RissoiD^. 265 



As yet only known fossil in tertiary deposits. R. variculosa, 

 Desh. (Ixxii, 50). 



Nevillia, H. Adams. 



Dedicated to Mr.G-eofFrey Nevill,an Anglo-Indian conchologist. 



Distr. — 2 sp. Mauritius, Isle of Bourbon. N.picta^ H, Adams 

 (Ixxi, 52;. 



Shell imperforate, acutel}^ ovate ; whorls convex, spirally 

 Urate, longitudinally striate ; aperture oval ; columella callous, 

 toothed ; lip acute, smooth within, varicose outside. 



This geuus has much the appearance of a minute species of 

 Craspedotus, but there is no indication of nacre within the aper- 

 ture, and the tooth on the columella is more like that of Rissoa 

 monodonta ; in form and sculpture Nevillia approaches Alvania. 



PxjTiLLA, A. Ad., 186t. 



Didr. — P. lucida, A. Ad. (Ixxii, 51). Japan. 



Shell turbinately conoidal, solid, smooth, rimate ; aperture 

 suborbicular ; lip thickened, subeffuse in front, scarcely ex- 

 panded. Family relationship obscure. 



Subfamily HYDROBIIN^. 



Shell very small, or of moderate size, never exceeding two- 

 fifths of an inch in length, globose, ovate, or elongated, generally 

 ' umbilicated or rimate, and covered with a periostraca for the 

 most part of an olive-color ; whorls moderately numerous (4-8), 

 smooth, or, rarely, ribbed or carinated, never cancellated ; aper- 

 ture more or less ovate or rounded, rarely subacute or effuse 

 anteriorly ; peritreme continuous ; outer lip usually simple and 

 acute. Operculum paucispiral, corneous. Tentacles, verge and 

 gills as in the diagnosis of the family (p. 259). Foot without 

 lateral sinuses, truncate and auricled in front, and generally 

 rounded behind ; operculigerous lobe destitute of cirri. Station, 

 in fresh and brackish water. 



Like all of the Rissoidse these little animals are strictly her- 

 bivorous. Moquin-Tandon remarks that they have, connected 

 with the stomach, a cartilaginous stylet like that occurring in 

 certain bivalves. Something like this stylet Stimpson has 

 observed also in our American Melanians. 



LiTTOniNELLA, Braun. 

 Syn. — Paludinella, Loven (not Pfeiffer). Littorinidea, Eyd. 

 and Soul. 



Distr. — World-wide, brackish or sea-water, in sheltered posi- 

 tions. L. minuta, Totten (Ixxii, 53). 



Shell ovate or elongated, thin, smooth, perforate ; whorls 

 ventricose ; apex obtuse ; aperture rather broadly oval ; inner 

 lip not thickened. Operculum corneous. 

 18 



