covered by an univalve shell ; two pointed 

 tentacula on the head, with eyes at their exterior base. 

 Branchias disposed in series all round the body, under the 

 border of the mantle ; anus and orifice for generation at the 

 right anterior side. 



Shell univalve, not spiral, enveloping, clypeiforlii, or flat- 

 tened conical, concave and simple below ; no fissure in the 

 margin ; summit entire, inclining to the anterior side. 



The summit is often the thickest part of the shell, and the 

 muscular attachment is very perceptible, on the concave side, 

 in many of the species ; and shews that the head of the animal 

 is always placed on the side towards which the summit inclined. 



t x'^av, a coat of mail. 



+ Scaly. Lamarck's second Species. His tjpe is C, gigas. 



X A umall deep dis 



