Lamarck's Genera of Shells. &Si 



|)ressed, slightly truncated tentacula, with eyes at their internal 

 base. Foot short, elliptical, rather narrower than the body. 



Shell thin, obliquely conical ; summit pointed, inclined 

 backwards ; aperture oval ; margin very simple. 

 ., Type. Ancylus lacuitris* . (Patella lacustris. Linn.) 



Shell semiovate, membranaceous ; vertex subcentral ; aper- 

 ture suboblong-ovate. France. PI. VII. Fig. 121. 3 Species. 



i;th Family. 

 BuLLiEANA. (3 Genera.) 

 Branchije situated in a cavity, near the posterior part of the 

 back, and covered by the mantle. No tentacula, 

 1. Acera. 

 This genus has no shell. 



2. Bullsat. 

 Body elongated oval, slightly convex above, divided trans- 

 versely into an anterior and a posterior part. Lateral lobes 

 of the foot, with rather a thick border, and reflected upwards. 

 Head scarcely distinct. No tentacula. Branchiae dorsal, 

 situated under the posterior portion of the mantle. Shell con- 

 cealed in the mantle, above the branchia;, and not adhering to 

 the animal by any muscular attachment. 



Shell very thin, partially convolute, and spiral on one side ; 

 no columella, nor projecting spire; aperture very large, di- 

 lated at the upper part. 



One Species, Bullcea apertaX (Bulla aperta. Linn.) 



The last whorl of the volute, is terminated by the right 

 margin of the aperture. European Seas. PI. VII. Fig. 122. 

 3. Bulla V 

 Body oblong-oval, slightly convex, divided at the upper part 

 into two transverse portions ; mantle posteriorly plicate. Head 

 very indistinct. No apparent tentacula. Branchise dorsal, 

 posterior; covered by the mantle. Anus on the right side. 

 Posterior part of the body covered by an external shell, ad- 

 hering by a muscular attachment. Shell univalve, oval-glo- 

 bular, convolute ; no columella, nor projecting spire, or only 



.* Of the pools. t As nearly allied to the bulla.] 



^ Open. § A bubble. 



