SUB-ORDER B RHIPIDOGLOSSA 453 
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, 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, Kitt]. (Pseudo- 
fossarus, Koken). 
Naticella, Miinst. (Fig. 851). Thin-shelled, depressed, with straight spire, and 
large, transversely ribbed body whorl. Trias. 
Platychilina, Koken (Fossariopsis, Laube). Spire depressed, straight ; last whorl 

Fic, 852. Fia. 853. 
Fic. 851. a. : diay de 7 + a ak ee : : 
A, Neritopsis moniliformis, Grat. Neritopsis radula. Recent ; 
Naticella costata, Munst. Miocene ; Lapugy, Transylvania. B, N. New Caledonia. A, External, 
Upper Trias; Wengen, spinosa, Heb. Deslong. Callovian ; and 8B, internal aspect (after 
Southern Tyrol. Montreuil-Bellay, Maine-et-Loire. Crosse). 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 wmbilicus 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. 
