Risso't.] GASTROPODA. '20l 



3. Rissoa impressa, Hutton, 1885. Plate 12, fig. 3. 



Rissoa impressa, Hutton. T.X.Z.I.. xvii, 1884 (1885), 321 ; Plioc. M., 64, 

 }il. 8, f. 64; Suter, T.X.Z.I., xxxix, 257. Rissoina agrestis, Webster, 

 T.N.Z.I., xxxvii, 1904 (1905), 279, pi. 10, f. 10. 



Shell minute, ovate, imperforate, solid, costate, with a distinct 

 groove below the suture. Sculpture consisting on the last 3 whorls 

 of rather stout rounded axial riblets, about 20 on the last whorl, ex- 

 tending over the base ; they are slightly oblique on the upper whorl, 

 but distinctly so on the body-whorl, .directed backwards ; the in- 

 terstices are slightly narrower and smooth ; the riblets are crossed 

 by a distinct groove a little below the suture, and usually of the same 

 depth as the latter, reducing the riblets between suture and groove 

 to flat nodules ; the protoconch is microscopically minutely reticulated, 

 the fine spirals distinct. Colour of a purple-brown, shading to cream 

 colour on the body-whorl. Spire elevated conic, about twice the 

 height of the aperture ; outlines slightly convex. Protoconch of 2 

 convex whorls, dome-shaped. Whorls 5, the last 2 rather rapidly in- 

 creasing, flatly convex ; base rounded. Suture not much impressed. 

 Aperture roundly ovate. Peristome continuous, thickened, slightly 

 expanded, with a sharp edge, white and shining. Columella short, 

 arcuate, and thick. Operculum unknown. 



Diameter, 1-2 ram. ; height, 2*3 mm. 



Animal unknown. 



Type, from the Pliocene of Petane, in the Canterbury Museum, 

 Christchurch. 



Hob. Takapuna Reef (W. H. Webster) ; near Little Barrier Island, 

 in 20 fathoms (R. H. Shakespear) ; near Channel Island, Hauraki 

 Gulf, in 25 fathoms ; Cape Maria van Diemeu. 



Fossil in the. Pliocene of Petane, Wanganui, and Waikopiro. 



4. Rissoa rufoapicata, Suter, 1908. Plate 12, fig. 4. 



Rissoa rufoapicata, Suter, P. Mai. S., viii, 28, pi. 2, f. 21. 



Shell small, elongately oval, rimate, solid, costate, shining. Sculp- 

 ture : The embryonic whorls smooth, the succeeding ones closely 

 Axially ribbed, the riblets, first faint and inconspicuous, are getting 

 much stronger as growth proceeds ; they are flat, close together, with 

 smooth and slightly narrower interstices, flexuous, nearly vertical 

 on the upper whorls, but obliquely directed backward on the last 

 whorl, and extending over the base. Colour : The first 2 or 3 whorls 

 are rufous or purple, the following 2 dark grey, and the last whitish. 

 Spire elevated conical, 2 times the height of the aperture ; outlines 

 slightly convex. Protoconch papillate, of 2 . flatly convex whorls. 

 Whorls 6, regularly increasing, flattish ; base convex. Suture deep, 

 slightly uneven. Aperture oblique, oviform, white. Peristome con- 

 tinuous, much thickened and expanded. Columella very short, arcuate. 

 A distinct umbilical chink is formed by the reflection of the inner lip. 

 Operculum unknown. 



