202 GASTROPODA. [Pectinibranchia. 



Diameter, 1-9 mm. ; height, 4mm. 

 Animal unknown. 

 Type in my collection. 



Hob. Snares, in 50 fathoms (Captain Bollons). 

 Remark. In general appearance this species recalls Rissoina sub- 

 fusca, Hutton, which, however, is quite smooth. 



Subgen. 2. ALVANIA, Kisso, 1826. 



Alvania, Risso, Hist. Nat. Eur. Merid., iv, 1826, 146. Type : R. cimex, L. 

 Acinus, Monterosato, 1884. 



Shell oval, turbiniform ; spire short, with sharp apex ; whorls 

 rounded, nodulously cancellated ; aperture subcircular, crenulated or 

 grooved within ; outer lip margined exteriorly by a varix. 



KEY TO SPECIES. 



A. Spirals not numerous, 3 to 4 on the penultimate whorl. 



a. Penultimate whorl with 3 spirals ; whorls 7 ; spire 2 



times the height of the aperture . . . . cheilostoma.. 



aa. Penultimate whorl with 4 spirals ; whorls 4^ ; spire 



little higher than aperture . . . . . . pingue. 



B. Spirals numerous, more than 4. 



a. Shell elongate, slender ; whorls slightly convex, the last 

 not inflated ; spire li times the height of the aper- 

 ture . . . . . . . . . . . . candidissima. 



aa. Shell ovate ; whorls strongly convex, the last somewhat 



inflated ; spire twice the height of the aperture . . exserta. 



5. Rissoa candidissima, Webster, 1905. Plate 12, fig. 5. 



Rissoa candidissima, Webster, T.N.Z.I., xxxvii, 1904 (1905). 278, pi. 10, f. 7. 



Shell thin, imperforate, semi transparent. Sculpture : About 12 dis- 

 tant axial riblets on the body-whorl, crossed by 12 spiral liree. Colour 

 white. Spire elevated conic, about 1-| times the height of the aper- 

 ture ; outlines slightly convex. Protoconch of 2 smooth elevated and 

 convex whorls. Whorls 4|, slightly convex ; base somewhat flattened. 

 Suture deep. Aperture vertical, rounded. Peristome discontinuous, 

 straight, slightly thickened. Operculum unknown. 



Diameter, 1 mm. ; height. 2 mm. 



Animal unknown. 



Type in Mr. W. H. Webster's collection. 



Hal). Takapuna (type). 



6. Rissoa cheilostoma, Tenison-W T oods, 1877. Plate 12, fig. 6. 



Rissoa cheilostoma, T. - Woods. P.R.S. Tasm., 1876 (1877). 152; Man. 

 Conch. (1). ix, 306, pi. 68, f. 91. ^?. plicata, Hutton, C.M.M., 29; not 

 of Deshayes, 1838. Rissoina plicata, Hutt., M.N.Z.M., 80. Eglisia 

 plicata, Hutt., P.L.S. N.S.W., ix, 939. Rissoia plicata, Hutt. : Suter, 

 P. Mai. S., iii. (i R. cheilostoma, T. - Woods. Pritchard and Catliff, 

 P.R.S. Vic., xiv (n.s.). 107. 



Shell very small, turriculate, imperforate, clathrate, white. Sculp- 

 ture consisting of 2 spiral line, increasing to 3 on the penultimate 

 whorl, crossed by rather distant radiate riblets. about 15 on the 



