CLASS IV 



GASTEOPODA 



537 



deei) ; aperture higher than wide, with shallow canal. Silurian to Trias ; particularly 

 abundant in the Carboniferous. 



Zijgo2)leara Koken. Like the last, but whorls with sharp, slightly curved 

 transverse ribs, or transverse nodose keel. Devonian to Lower Cretaceous. 



Bourgetia Deshayes {Pithodea de Kon.). Large, 

 elongate-oval to turreted, with large, inflated body 

 whorl. Surface marked with spiral striae or furrows. 

 Carboniferous and Upper Jura. 



Pseudomelania Pictet {Chcmnitzia p.p. d'Orbigny) 

 (Fig. 913). Turreted, with 

 numerous, almost flat whorls, 

 and slightly impressed sutures. 

 Surface smooth, or marked by 

 fine growth - lines ; aperture 

 rounded anterioi'ly, or with 

 faint canal. Umbilicus want- 

 ing; rarely an umbilical fissure 

 present. Very abundant in the 

 Trias and Jura, less so in 

 Cretaceous and Eocene ; prob- 

 ably present also in the Car- 

 boniferous. 



Subgenera : Oonia, Microscldza 

 Gemm. ; IIypsipleu7'a, AndptycMa ^^^ ^^^ 



Koken. Trias and Jura. Goe- 



lostyhnc^ _ Euslylus, SpirostT/lus ^j^^j^,^^,, .,_ j^u^l^jl, ^e- 

 Kittl. Trias, hayania Munier- vonian; Paftrath, near 

 Clialni. (Fig. 914). Eocene. Cologne. 



Fici. 913. 



Pseudomelania 

 h p d d, ingt one n s I s 

 (Sowl).). Oxlbid- 

 iau ; Franco. Bands 

 of original colora- 

 tion still showing. 



Pseudmnalania 

 (Bayania) lactea 

 Lam. sp. Cal- 

 caire Grossier ; 

 Grignon, near 

 Paris. 



Pustularia Koken, non Swains. Turreted, with groove -like sutures. WhorLs 

 flat, with three or more spiral rows of nodes. Trias. 



Gatosira Koken. Wliorls flat, with transverse ridges. Aperture canaliculate ; 



base with spiral grooves. Trias and Jura. 



Diastoma Desh. (Fig. 915). Like the last, 

 but aperture separated from the body whorl. 

 Whorls with transverse folds and spiral striae. 

 Cretaceous to Recent. 



Mathilda Semper (Promathilda Andreae). 

 Turreted ; whorls transversely and spirally 

 striated or ribbed. Aperture with canal. Proto- 

 conch heterostrophic. Jura to Recent. 



Keilostoma Desh. {ParypJiostoma Bayan) (Fig. 

 916). Turreted, spirally striated. Outer lip 

 with externally thickened margin. Eocene. 



Turhonilla Risso (Ghemnitzia p.p. d'Orb.) (Fig. 

 9 1 7). Small, turreted, with heterostrophic proto- 

 conch. Whorls transversely ribbed or smooth. 

 Inner lip straight, or occasionally with folds. 

 Tertiary and Recent 



Odostomia 

 Lamarck (Fig. 919). 

 Tertiary and Recent. 



Fio. 915. 



Diastoma costellata 

 (Lam.). Caloaire 

 Grossier ; Uamery, 

 near Epernay. 



Fig. 916. 



Keilostoma turricula 

 Brug. sp. {Mclanla 

 marginata Lamarck). 

 Caloaire Grossier; 

 Grignon, near Paris. 



Fleming 



(Fig. 918); Pyramidella 

 Cretaceous to Recent. 

 Palaeoniso Gemm. Trias 



Syrnola Adams ; Eulimella Fischer, 

 and Jura. 



The genera Suhulites Conrad (? Polyphemopsis Portlock), from the Cambrian t^ 



