BULLID^. 207 



collection of molliisca could scarcely be thrown together, if 

 picked out from various parts of the system for the purpose. 

 There are the A]ilustrum and Htjdatina with banded out- 

 side bubble-shells, crawling on their leaf-like discs, and exhi- 

 biting no fewer than six ornamental projections on the sides 

 of their heads; while the Tornatina, with his little rolled 

 cylinder of a shell and narrow foot, is content with two. 

 The Akera, whose shell is represented by an elastic roll of 

 transparent horn, has a long head, unornamented ; and the 

 Scaphander wraps up his head and body in a leather-like 

 lobe, so as to present no appearance of life under his solid, 

 wood-coloured, pear-shaped test. Some of the species look 

 like rolled-up slugs, and others like tadpoles; and while 

 miline covers its shell and body with what resembles four 

 small mats, the LoUger appears all life and animation with 

 four wings. 



" Shell none, external or internal," is all that Mr. Arthur 

 Adams can say as to that part of their character, when, in 

 his monograph, he endeavours to throw together the peculi- 

 arities of this dissimilar group. 



Still the affinities of these mollusca with each other are 

 traceable through every divergence. The head in every 

 genus is more or less lobed; the gills are placed on the right 



