UNIVALVE MOLLUSCA. 465 
species of Pterocera are found in the seas of both hemispheres, their 
vulgar denomination being sea-spider or scorpion shells. A glance at 
the illustrations (Fig. 309, Preroceras scorpio ; Fig. 310, P. millepeda ; 
Fig. 311, P. chiragra ; and Fig. 312, P. dambis) will satisfy the reader 
as to the general correctness of this designation. 
Fig. 311.—Pteroceras chiragra (Linnzus). Fig. 312.— Pteroceras lambis (Linnzus), 
The genus Pteroceras, whose remarkable form is so well calculated 
to excite our admiration, has yet another attraction: the colouring of 
the shells exhibits many shades, which are particularly varied towards 
the opening, where it is generally distinguished by great freshness 
and brilliancy, which, added to its other characters, render it among 
the most interesting of all the Gasteropods. 
