CLA8S IV 



GASTROPODA 



533 



Family 13. Neritopsidae Fischer. 



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

 umbilicus or nacreous layer. Body whorl very large ; aperture oval or semicircular, 

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

 reous, not spiral, with suh-central nucleus, and internally lüith callous 

 colr.mellar margin, which forms a hroad, angular or rounded process in 

 the middle. Devonian to Recent. 



The Neritopsidae are distiiiguished from the closely related 

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

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

 the latter family. Detached operciila have been described under the 

 nanies of Peltairon, Scaphanidia, Cyclidia and Rhynchidia. 



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

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



A B 



% 



Fio. S97. 



Naticopsis mandel- 

 slohi (Klipstein). 

 Keuper ; St. Cas- 

 sian, Tyrol. 



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

 B, Operculum of N. planispira Phil., from sarae locality (after de 

 Koninck). 



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 umbilicus, and with sharp margin. Abundant in the Trias. Some species, such 

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



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

 almost marginal spire. 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 Münst. (Fig. 900). Thin-shelled, depressed, with straight spire, and 

 large, transversely ribbed body whorl. Trias. 



Fio. 900. 

 Naticella costata Münster. 

 Upper Trias; Wengen, Soutli- 

 eru Tyrol. 



Fio. 901. 



A, Neritopsis monillfoi-mis Grat. 

 Miocene ; Lapugy, Transylvania. B, 

 N. spinosa Heb. et Deslong. Callovian ; 

 Montnniil-Bellay, Maine-et-Loire. 



Fio. 902. 



Operculum of Nerito]ms raJiihi. 

 Recent; New Caledonia. Bxternal 

 and int«'rnal aspects (aft«'r Citisse). 



