ACICULA. 39 



abundance of very clear aqueous mucus. It often 

 leaves half the foot exposed when all the other 

 parts are withdrawn. 



1. ACICULA. 



Shell subcylindrical, with a blunt tip; mouth ovate, 

 simple, outer lip simple, thin, slightly reflexed 

 over the pillar, forming a slight perforation. Ani- 

 mal with two long contractile slender F'9- ^ o. 

 tentacles, between which and the Vf 

 eyes, at their hinder base, are two 

 jagged blackish spots (fig. 10.). 



Dr. Turton (^Manual, ed. 1. p. 83.) appears to 

 have considered the spot at the base of the tentacles 

 as the rudiment of a lower pair. Dr. Hartmann 

 (^Sturm, Fauna, t. 1. f. 4.) describes the tentacles as 

 retractile ; but he uses the same term to describe 

 the tentacles of Cyclostoma and Carychium, which 

 agree with these in only being contractile, and not 

 retractile like those of Helices, and other land Mol- 

 lusca. 



This genus, on account of the similarity of its 

 shell, has been confounded also with Truncatella of 

 Risso, which is a marine animal, provided with gills 

 and a distinct operculum. 



The animal walks with its shell nearly perpen- 

 dicular, twisting it round in a very odd manner, and 

 then letting it suddenly fall again. 



9. 1. AcicULA/M5ca. Brown Acme. — Shell cylin- 

 drical, obtuse, glossy brown, transparent, with 



D 4 



