Cerithidea.] GASTROPODA. 239 



Diameter, 10 mm. ; height, 29 mm. Angle of spire. 23. 

 Dentition. Button, T.N.Z.I., xv, 122, pi. 14, f. D. 



Type in the British Museum. 



Hob. Bay of Islands, type (DierTenbach). Common in the North 

 Island ; not found south of Banks Peninsula. 

 Fossil in the Pliocene. 



3. Cerithidea subcarinata, Sowerby, 1855. Plate 14, fig. 9. 



Cerithidea subcarinata, Sowerby, Thes. Conch., ii. 1855, 889, f. 287. Ceri- 

 thium australis, Gray, Dieff. N.Z., 241, not of Lamarck. Cerithidea 

 nigra, H. & J. : Hutton, M.N.Z.M., 74, not of Hombron and Jacquinot. 

 Potamides (Cerithidea) bicarinata, var. .subcarinata. Sow., Man. Conch. 

 (1). ix, 163. pi. 35. f. 16. 



Shell small, elongated, longitudinally plicate, base bicarinate. 

 Sculpture consisting of broadly rounded, slightly oblique axial ribs, 

 about 12 on the penultimate whorl ; sometimes a narrow spiral groove 

 below the suture is present ; the ribs are stopped at the periphery 

 of the base by a spiral groove taking its origin at the suture ; base 

 with 2 spiral ribs, the outer one strong and broad, the inner one, 

 around the base of the neck, short and narrow ; they are often cut 

 up into irregular nodules by incremental lines. Colour brownish- 

 black, often with a light-brown coating. Spire elevated conical, 

 about 2^ times the height of the aperture, outlines slightly convex. 

 Protoconch eroded. Whorls about 10, regularly increasing, flatly con- 

 vex ; base slightly concave. Suture impressed. Aperture oblique, 

 ovate, channelled above, produced at the base in a very short, oblique, 

 and truncated canal. Interior dark brown, sometimes with 1 or 2 

 lighter bands. Outer lip convex, slightly thickened and expanded, 

 not very sharp. Columella slightly concave, base truncated. Inner 

 lip sharply marked off, and extending over the body to the outer 

 lip, but prevented from reaching it by the narrow channel. Operculum 

 normal. 



Diameter, 4-25-5-5 mm. ; height, 11 -5-14 mm. Angle of spire, 30. 



Dentition. Hutton, T.N.Z.I., xv, 123, pi. 14, f. E. 



Type in the British Museum. 



Hob. Throughout New Zealand, and at the Chatham Islands. 



4. Cerithidea tricarinata, Hutton, 1883. Plate 14, fig. 10. 



Cerithidea tricarinata, Hutton; N.Z.J.S., i, 1883, 477; T.N.Z.I., xvi, 214. 



Shell small, turreted, longitudinally plicate and spirally grooved. 

 Sculpture consisting of strong, rounded, subnodulose, longitudinal 

 ribs, 10 to 15 on the penultimate whorl, stopped on the body-whorl 

 by a spiral sulcus on the periphery of the base ; spire- whorls and 

 posterior half of the body-whorl with 3 or 4 spiral grooves, sometimes 

 reduced to 2 ; base with 3 subequidistant well-marked spiral ridges, 

 with occasionally others on the neck. Colour brown. Spire elevated, 

 about three times the height of the aperture ; outlines faintly convex. 



