88 



BRITISH MOLLUSKS. 



and nearly five isothermally. The chief habitats of the genus are 

 the Central American, Chilian, and Bolivian provinces in the new- 

 world, and the Malayan in the old. Another feature in the distri- 

 bution of the Bulimi which adds to their generic importance is that 

 whilst the proportion in number of Helices in the two hemispheres 

 is nearly three to one, of Bulimi it is as two to three. The denser 

 and more widely spread forest vegetation of South and Central 

 America appears to be more favourable to the production and habits 

 of Bulimus than of Helix ; in the rainy districts of Venezuela the 

 shell is of quite a solid growth, with a richly variegated epidermis. 

 In Britain we have only three small ground species ; one, B. acutus, 

 inhabiting chiefly the south and western chalk downs near the sea; 

 a second, B. montanns, local in comparatively few places in the south 

 and midland counties ; and a third, B. obscurus, of smaller size, 

 which is very general throughout. 



1. acutus. Shell conically turreted, of eight to ten whorls, bight 



horny or brown, marbled with opake-white streaks, black- 

 banded below. 



2. montanus. Shell conically cylindrical, of seven whorls, oHve 



horny, minutely shagreened. 



3. obscurus. Shell smaller, turriculate cylindrical, fuscous 



horny, glossy. 



1, Bulimus acutus. Sharp Bulimus. 



SheU ; conically turreted, minutely umbilicated, thin, light horny, 



or brown, marbled with opake cream-co- 

 loured streaks and blotches, last whorl 



mostly encircled round the lower part by a 



fuscous black band ; whorls eight to nine, 



striated in a wrinkled manner, finely pli- 



cately crenulated at the sutures ; aperture 



ovate, lip simple, broadly reflected over 



the umbilicus. 

 Helix acuta, Miiller (1774), Verm. Hist, part ii. p. 100 



(not of Lamarck). 

 Turbo fasciatus, Pennant {V711),Brit. Zool. ed. iv. 



toI. iv. p. 131. pi. lxxxii. f. 119. 

 Helix cretaeea, Chemnitz (1786), Conch. Cab. vol. ix. part 2. p. 190. pi. 



exxxvi. f. 1263. 



