96 BRITISH MOLLUSKS. 



The shell of Azeca tridens is of a peculiar chrysalis form, trans- 

 parent and shining, looking very much as if it were membranaceous 

 and flexible during the life of the animal. The aperture is small, 

 sloping and attenuated towards the base, ear-shaped, and a little dis- 

 torted. Within are three prominent teeth, with sometimes one or two 

 smaller teeth, including a small threadlike plait winding into the 

 interior. 



It is only sparingly diffused in England, between the northern 

 and south-western counties, and has not been observed in Scotland 

 or Ireland. France and Germany appear to be the only habitats 

 recorded on the Continent. 



Achatina acicula. (Considerably enlarged.) 



Genus VIII. ACHATINA, Lamarck. 



Animal ; body slender, attenuated to a point behind, white, carry- 

 ing a narrowly convoluted colourless hyaline shell, upper pair 

 of tentacles slender, lower pair very short, eyeless. 

 Shell ; imperforate, elongated, narrow, hyaline, colourless, whorls 

 smooth, margined at the sutures ; aperture small, columella 

 involute, truncated at the end. 

 The brilliant tropical genus Achatina, including the largest of all 

 land mollusks, is represented at its northernmost Hmit, in Britain, 

 by a single small species, which, with comparatively few exceptions, 

 is the smallest of all. In the sultry woods of West Africa, 

 Achatina produces a shell as large as an ostrich's egg. The shell of 

 our solitary British species scarcely measures the fifth of an inch 

 in length. It belongs, however, rather to the Glandina section ot 

 the genus, inhabiting chiefly Central America and the West Indies, 

 but well represented, though more sparingly, in Southern Europe 

 and Algeria, Madeira, Ceylon, and Hindostan. The nearest allied 



