168 MITRINiE. 



of the tentacles. Mantle enclosed, siphon simple at the 

 base. Foot small and triangular. 



Operculum none or rudimentary. 



Shell with the columella more or less plicate ; apex of 

 spire acute. 



Some of the larger species of Mitridce have no oper- 

 culum, but it is often present, though small, on the foot 

 of the smaller species. The Philippine Archipelago, and 

 other groups of islands, seem principally to harbour 

 these animals, few species being found on the shores 

 of continents. 



Sub-fam. MITRTN.^. 



Head moderate ; eyes usually near the outer middle or 

 tip of the tentacles ; foot truncate in front. Shell for the 

 most part destitute of epidermis; columella distinctly 

 plicate. 



Genus mitra, Lamarck. 



Shell fusiform, thick; spire elevated, acute at the 

 apex; aperture small, narrow, notched in front; colu- 

 mella obliquely plicate ; outer lip thickened, smooth in- 

 ternally. 



8yn. ThxdiXeWdi, Swains. Mitraria, i?a/?w. Mitrolites, 

 Krug. 



Ex. M. circulata, Kiener, pi. 19, fig. 1. Shell, M. 

 episcopalis, Lmticeus, fig. 1, a. 



When irritated, some species of Mitra emit a purple 

 fluid having a nauseous odour. They are chiefly deep- 

 water animals, living in from fifteen to eighty fathoms ; 

 the greater number are from the Philippines ; some, how- 



