Lamarck's Genera of Shells. 2^1 



2. Clio. 

 This genus has no shell. 



3. Cleodora. 



Body oblong, gelatinous, contractile, bi-alate ; the head on 

 the anterior part of the body, the posterior covered with a shell. 

 Head projecting, very distinct, rounded, with two eyes, and a 

 small subrostrated mouth. No tentacula. Two opposite mem- 

 branous, transparent, corda^^^e alee *, inserted at the base of the 

 neck. 



Shell straight, gelatino-cartilaginous, transparent, in the form 

 of a reversed pyramid, lanceolate, truncated and open at the 

 top. 



These animals, like the rest of the Pteropoda, float at ran- 

 dom, in the sea. 



Type. Cleodora jjyramidata-f. (Clio pyramidata. Lmw.) 



Shell triangular, pyramidal, short; month obliquely trun- 

 cated. American Ocean. 2 species. PI. VII, Fig. 108. 



4. Limacina J. 



Body soft, oblong, anteriorly very similar, in regard to the 

 head and alae, to the clio ; but spirally contorted, at the hinder 

 part, and enclosed in a shell. 



Shell thin, brittle, papyraceous, spiral; turns of the spire 

 united in a discoidal order, like the planorbis. 



The limacina is ill named, for it rather resembles a helix 

 than a Umax ; but the shell being flattened on the upper part, 



substance of tlie shell bears to that of the Hyalaea, until an opportunity 

 may occur of obtaining more accurate iiifonnation respecting this interest- 

 ing species. It may be described as follows. 



Shell transparent, very thin and fragile, hyaline, corneous, hastiform, 

 ai)ex recurved; open at both ends; superior aperture dilated, sharp 

 edged ; inferior round, very minute ; sides acute ; superior disk undulated ; 

 inferior rounded ; numerous transverse grooves on both side*. P. VII. 

 Fig. 107. The figure given (Plate vii. No. 8.) in Mr. Parkinson's Intro- 

 ductiun to the Study of Fossil Organic Kemaivi, as a Hyaltea, very much 

 resembles the other species of this genus, alluded to above. 



* Wings. Two membranes, situated as described in the text, which, 

 when extended, serve as sails, whilst the animal is iiuating on the surface 

 of the water. 



t Pyramidal. % From Umax, a snuil. 



