PYRAMIDELLID^. 239 



Shell turriculated, spire elevated, longitudinally ribbed ; colu- 

 mella with three anterior plications ; outer lip sharp, sometimes 

 plicate within. 



The Pj'ramidellae live in sandy bays and on shallow mud- 

 banks, concealing themselves under the surface, and indicating 

 their presence b}' the formation of slender raised tracks. 



OBELTScus, Humphrey. Differs from Pyramidella in being 

 smooth instead of ribbed. P. maculosa, Lam. (Ixviii, 12). 



TiBERiA, Jeffre3^s. Shell nmbilicated. P. minuscula, Monts. 

 Deep Sea. Mediterranean. 



LONCH^us, Morch. Shell imperforate, last whorl with a median 

 sulcus. 



TRIPTYCHUS, Mdrch. Shell subulate, paucilirate spirally ; aper- 

 ture Urate within; columella with three small anterior plications. 



Nerin^a, Defrance. 



Etym. — Nereis, a sea-n3rmph. 



Syn. — Itruvia, Stolicz. Itieria, Matheron. 



Disti\ — Fossil, 150 sp. Jurassic, Cretaceous; Britain, France, 

 Germany, Spain, and Portugal. They are most abundant, and 

 attain the largest size to the south ; and usually occur in calca- 

 reous strata, associated with shallow-water shells. N. trinodosa, 

 d'Orb. (Ixviii, 10'. N. trachea, Desh. (Ixviii, 13). 



Shell elongated; many-whorled, nearl}^ cylindrical ; aperture 

 channeled in front ; interior with continuous ridges on the 

 columella and whorls. 



NERiN^A (restricted). Folds simple: 2-3 on the columella; 

 1-2 on the outer wall ; columella solid, or perforated. Above 

 50 sp. 



nerinella. Sharp. Columella solid ; folds simple; columellar, 

 0-1 ; outer wall, 1. 



TROCHALiA, Sharpc. Columella perforated, with one fold ; 

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



PTYGMATis, Sharpe. Columella solid or perforated, usually 

 with 3 folds ; outer wall with 1-3 folds, some of them compli- 

 cated in form. 



HALLOYSiA, Briart and Cornet. Shell elongated, turriculated, 

 whorls numerous, axis widely perforated, aperture rounded or 

 subquadrangular, columella biplicated. H. biplicata, B. and C. 

 (Ixviii, 14). Calcaire grossier of Mons, Belgium. 



SoLENiscus, Meek and Worthen, 1860. 

 Etym. — Soleniskos, a little channel or gutter. 

 Distr.—S. typicuH. Upper Coal Measures ; Springfield, Illinois. 

 Shell fusiform, smooth, body-whorl contracted below into a 

 distinct straight canal, with an oblique plait on the columella. 

 Agrees with Macrocheilus in its smooth surface and columella- 



