106 MTTRID^. 



Family MITRIDJE. 



The animal has a small, narrow head ; tentacles close together 

 at the base; eyes near the base or towards the outer middle of 

 the tentacles ; proboscis cylindrical, flexible, very extensible, 

 mantle enclosed ; siphon simple at the base ; foot small, 

 triangular, usually truncate in front. 



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. 



Mitra is related on the one hand with Valuta, 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 large size and 

 particularly by wanting the thick marginal varix of the lip. 



The dentition of the Mitridse presents several distinct types ; 

 so that Troschel and Gill have divided the family upon this 

 character. The group Cylindra has the teeth of Marginella 

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

 shell also recalls Marginellidse, and although the preponderance 

 of characters accords with Mitra, it may be reasonably considered 

 a connecting link with Marginella. Volutomitra has been 

 placed in Yolutidse on account'of the dentition of V. Grcenlandica, 

 the only Arctic species of Mitra, but I have preferred to retain 

 it and its congeners in Mitridse, because we know nothing of the 

 dentition of the numerous tropical species. Turricula and 

 Strigatella are allied by their dentition to the Olividse, and 

 Imbricaria to the Turbinellidse. 



Mitra has been divided by H. and A. Adams and others into 

 a number of subgenera, whilst Sowerby separates the species 

 into thirteen numbered but unnamed sections. The groups are 

 certainly not entitled to subgeneric rank, yet I believe that the 

 retention of Adams' names for the sections is better than to 



