STENOGYRA. 193 



It is very voracious in its habits. I kept a number of individuals received from 

 Charleston a long time as scavengers, to clean the shells of other snails. As 

 soon as a living Helix was placed in the box with them, one would attack it, 

 introduce itself into the inner whorls, and completely remove the animal. 

 Leaving a number of Succinea ovalis, Old., with them one day, the former dis- 

 appeared entirely in a short time. The Stenogyra had eaten shell as well as 

 animal. 1 



The young shell is thin, transparent, and fragile; the old is opaque and 

 rather thick. It is very peculiar in respect to the manner of breaking off and 

 abandoning successive portions of the spire. According to the plan upon which 

 the shell is projected, it would, when it reaches the full size which it attains in 

 this country, possess ten or more full volutions, if it retained all of them from 

 the apex downward. But as fast as the growth of the animal compels it to in- 

 crease the number and volume of the whorls, it releases its connection with the 

 superior whorls, creates a new attachment lower down, forms a new apex or 

 spiral calcareous septum, which separates it from the abandoned part, and, in 

 some manner which is not understood, breaks and throws off those whorls 

 which are no longer of use. 2 This commences at a very early period ; the 

 original apex being thrown off when the shell has acquired 5 or 6 whorls. 

 They differ in this particular from most of land shells, and especially from the 

 Helices, which always, so far as I know, retain their original attachment to the 

 apex of the shell. It has been thought that the breaking of the spire, after 

 being left by the animal, and becoming dry and brittle, is accidental ; but I 

 conceive that the effect is much too constant to be accounted for in that way. 

 I have never been able to find a mature specimen with the apex. And in all 

 the various countries which it inhabits, including the whole southern part of 

 Europe, the northern part of Africa, the islands of the Mediterranean, the Ca- 

 naries, Madeira, etc., the same peculiarity attends it. If it were only an acci- 

 dent, some few in this wide extent might escape. I doubt not, therefore, that 

 it is effected by the action of the animal itself. It may be that the calcareous 

 matter of the shell is absorbed at the point of division, previous to the forma- 

 tion of the new septum. 



Mr. Say made out his description from an immature specimen. 



The cpiphragm is white, pearly, and opaque ; it fills up the aperture, and 

 when pushed out by the animal, generally falls entire. It may be seen in num- 

 bers about their winter-quarters. Its outline is represented in Vol. III. PI. 1. 



Jaw and lingual membrane : see p. 191. 



Lingual membrane (PI. IV. Fig. Q, b is one of the first marginals, c extreme 



1 I find no notice of any such carnivorous habits mentioned by Moquin-Tandon. It 

 may be the species prefers vegetable food, but being deprived of that was forced by hunger 

 to devour animal food. 



Moquin-Tandon says (on the authority of Gassies) that the animal breaks ofl" the 

 upper whorls by jerking round its shell against some hard object. 

 VOL. IV. 13 



