SUB-ORDER B 



PLATYPODA 



461 



Platyceras, Conrad (Acroculia, Phil.), (Fig. 887). Apex bent and spirally inrolled. 

 Surface smooth, striated, plicated, or covered with small spines. Cambrian to Trias. 

 The fusion of this genus with Capulus, as proposed by some authors, is hardly 

 justifiable. 



Platyostoma, Conrad (Strophostylus, Hall), (Fig. 888). Shell composed of numerous 

 rapidly widening whorls. Spire low, body whorl very large. Inner lip reflected and 

 somewhat thickened. Aperture round, of large size. Silurian to Carboniferous. 



FIG. 887. 



I'l, it !icc rat, nr.ritoidus, Phil. Car- 

 boniferous ; Vise, Belgium. 



I'fut i/ostoma, niaqarensis, 

 Hall. Devonian ; Waldron, 

 Indiana. 



Horiostoma Jiarrandei, Mun.-Chalm. 

 Lower Devonian ; Gahard, Ille-et- 

 Vilaine (after Munier-Chalmas). 



Horiostoma, Mimier-Chalm. (Fig. 889). Shell thick, spirally ribbed, with short 

 lateral spire, and wide umbilicus. Devonian. 



Tubina, Barr. Silurian. Rothpletzia, Simonelli. Tertiary. 



Hipponyx, Defr. (Cochlolepas, Klein), (Fig. 890). Shell thick, obliquely conical to 

 cup-shaped. Beak straight, rarely spiral, greatly removed posteriorly. Aperture oval or 

 A rounded, internally with a horseshoe-shaped muscular impression. The foot 



often secretes a thick, operculiform calcareous disc. Cretaceous to Recent. 



Galerus, Gray (Calyptraea, p.p. Lam.). 

 Shell thin, conical, with central spiral 



FIG. 890. 



Hipponyx cornucopiae, Lain. Cal- 

 caire Grassier ; Liancourt, near 

 Paris. A, Shell. B, Foot-plate. 



FIG. 891. 



Creptdvla trnmti- 



formis, Lain. Plio- 

 cene ; Tuscany. 



FIG. 892. 



Cnlyptraea trnchiformis, Lam. 

 DamiM-y, near Epernay. 



Calcaire Grossier ; 



apex. Whorls flattened, often spinose. Base horizontal; aperture wide, depn .->.<!. 

 Cretaceous to Recent. 



Crepidula, Lam. (Fig. 891). Slipper-shaped, elongate-oval, flat or arched. Beak 

 at the posterior end, almost marginal, somewhat curved. Aperture greatly elongated, 

 wide ; inner lip formed by a thin horizontal lamella. Cretaceous to Recent. 



Grucibulum, Schum. ; Calyptraea, Lam. (Fig. 892). Tertiary and Recent. 



Family 5. Naticidae. Forbes. 



Shell with short spire and large body whorl. Aperture semi-circular to oval, angular 

 posteriorly, broadly rounded anteriorly. Operculum calcareous or horny, paucispiral. 

 Marine. Trias to Recent. 



The distinction of fossil Naticidae from Naticopsis, Nerita, and Ampullaria is 



