60 MOLLUSC A. GASTEROPODA 



united to the body in almost its whole length. Those which have the body poste- 

 riorly in a spiral form, covered by a spiral shell, and the foot separate, form the pre- 

 ceding order, Trachelipoda. 



Lamarck divides the Gasteropoda into two sections and seven families, as follows : 

 SECTION I PNEUMOBHANCHI^: Branchiae in the form of a vascular net on 



the wall of a particular cavity, opening by a hole which the animal contracts and 



dilates at pleasure. They respire air. Limacinea. 



SECTION II. HYDROBRANCHUE. Branchiae in filaments or laminae, pectinated 

 or tufted. They respire in water. 



a. Branchiae placed in a particular cavity towards the posterior part of the back, and 

 covered either by the mantle or by an opercolar shield. 



* With tentacula. Laptysiacea. 

 * Without tentacula. Bullacea. 



b. Branchiae placed in a particular cavity on the back, situated anteriorly near the 

 neck. Calyptracea. 



c. Branchiffi exterior, placed under the margin of the mantle, and disposed in a 

 longitudinal series, either around the body or on one side only, and not in a par- 

 ticular cavity. SemiphyUidiacea, Phyllidiacea. 



d. Branchiae exterior, placed above the mantle, either on the back or sides, and not 

 in a particular cavity. Tritoniacea. 



SECTION I. PNEUMOBRANCHLE. 

 FAMILY I LIMACINEA. 



Branchiae in the form of a vascular net on the wall of a par- 

 ticular cavity, the opening of which the animal can dilate or 

 contract at will. 



The animals of this family are almost or entirely naked. Their body is elongated, 

 and they crawl by means of a ventral disk bordered on the sides by a very narrow 

 mantle. 



Gen. 1. VITEINA, Lam. 



Body elongated, straight, separated from the foot posteriorly, 

 and enveloped in a shell ; four tentacula, the two anterior 

 very short ; shell small, very thin, depressed, with a very short 

 spire, and body whorl very large ; aperture large, rounded, 

 oval, the left margin slightly bent inwards. 



V. pelhtcida, Drap. Inhabits Europe near the margin of ponds and 

 moist places Lam. vi. 2. 53. 



Gen. 2. TESTACELLA, Lam. 



Body oblong, with a shell on the posterior extremity ; four ten- 

 tacula, the two largest bearing the eyes ; orifice of the anus 

 and for respiration at the posterior extremity ; shell very 

 small, external, almost auriform, slightly spiral at its summit ; 

 aperture very large, oval, with the left margin inflected inwards. 



T. haliotidea, Lam. Body projecting on the back, with the shell 

 small. Inhabits Southern Europe, under stones and in the ground. 

 Lam. vi. 2. 52. 



Gen. 3. LIMAX, Lam. Lin. 

 Body oblong, naked, convex above, furnished anteriorly with a 



