SCALARIA. 143 



witli an especial reference to individuals. Beautiful is 

 the variety which they present, — 'the more remarkable 

 because the moUusk does not wait till his faculties become 

 developed ; he commences the formation of his rings at a 

 very early period. It seems, also, as if each distinct species 

 had its own peculiar pattern, transmitted from one genera- 

 tion to another, — a kind of heraldic crest or emblem dis- 

 tinctive of the tribe. In the well-known Scalaria pretiosa 

 of the Chinese Sea, the rings, or varices, are situated at 

 moderate intervals, increasing in area in exact geometrical 

 proportion with the size of the shell ; in 8. imjjerialis they 

 are developed at more frequent intervals ; in the S. lyra 

 they resemble silken threads ; in S. raricosta they are re- 

 motely and irregularly deposited ; and in S. alata they are 

 characterized at the upper part by the addition of a wing- 

 like process. But the most curious development is in 

 the S, magnifica, in which the whorls are contiguous, and 

 the typical peculiarities of the genus seem scarcely to 

 enter into its plan of growth, a few slight rings being 

 alone discoverable, at irregular intervals, on the two last 

 whorls. 



This genus principally affects the West Indies, Pacific 

 Islands, California, and New Holland. 



