12 GASTEROPODA. 



aperture, with an expanded and flattened inner lip. They 

 commence in the Miocene Tertiary. Ringicula (fig. 391, c) 

 has a ventricose shell, with a small spire, the columella 

 callous and deeply plaited, and the outer lip thickened and 

 reflected. The genus commences in the Miocene Tertiary, 

 and is represented by living species. We may also, perhaps, 

 place in this family, possibly in the neighbourhood of Tcrehra, 

 the Silurian genus Suhulites (391, h), which in this case is 

 the most ancient representative of the family Buccinidce. 

 The shell in this genus is very long and slender, with a long 

 spire, and an extended body- whorl. The mouth is narrow, 

 with a sharp, not callous lip ; the columella is truncated 

 below, not plaited or toothed ; and there is a deep basal 

 notch. The Helmet-shells (Cassis) begin in the Eocene, and 

 are distinguished by their short spire, large body-whorl, long 

 aperture, recurved canal, and expanded inner lip. Lastly, the 

 Olives (Oliva, fig. 392, a) and Eice-shells (Olivella) are char- 

 acterised by their cylindrical polished shell, with a short spire, 

 a long narrow aperture, notched in front, and an obliquely- 

 striated columella. The living Olives are tropical and sub- 

 tropical in their distribution, and the fossil species, except 

 for two or three Cretaceous species of Olivella, commence in 

 the Eocene Tertiary. Ancillaria (fig. 392, b), datmg from 

 the Eocene, is nearly related to OUva, but the spire is pro- 

 duced, and wholly covered with enamel. 



Fam. 4. CoNiD^. — Shell inversely conical, with a long 

 narrow aperture, the outer lip notched at or near the suture. 

 The Conidm commence in the Cretaceous rocks, abound in 

 the Tertiaries, and attain their maximum at the present day. 



The true Cones form the genus Gonus (fig. 392, c), and 

 are distinguished by their short spire and regularly conical 

 shell, of which the outer lip is notched near the suture. 

 The Cones are represented in the Chalk, but are mainly 

 Tertiary and Eecent. Gosavia comprises Cones with a 

 plaited columellar lip, and is essentially a Cretaceous type. 

 The genus Pleurotoma (fig. 392, d) is distinguished by a 

 spindle-shaped shell, with a long spire, the outer lip having 

 a deep slit near the suture. The genus commences in the 

 Chalk, and has an enormous development in the Tertiaries, 



