CLASS IV 



GASTEOPODA 



)27 



Stra'parollina Billings. Cambrian. Ophileta Vanuxem. Cambrian to Silurian. 

 Maclurea Lcseuenr ; Maclurina Ulr. and Scof. Ordovician and Silurian. 



Platyschisiiut M'Coy. Thin - shelled, depressed 

 conical, smooth. Umbilicus relatively narrow ; outer 

 lip with broad sinus. Silurian to Carboniferous. P. 

 helicoides Sowb. Carboniferous. 



StraparoUus Montf. (Fig. 862). Turbinate to 

 discoidal, with broad umbilicus. Whorls smooth or 

 with fine transverse striae. Silurian to Jura ; especially 

 abundant in Devonian and Carboniferous. 



Phanerotinus Sowb. Like the last, except that the 

 whorls form an open spiral. Carboniferous. 



Euomphalus Sowb. {Pleuronotus Hall ; Schizostoma 

 Bronn) (Fig. 863). Depressed conical to discoidal, with wide umbilicus. Spire 

 flattened or even concave sui^eriorly ; whorls angular, the edges sometimes set with 

 nodes (Phymatifer de Kon.). Outer lip with emargination at the ujiper angle. Silu- 

 rian to Trias ; maximum in Carboniferous. 



A B 



Fui. 862. 



StraparoUus dionysii Montf. 

 Carboniferous ; Vise, Belgium. 



Fio. 863. 



Euomphalus catUlus (Sowb.). Carboniferous ; Kiklare, Ii'eland. 

 -4, Superior, and B, Inferior aspect. 



Fio. 864. 



Discohclix orhis Renss. Middle Lias : 

 Hiuter-Schafberg, Austria. 



Subgenera : Omplmlocirrus de Ryckholt. Devonian and Carboniferou.s. Cocluccnlrus 

 Zittel. Trias. 



Discohelix Dunk. (Fig. 864). Flat, discoidal ; upper side flat or slightly concave, 

 the lower widely umlnlicate. Whorls rectangular, with sharp edges. Trias to 

 Oligocene. 



Ecryliompliahhs Portlock ; Eccyliopterus Remele ; Helicotoma Salter. Ordovician 

 and Silurian. 



Family 5. Raphistomidae Ulrich and Scofield. 



Comprising shells intermediate hetioeen the Euoviphalidae and Pleurotoviariidae, and 

 regarded as ancestral. to these families and the Trochidae. 



Raphistoma Hall. Shell depressed or completely flattened ; whorls angular above ; 

 umbilicus moderately broad ; outer lip with short notch on the keel. Ordovician 

 and Silurian. 



Enomphalopterus Roemer. Distinguished by its more rounded volutions and 

 excessively developed carinae. Silurian. 



Scalites Emmons, non Conrad. Turbinate, spire only moderately high and 

 acuminate ; whorls flattened superiorly, rising steplike one above the other, sharply 

 angular at the periphery, produced below. Body whorl very large, smooth ; aperture 



