172 POPULAR BRITISH CONCHOLOGY. 



sinistral direction; so that, when the full-grown pyramid is 

 formed, its apex consists of a twisted knob. 



YI. EuLiMELLA. — In all important characters the animals 

 of this genus resemble those of the two last, but the shells, 

 although, like them, formed with a sinistral spire, are like 

 those of the genus Eidima, pyramidal, with numerous whorls, 

 and brightly polished. Of the four British examples, 

 ^. Scillce is the most regularly pyramidal, with the sides 



straight, and the aperture angular ; 

 E. acicula, less regular and less angular; 

 E. affinis, with the whorls a little bulging ; 

 E. davulus, with the apex very obtuse. 



VII. Truncatella Montagtii. — This minute mollusc, 

 requiring a mixture of fresh-water with the briny element 

 in which he dwells, chooses those places accessible to the 

 purer streams; he has a produced muzzle and triangular 

 tentacles, with eyes at their base. When young the shell 

 is transparent and smooth; after three or four whorls it 

 swells suddenly, is slightly ribbed and puckered at the su- 

 tures ; and when adult, the thin tapering whorls fall oflP, 

 leaving a truncated, cylindrical figure of three or four turns 

 to the remainder. 



YIII. Otina otis has a very small, glossy brown, obliquely- 



