L 



inhabiting the United States. 487 



V 



foreign shell j the uniformity of the color, ours being 

 yellow, with an olivaceous tint and destitute of bands, 

 while that is remarkable for its great diversity of coloring, 

 and brilliant zones ; the greater prominence of the spire ; 

 the difference of the color of the animal, which Drapar- 

 naud describes as " commonly pale or a little greyish, or 

 slightly reddish'^ a description that could not be applied. 

 to the species In question; and lastly, •the eplphragm^ 

 which is a thin, transparent, membranous pellicle, as in 

 our other species, in place of an opaque, papyraqeous 

 one, as stated by that author. 



In the young shell the umbilicus, which is hardly large 

 enough to admit the point of a pin, Is open, and the lip 

 is simple. In a single specimen I have noticed some in- 

 distinct bands and lines. 



Having kept a large number of this species in confine- 

 nient, I have frequently had an opportunity of noticing 

 the manner in which the epiphragm Is formed, w^hich 

 does not appear to me to have been heretofore correctly 

 described- The collar of the animal having been brought 

 to a level with the aperture of the shell, a quantity of 

 gelatinous matter is thrown out, which covers it. The 

 pulmonary orifice Is then opened, and a portion of the air 

 within, suddenly ejected, with such force as to separate 

 the viscid matter from the collar and to project it, like a 

 bubble of air, from the aperture. The animal then quickly 

 withdraws further Into the shell, and the presence of exter- 

 nal air presses back the vesicle to a level with the aper- 



!als and forms the epiphragm. In some 

 of the European species in which the gelatinous secretion 

 contains more carbonate of lime than ours, the congelation 

 seems to take place at the moment when the air is expel- 

 led, and the epiphragm In these, b strongly convex. 





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