58 HELIX. SNAIL-SHELL. 



36. Helix nitidissima. Linn. Trans, v. pi. 1. f. 22 to 24, 

 Shell horn-color, beautifully glossed, with two volutions, 



very finely striate transversely. 

 Pembrokeshire coast : minute. 



37. Helix bicolor. Linn. Trans, v. pi. 1 . f. 25 to 27- 

 Shell horn-color, opake, white within, quite smooth, 



two volutions, and slightly perforated. 

 Pembrokeshire coast : minute. 



These ten last species are very obscure and indistinct; 

 jsome of them probably the young of other species. 



C. With the volutions rounded ; imperf orate at the base* 

 38 to 42. 



38. Helix ianthina. Blue Snail-shell 

 Lister, pi. 572. f. 24. 



Shell somewhat orbicular, obtuse, thin, brittle, transpa- 

 rent, of a whitish color more or less tinged with violet blue 

 or pale purple : spires four, a little rounded and well de- 

 frned by the line of separation, slightly striate longitudinally 

 jn an oblique direction; the first very large, slightly cari- 

 nate at the base which is of a deeper violet color, and 

 striate both circularly and longitudinally ; inside pale vio- 

 let : aperture dilated; the outer-lip very thin; pillar-lip 

 extending in a straight direction beyond the body rrqm the 

 Ibase, so as to give the aperture a somewhat triangular ap- 

 pearance on that side> and a little curled back so as to form 

 an incipient perforation; breadth half an inch; height 

 about as much. 



The following observations, extracted from Cook's Voy- 

 ages, p. 14, will satisfactorily account for their occasional 

 appearance, wafted by waves and tides, and driven by 

 storms, on the British shores. " We also took several of 

 the shell-fishes, or testaceous animals, which are always 

 found floating Upon the water, particularly the Helix ian- 

 thina and yiolacea ; they are about the size of a snail, and 

 are supported upon the sut face of the water by a small clus- 

 ter of bubbles which are filled with air, and consist of a 

 tenacious slimy substance that will not easily part with its 

 contents : the animal is oviparous, and these bubbles seem 

 ^Iso as a nidus for the eggs. It is probable that it never 



goes 



