244 



MATTUAl- OF THE MOLLUSCA. 



Cerith. radulum and granulatum of the West African rivers 

 approach very near the fossil potamides, but they have numerous 

 varices. 



Lampama, Gray (batillaria, Cantor). Cerith. zonale. PL 

 VIII., Fig. 23. 



Shell without varices, canal straight. Chusan. 



The fossil potamides decussatus, Brug., of the Paris babin, 

 resembles this section, and retains its spiral red bands. 



Nerin^a, Defrance. 



Etyiiiology, nereis, a sea-nymph. 



Example, N. trachea. Pig. 98. 



Shell elongated ; many-whorled, nearly cylindrical ; 

 aperture channeled in front ; interior with continuous 

 ridges on the columella and whorls. 



Fossil, 150 sj)ecies. Inf. oolite — U. chalk. Britain, 

 Prance, Germany, Spain, and Portugal. They are 

 most abundant, and attain the largest size to the 

 south ; and usually occur in calcareous strata, asso- 

 ciated with shallow-water shells. (Sharpe.) 



Sub-genera. 1. Nerincea. Folds simple: 2 — 3 on 

 the columella ; 1 — 2 on the outer wall ; columella solid, 

 or perforated. Above 50 species. 



2. JVenwe^^a (Sharpe), columella solid; folds simple; 

 columellar, — 1 ; outer wall, 1. 



3. Trochalia (Sharpe), columella perforated, with 

 one fold ; outer wall simple, or thickened, or with one 

 fold; folds simple. 



4. Ptygmatis (Sharj)e), columella solid or perforated, 

 usually with 3 folds ; outer wall with 1 — 3 folds, some 

 of them complicated in form. 



Fig. 98.* 



? Fastigiella, Eeeve. 



Type, F. carinata, Eeeve. 

 Shell like turritella; aperture with a short canal in front 

 (Cuming Museum, and British Museum). 



Fossil, Eocene. Paris [Cerithium rugosum. Lam.). 



Aporrhais, Aldrovandus. 



Etymology, aporrhais (Aristotle), " spout-shell," from aporrhcOf 

 to flow away. 



* Fig. 98. Nerinaa trachea, Desl,, partly ground down to show the form of tUe 

 Interior. Bath oolite, KauNille. Communicated hy John Moi-ris, Esq. 



