214 



MANUAL OF THE MOLLUSCA. 



Cerith. radulum and granulatum of tlie West African rivers 

 approach very near tlio fossil potamides, but they have numerous 

 varices. 



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

 VIII., Pig. 23. 



Shell without varices, canal straight. Chusan. 



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

 resembles this section, and retains its spiral red bands. 



Nerin^a, Defrance. 



Etymology, nereis, a sea-n^nnph. 



Example, N. trachea. Fig. 98. 



Shell elongated ; many-whorled, nearly cylindrical ; 

 aperture channeled in front ; interior with continuous 

 ridges on the columella and whorls. 



Fossil, 150 species. Inf. oolite — U. chalk. Britain, 

 France, Germany, Spain, and Portugal. They are 

 most abundant, and attain the largest size to tho 

 south ; and usually occur in calcareous strata, asso- 

 ciated with shallow-water shells. (Sharpe.) 



Suh-gt'nera. 1. Nerincea. Folds simple: 2 — 3 on 

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

 or perforated. Above 50 species. 



2. iVerme/Za (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 (Sharpe), cohimella solid or perforated, 

 Fig. 98.» usually with 3 folds ; outer wall with 1 — 3 folds, some 



of them complicated in form. 



? 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 aporrhcoy 

 to flow away. 



* Fig. 98. Nenntea trachea, Desl., partly ground clown to show the fonn of the 

 interior. BaUx oolite, Eanville. Communicated by John Morris, Esq. 



