SUB-ORDER B 



RHIPIDOGLOSSA 



453 



callous, curved, and sometimes transversely striated. Sparse in Devonian, but v.-rv 

 common in Carboniferous and Trias, 



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

 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, Miinst. sp., 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. (Ostrea) stomatia, Stopp. sp. ; M. Telleri, Kittl. sp. 



Natiria, de Koninck ; Silurian to Carboniferous. Palaeonarica, Kittl. (Pseudo- 

 fossarus, Koken). 



Naticella, Miinst, (Fig. 851). Thin-shelled, depressed, with straight spire, and 

 large, transversely ribljed body whorl. Trias. 



Platychilina, Koken (Fossariopsis, Laube). Spire depressed, straight ; last whorl 



Southern Tyrol. 



FIG. 852. 



A, Neritopsis moniliformis, Grat. 

 ' - ' ' B,N. 



Montre'uil-Beliay, Maine-et-Loire. 



FIG. 851. 



Naticella costata, Miinst. Miocene ; Lapugy, TransylvanL. _, _.. 

 Upper Trias; Wengen, spinosa, Heb. Deslong. Callovian ; 



FIG. 853. 



Neritopsis radula. Recent ; 

 New Caledonia. A, External, 

 and B, internal aspect (after 

 Crosse). 1/1- 



large, surface rough, tuberculose. Inner lip even, with simple margin. Trias. P. 

 pustulosus, Miinst. sp. 



Delphinulopsis, Laube. Like the last, but spire composed of loosely connected 

 whorls. Sutures deep. Body whorl with nodose longitudinal keels. Inner lip even, 

 with sharp margin. Trias. D. binodosa, Miinst. sp. 



Neritopsis, Grat. (Figs. 852, 853). Spire depressed, body whorl very large. Sur- 

 face with spiral and transverse ribs or nodes, often cancellated. Inner lip thickened, 

 with broad, angular emargination in the middle. Trias to Recent. 



Family 14. Neritidae. Lamarck. 



Shell semi-globose, without umbilicus or nacreous layer. Spire very short, somewhat 

 lateral ; whorls rapidly broadening, the last very large, and earlier ones resorbed inter- 

 nally. Aperture semi-circular ; margin of the flattened or calloused inner lip often with 

 teeth. Operculum calcareous, with a lateral spiral nucleus, and a process for muscle 

 attachment on the inner side. Trias to Recent. 



The Neritidae are partly marine, and partly fresh-water inhabitants. The former 

 live usually in the vicinity of the coast, the latter often in brackish water. Since the 

 earlier whorls are internally resorbed, casts reveal no trace of the spire. This 

 character, together with the form of the operculum, serves to distinguish the 

 family from the Naticopsidae, from which both it and the terrestrial Helicinidae 

 are probably descended. Fossil forms not infrequently retain traces of their former 

 coloration. 



Neritaria, Koken (Protonerita, Kittl). Spire acuminate, suture deep, surface 

 smooth. Outer lip sharp ; inner lip callous, flattened. Resorption of the inner walls 

 incomplete. Trias. 



