IT 2 MARGINELLID^. 



Distinguished by its Conus-like form, the columella with less 

 numerous plaits than in most of the species of Cylindra ; some 

 species, like Cylindra dactylus, however, appear to connect these 

 two forms. 



Family MARGINELLID^. 



Shell porcellanous, polished, usually smooth or with longitu- 

 dinal ribs ; spire short or immersed, body-whorl ample, aper- 

 ture nearly the length of the shell, the outer lip with usually 

 thickened margin, smooth or dentated within, the inner lip with 

 several distinct plaits on the columella. 



Animal with tentacles close together at the base, the eyes above 

 the base or near the middle of the tentacles, mantle with expanded 

 side-lobes covering the back of the shell as in Cypraea ; siphon 

 elongate, foot large, truncate in front, produced behind. Oper- 

 culum none. 



Dentition (x, 6). In possessing rhachidian pieces without 

 laterals, the lingual armature of Marginella resembles that of 

 Yoluta, whilst the shape of the plate and its dentated edge are 

 very similar to that of Mitridse — lateral teeth being added in the 

 latter famil3% A single species of Erato (the only one examined) 

 possesses three lateral teeth on each side like the Cyprseidse, and 

 on this ground some systematists place Erato in that familj^ 

 Marginella glabella sometimes possesses an operculum, but 

 generally does not have it ; some of these operculate specimens 

 also have a single lateral tooth on each side of the rhachidians 

 on the lingual ribbon. Pseudomarginella, Carriere, is founded 

 upon specimens possessing this very different dentition ; the shell 

 does not differ at all from specimens of M. glabella in which the 

 dentition is normal. 



The shell being covered by the mantle-lobes receives a polished 

 surface and is devoid of epidermis, thus resembling externally the 

 Cowries and Olives, whilst the plaits on the columella connect 

 the family with Mitridse. 



Erato, Risso. 



Bistr. — IT sp. Europe, West Indies, So. Africa, Indian 

 Ocean, Philippines, Polynesia, Tropical W. America. Fossil. 

 Eocene — ; Europe. So. Australia, N. America. E. laevis, Donov. 

 (lv,54). 



Shell obovate, polished ; spire short, conical, distinct ; aper- 

 ture linear ; outer lip without varix, but thickened towards the 

 middle, and denticulated within ; columella with distinct plaits 

 at the fore-part. 



ERATOPSis, Hoernes and Auinger. Shell granular-tuberculate, 

 with a longitudinal sulcus on the back of the body-whorl, as in 

 Trivia. Includes five living species, and several forms from the 

 Austrian tertiary. E. Schmeltziana, Crosse (Iv, 55). 



