TURBONILLID^. 235 



Didr. — 50 sp. World-wide. Range from low-water to 

 90 fathoms. Fossil. Cretaceous — . T. elegantissima, Mont. 

 (Ixviii, 98). 



Shell slender, elongated, many-wborled ; whorls plaited ; apex 

 sinistral ; aperture simple, ovate ; peristome incomplete, colu- 

 mella not plaited. Operculum horn 3'-, subspiral. 



Animal. Head very short, furnished with a long, retractile pro- 

 boscis ; tentacles triangular ; ejes immersed at the inner angles 

 of the tentacles ; foot truncated in front, with a distinct mentum, 

 operculigerous lobe with a minute conical appendage on each side. 



Comprises a great number of small, graceful white shells which 

 have been grouped in a number of genera or subgenera. 



MORMULA, A. Ad. Subulately-turreted, rissoid, solid, thick, 

 longitudinally plicate ; aperture large, columella spirally tortuous, 

 lip thickened within, margin acute. A few Japanese species. 

 T. risaoina, A. Ad. 



DUNKERiA, Carpenter, 1857. (In honor of W. Dunker, a dis- 

 tinguished German conchologist. ) Whorls rounded, cancellated. 

 Numerous species. Mazatlan, Japan. T. paucilirata^ Carp. 

 Mazatlan. 



VANESiA, A. Ad., 1861. Proposed for two species resembling 

 Melania in external characters, but true marine shells, decussated 

 hj longitudinal and spiral ridges. T. trifasciata^ Sowb. China. 



SPiROCLiMAX, Morch. Subcylindrical, pellucid, suture con- 

 tabulate, aperture ear-shaped, lip thickened, sigmoidal, sub- 

 marginate, inflexed at the suture. 1 sp. West Indies. 



MiROBELi-cus, Saudb. T. inaspecta, Fuchs. 



Streptacis, Meek, 1871. 



Disfr.—S. WliitfieMi, Meek. Carb. ; Ills. 



Shell small, turreted, smooth; embryonal whorls planorbiform ; 

 mouth oval. 



HoLOPELLA, M'Coy, 1852. 



Etym. — ''olos^ entire, and ope, an aperture. 



Distr. — Fossil, 12 sp. Silurian, Trias; Europe, United States. 

 H. gregaria, Sowb. 



Shell elongated, slender, of numerous graduallj^ increasing 

 whorls, generally crossed by slightly arched striae ; mouth cir- 

 cular, with the peristome entire ; base rounded, with or without 

 a minute umbilicus. 



The shells of the species composing this genus differ from 

 those of Turritella in the continuous peristome and definite 

 round margin to the aperture, thus approaching much nearer to 

 Scalaria. 



EuLiMELLA, Forbes. 



Dist7\ — Eur., Japan. E. Scillse, Scacchi (Ixviii, 1, 2). 



Shell elongated, turriculate, solid, smooth, polished, whorls 



