184. 



SHELLS AND SHELL-FISH. 



PART 1. 



Analogies of the Genera Clausilia and Pupa. 



Sub-genera of 

 Pupa. 



Sipho7iostoma. 

 Megaspira. 



Gonospira. 



Analogies. 



f Spire exceedingly long, the upper > 

 \ portion deciduous. J 



f Spire greatly lengthened, the up- 7 

 / per portion persistent. J 



Spire moderate, with few whorls, 'J 

 the tip thick and obtuse; thef 

 aperture generally without f 

 teeth. 3 



"Spire moderate, but with manyT 



Sub-genera of 

 Clausilia. 



Clausilia. 



Balia.* 



rbpire moiierate, out witn manyT 

 Pupa. -^ wliorls of nearly equal thick. > Pupella. 



L ness 3 



PUcadotnus. 



r Whorls few ; the outer lip dilated 7 

 t and broadly margined. J 



Macrodontes. 



(170.) Our next genus is Helicina, — a group of 

 remarkable shells^ of which, as near forty species are now 

 known, the sub-genera may be advantageously charac- 

 terised. This will be done in our systematic arrange- 

 ment, and in the mean time a few general remarks is all 

 that we can here insert. Tfiey are small helix-formed 

 shells, distinguished by their semilunate aperture, which 

 is closed by an operculum. We have not seen, as yet_, 

 any intermediate form which renders the passage between 

 them and the last genus sufficiently clear. The animal, 

 as seen in H.occidentalis (fig. 28.), has been well drawn 

 by Guilding; it has only two tentacula, with the eyes 



at the base. In this respect the Helicince, as Cuvier 

 observes, have a close affinity with the Cyclostomes, 

 many of which are also turbinated shells, and all are 



* I should conceive, theoretically and analogically, that Bal/a would 

 represent Gonospira by its toothless aperture ; and that the prototype of 

 Megaspira would be perfectly like Clausilia, but without any teeth or 

 folds, and the spire (probably) persistent. 



