542 



MOLLUSCA 



PHYLÜM VI 



Hipponix Defr. (Gochlolepas Klein) (Fig. 939). Shell tliick, obliquely conical to 

 cup-shaped. Beak straiglit, rarely spiral, greatly removed pos- 

 teriorly. Aperture oval or rounded, internally with a horseslioe- 

 shaped miiscular imj)ression. The foot often secretes a thick, 

 operculiform calcareoiis disk. Cretaceous to Kecent. 



Hipponix cornucopiae (Lamarck.) Calcaire 

 Grossier; Liancourt, near Paris. A, Shell. 

 B, Foot-plate. 



Fig. 940. 



Calyptraea (Trochita) trocJiiformis Lam. Calcaire Grossier ; 

 Damery, near Epernay. 



Calyptraea Lam. {Galerus Gray) (Fig. 940). Shell thin, conical, with central 

 Spiral apex. AVhorls flattened, often spinöse. Base horizontal : 

 aperture wide, depressed. Cretaceous to Eecent. 



Grepidula Lam. (Fig. 941). 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 Eecent. 



Crucihulum Schum. Tertiary and Recent. 



Family 5. Naticidae Forbes. 



Fig. 941. Shell with short spire and large hody whorl. Aperture semicircular 



Crepiduia ungui- to oval, angular posteriorly, hroadly rounded anteriorly. Operculum 

 ceneT Tu^cany. ^°" calcareous or horny, paucispiral. Marine. Trias to Recent. 



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

 attended with some difßculty, since they frequently possess nearly identical characters 

 in common, differing mainly in the operculum, whicli is not preserved fossil. 



Sinum Bolten {Sigaretus Lam.) (Fig. 942). Shell depressed, auriform, spirally 



Fig. 942. 



Sinum haliotoideum 

 (Linn.). Miocene ; Grund, 

 Hungary. 



Fig. 943. 



A, Natica millepunctatu Lam, 

 Pliocene ; Monte Mario, near Roma. 

 -B, Operculum of N. multipunctata 

 S. Woodvv. Crag ; Sutton. 



Fig. 944. 



Natica (Ampullina) patula 

 Lam. Calcaire Grossier ; 

 Damery, near Epernay. 



striated or furrowed. Spire very low, with rapidly widening whorls. Aperture greatly 

 distended ; operculum horny. Tertiary and Recent. 



Natica Scopoli (Figs. 943-946). Globose, semi-globose, ovate or pyramidal, smooth 

 and lustrous, rarely spirally striated, umbilicate or not. The umbilicus, when 



