272 



HELICID^E. 



lip, it closely resembles a young or incomplete Clausilia, 

 and might lead to the supposition that its growth or deve- 

 lopment had been suddenly arrested. It wants, however, 

 the clausilium or twisted internal plate which is charac- 

 teristic of the adult Clausilia, as well as the oblique 

 teeth or folds which contract the aperture of that shell. 

 In the small tubercular tooth which is occasionally 

 formed on the pillar, Balia has some affinity to the 

 genus Vertigo ; but the mouth of the shell in the present 

 genus is of a different shape, and the spire is more elon- 

 gated or drawn out. The shell of Balia, when viewed 

 in a mirror (so as to make the spire appear dextral), is 

 not unlike that of a wide-mouthed Pupa. The soft parts 

 of the animal do not present any peculiarity, or appear 

 to be different from those of the other genera above men- 

 tioned. The members of this genus are inactive in their 

 habits, and are fond of shade and moisture, but not of 

 excessive wet. They are usually found in the crevices 

 of rocks and walls and under the bark of old trees ; and 

 they probably feed on the spores of mosses and other 

 Cryptogamous plants, as I have observed them after a 

 shower of rain apparently thus occupied, while slowly 

 crawling over the trunk of a sycamore. They may be 

 called the " Tree-snail." 



The present genus was first made known by Dr. Gray 

 in the ' Zoological Journal' (vol. i. p. 61) under the 

 name of Balea, from MS. information furnished by Mr. 

 Prideaux, an assiduous conchologist and friend of Dr. 

 Leach. In a posthumous work of the latter author, 

 entitled ' A Synopsis of the Mollusca of Great Britain,' 

 which was edited by Dr. Gray and published in 1852, the 

 same genus appears as Balcea. The word is probably 

 taken from balius (pro badius), and not, as M. Bour- 

 guignat supposed, from /3aAios (maculosus), as the shell is 



