53 HELIX. SNAIL-SHELL. 
36. Helix nitidissima. Linn. Trans, v. pi. 1» I- 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, 
with two volutions, and slightly perforated. 
Pembrokeshire coast: minute. 
These ten last species are very obscure and indistinct; 
some of them probably the young of other species. 
C. With the volutions rounded ; imperforate at the bate, 
3S to 42. 
38. Helix ianthina. Blue Snail-shell. Fig ^ • 
Lister, pi. 5/2. f. 24. 
Shell somewhat orbicular, obtuse, thin, brittle, trampa* 
rent, of a whitish color more or less tinged with violet blue 
or pale purple: spires four, a little rounded and wdldc- 
fined by the line of separation, slightly striate longitudinally 
in an oblique direction; the first very large, slightly cari¬ 
nate at the base which is of a deeper violet color, ad 
striate both circularly and longitudinally y inside pple vio¬ 
let: aperture dilated; the outer-lip very thin; pillar-lip 
extending in a straight direction beyond the body frqm the 
base, so a 3 to give the aperture a somewhat triangular ap¬ 
pearance on that side, and a little curled back so as to fora 
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. <c 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 violacea; they are about the size of a snail, ad 
are supported upon the surface of the water by a small chis- i 
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 seenj 
also as a nidus for the eggs. It is probable thatitnerer 
