168 MITRIDuJ). 



this character. The group Cjdindra has the teeth of Marginella 

 and is placed near that genus by these authors ; the form of the 

 shell also recalls Marginellidae, and although the preponderance 

 of characters accords with Mitra, it may be reasonably con- 

 sidered a connecting link with Marginella. Volutomitra has 

 been placed in Volutidae on account of the dentition of V. 

 Grcenlandica, the only Arctic species of Mitra, but I have pre- 

 ferred to I'etain it and its congeners in Mitridse, because we 

 know nothing of the dentition of numerous tropical species 

 referred to it. Turricula and Strigatella are allied by their 

 dentition to the Olividse, and Imbricaria to the Turbinellidas. 



Some of the larger species have no operculum, but it is often 

 present, though small and rudimentary, on the foot of the smaller 

 species. 



Shell with acute apex, usually well developed spire and 

 plicate columella ; for the most part destitute of epidermis, 

 which is very thin, smooth and translucent when present. 



Miti'a is related on the one hand with Yoluta, on the other 

 with Marginella ; it is distinguished from the former by its 

 columellar plaits, of which the largest are posterior whilst in 

 Voluta they are anterior, by its form, and the apex, which is 

 never papillary ; from Marginella it is distinguished by its much 

 longer spire, less polished surface, generally larger size and par- 

 ticularly by wanting the thick marginal varix of the lip. 



Mitra, Lamarck. 



Syn. — Thiarella, Swains. Mitraria, Raf. Mitrolites, Krag. 

 Isara and Ziba, H. and A. Ad. 



Diatr. — Over 200 sp. Tropical and subtropical, but a few 

 small species being found in the colder latitudes. Bathymetri- 

 cally they range from low-water to eighty fathoms, the smaller 

 species being usually found along shore-lines. About a hundred 

 fossil species have been described, commencing with the creta- 

 ceous period. M. episcopalis, Lam. (Iv, b6). 



Shell fusiform, thick ; spire elevated ; aperture small, narrow, 

 notched in front ; cokimella transversely, somewhat obliquely 

 plicate ; outer lip thick, smooth within, not variced externally. 



The animal of Mitra has in general a very short foot, straight 

 and continuous from side to side in some species, but in others 

 notched and produced, with a thickened anterior margin. It is 

 commonly narrow and rounded, or acuminated posteriorly, and 

 it often bears a very small semitransparent horny opercuium, in 

 some instances scarcely visible. The siphon is mostly directed 

 forward, and the somewhat short, tapering tentacles have the 

 eyes either situated about half-way, or they are placed on the 

 outer side of the base. The head is long and ver}^ flat, and the 

 tentacles are very close together at their bases. The proboscis 



