234 Lamarck's Genera of Shells. 



7th Family. 

 a LiMACiANA. (5 Genera.) 



i Branchiae resembling a vascular net-work, extended over the 

 side of an appropriate cavity, the aperture of which the animal 

 contracts or dilates at pleasure. They breathe only free air. 



This family is very remarkable, the individuals which com- 

 pose it being the only gasteropoda that breathe nothing but free 

 air, although their respiratory organ is truly branchial. Hence, 

 Lamarck proposes to call them pneumobranchial. They are 

 quite, or very nearly, naked. Their body is long, creeping on 

 an attached ventral disk, and bordered at the sides by an, often 

 very short, mantle. They live in the neighbourhood of water, 

 or in cool, damp places. 



1. Onchidium. 



This genus has no shell. 



2. Paumacella. 



Body creeping, oblong, inflated near the middle, where the 

 scutellum is situated, terminated by a tail, compressed at the 

 sides, acute above. Scutcheon oval, fleshy, adhering to the 

 posterior part, anteriorly free, containing a shell, and notched in 

 the middle of iis right border. Orifice for respiration, and 

 anus under the issure in the scutcheon. Four tentacula ; the 

 two posterior the largest. Orifice for generation between the 

 two tentacula, oi the right side. 



The Parmacelk is a land animal, nearly allied to the Umax, 

 but distinguished from it by the anterior half of its scutcheon 

 not being attache! to the body. In each genus the scutcheon 

 envelopes a solid, cretaceous body, Avhich, in the parmacella, 

 has the true form of a shell, whilst, in the limax, it is the mere 

 element of one. 



Type. Parmacella caliculata *. 



* Cup-shaped.~" Shell small, like a very flat bowl of a spoon, with a very 

 short papilliforni spire, contracted at its base, the aperture of its spire very 

 small, but the outer ip very much spread out, and rather irregular"— 

 " covered on the outsxle vi ith a light-brown, thin, horny epidermis." The 

 specific name and desaiption of the Parmacella, which we have given as 

 our type, is taken fron Mr. G. B. Sowerby. {Genera of Recent and Fossil 

 Shells.) The shell, fron which our figure is taken, was furnished us by the 

 kindness of Mr. Henry itut(^hbury. Lamarck gives but one species, P. OU- 



