95 



though not very likely, when determined, to evoke, any change in the classi- 

 fication ; the alimentary system not being so much influenced by the diffe- 

 rence between digesting animal and vegetable matter, as is the respiratory 

 system by the difference of inhaling air and water. 



Sixteen genera may now be referred to this family, including one which I 

 have found it necessary to propose under the name of Fastigiella. 



Genus 1. TRITON, Be Montford. 



Vnimal ; disc oval, short, thick, carrying a smooth oblong oper- 

 culum, mostly fitting the aperture of the shell ; head stout and 

 rather prominent, somewhat square, with a pair of long slender 

 pointed tentacles, protruding from the front corners, having the 

 eye placed upon the outer side near the base ; at the under part 

 of the head is a small slit, through ivhich a proboscis is eccserted 

 for the capture of prey ; respiratory siphon varyiny in length 

 according to species. 



Shell ; oblong or rounded, with the canal sometimes very short, 

 sometimes long, and a little recurved, covered in some instances 

 with a strong bristly, hairy epidermis j whorls crossed with a 

 single solitary varix on each, but very irregularly, and it is 

 occasionally wanting ; Up thickened and crenulated, sometimes 

 channelled at the upper part. 



The genus Triton includes a considerable portion of that extensive and 

 much-admired series of CanaUfera, whose shells exhibit a peculiarity in 

 their mode of formation which is supposed to indicate periods of rest in the 

 calcifying functions of their animal inhabitant. It consists of the deposit 

 of a marginal ridge, with all its varieties of structural embellishment, at 

 intervals, as highly finished, and in as perfect condition, as Nature, in the 

 beauty and harmony of her operations, would lead us to anticipate only at 

 maturity. These varices of fronds, spines, laminae, or tubercles are secreted 

 by certain filamentary processes, which are exserted, it is assumed, along 

 the edge of the mantle, anterior to a season of rest ; that is, the animal has 



