240 



SHELLS AND SHELL-FISH. 



the shells of these latter really are, we know not ; hut we 

 have two, very thin and hardly opaque, which, judging 

 from his figures, we suspect are of Quoy's Cryptostoma : 

 they are as brittle as those of Vitrina, but are of that 

 semitransparent whiteness which shows they must be 

 internal shells, and they have no sculpture whatever. 

 As to the Sigaretus cancellatus of Lamarck, it is mani- 

 fest nothing can be advanced beyond mere conjecture 

 until the animal is known. Of all these, therefore, the 

 NaticincE and the NeritincB are the only sub-families 

 which can safely be relied upon as unquestionable ; yet 

 even their genera cannot be demonstrated with that pre- 

 cision that could be wished. 



(^21.) The intimate connection between this family 

 and the Turbidce is too evident to require any demon- 

 stration. Thus, then, do we return to the latter group, 

 and the great circle of the phytophagous Gasteropoda is 

 rendered complete. On looking to its component parts 

 or families, and to those of the zoophagous or carnivo- 

 rous tribe, we find them representing each other in this 

 manner : — 



Analogies of the Phytophagous and Carnivorous 

 Gasteropoda. 



Families of the 

 Phytophaga. 



HeLICIDjE. 



TaocHiD^. 

 HaliotidjE. 



Naticid^. 



TURBIDID^. 



Analogies. 



Typical of their respective tribes. 



Sub-typical. 



"Tentacula very short, sessile;'^ 

 ) shell with the body-whorl ex- f 

 ) cessively large; the spire very f 

 , short, and scarcely raised. j 



'Animal, when crawling, larger'^ 

 I than its shell, which is smooth, ( 

 I and generally polished; spiref 

 nearly or quite obsolete. j 



Animal with a proboscis-formed'^ 

 ] mouth, and a respiratory si- ( 

 I phon; eyes placed on the sides i 

 . of the tentacula. j 



Families of the 

 Zoophaga. 



MURICID^. 

 TURB£NELLID^. 



VOLUTID^. 



CvPRiEID*. 



SxROMBIDiE. 



There is every reason to suppose, from the three last 

 analogies, that the two first Avill rest also upon the struc- 

 ture of the animals, and not upon their shells ; but it un- 

 luckily happens we are totally ignorant of that inhabiting 



