CLA8S IV 



GASTROPODA 



533 



^ 



Family 13. Neritopsidae Fischer. 



Shell oval to semi-globose, with short, sometimes laterally twisted spire, and without 

 ■mnbilicus vr nacreous layer. Body ivhorl very large; aperture oval or semicircular, 

 Inner lip callous, curved and occasionally notched. Operculum calca- 

 reous, not spiral, with sub-central nucleus, and internally with callous 

 cohimellar margin, vAich forms a broad, angular or rounded process in 

 the middle. Devonian to Recent. 



The Neritopsidae are distinguished from the closely related 

 Neritidae, principally by the totally ditterent, non-spiral operculum, 

 and by the fact that the internal partitions are not resorbed, as in 

 the latter family. Detached opercula have been described under the 

 names of Peltairon, Scaphanidia, Cyclidia and Ehynchidia. 



Naticopsis M'Coy {Neritomopsis Waagen) (Figs. 897-899). Shell oval to globose, 

 smooth or transversely striated. Aperture oval ; inner lip flattened, somewhat 



Pif!. S97. 



Naticopsis mandel- 

 sluhi (Klipstein). 

 Keuper ; St. Cas- 

 sian, Tyrol. 



Fig. S9S. 

 A, Naticopsis ampUata Phil. Carboniferous ; Vise, Belgium. 

 B, Operculum of N. ylanispini Pliil., from same locality (after de 

 Koniuck). 



Fii;. siiy. 



Naticopsis lemniscata Hoernes. Trias ; 

 Esino, Lombardy. Original coloration 

 preserved. 



callous, curved and sometimes transversely striated. Sparse in Devonian, but very 

 common in Carboniferous and Trias. 



Hologyra Koken. Semi-globose, smooth, with faintly impressed sutures. Spire 

 short, laterally situated, not resorbed internally. Inner lip flattened, callous, covering 

 the umbilicits, and with sharj) margin. Abundant in the Trias. Some species, such 

 as H. neritacea (Mtlnst.), have the original colouring admirably preserved. 



Marmolatella Kittl. Auriform to cap-shaped, with very short, incurved and 

 almost marginal sjaire. Last whorl much distended ; inner lip callous, broad, 

 arched. Trias. M. stomatia (Stopp.), M. telleri (Kittl). 



Natiria de Koninck. Silurian to Carboniferous. Palaeonarica Kittl {Pseudo- 

 fossarus Koken). 



Naticella Mitnst. (Fig. 900). Thin-shelled, depressed, with straight spire, and 

 large, transversely ribbed body whorl. Trias. 



NaticrUa costata Miinster. 

 Uppei- Trias ; Wengen, South- 

 ern Tyiol. 



A, Ncritopsis moniliformis Grat. 

 Miocime ; Lapugy, Transylvania. I!, 

 N. spiiwsa'Hih. et Deslong. Callovian ; 

 Montreuil-Bellay, Maine-et-Loire. 



Pi(i. 902. 



Operculum of Neritopsis radula. 

 Recent; New Caledonia. External 

 and internal aspects (after Crosse). 



Vi- 



