43-! GASTROPODA. [Pectinibranchia. 



all whorls except the protoconch, and a peripheral band on the body- 

 whorl ; d, dark brown with distant triangular white spots below 

 the suture on the last 3 whorls, sometimes accompanied by a band 

 below the periphery of the last whorl, composed of close white spots ; 

 e, yellowish or greenish-white with longitudinal fiexuous brown lines 

 they may form a brown peripheral band on the spire-whorls and one 

 on the base of the body-whorl. Epidermis thin, but faintly shining. 

 Spire elevated and narrowly conic, of the same height as the aperture 

 or but slightly higher ; outlines straight or very lightly convex. Proto- 

 conch of 1|- smooth whorls, nucleus depressed globose. Whorls 6, 

 regularly increasing, but faintly convex ; base slightly contracted 

 below. Suture linear. Aperture subvertical, narrow, moderately 

 channelled above, open and truncated below, slightly notched. Outer 

 lip somewhat thickened and smooth or crenate within, straight, 

 and curved towards the base. Columella straight, a little twisted 

 below. Inner lip narrow, with a sharp free edge in adult specimens. 

 According to Hutton, there is no operculum. 



Diameter, 3 mm. ; height, 6-5 mm. 



Animal yellowish-white, with a narrow black longitudinal line on 

 the back of the head, between the eyes ; some scattered dead- white 

 spots on the body and siphon. Tentacles thick, not tapered, ap- 

 proximated ; the eyes at their outer bases. Siphon curved. Foot 

 expanded in front and notched at each side. (Hutton. T.N.Z.I.. xiv, 

 163, pi. vii, f. 0.) 



Dentition (Hutton, I.e., 163, pi. 7, f. P). Formula 1+0 + 1; the 

 central portion of the radula is thickened, and divided transversely 

 into membranous plates, which are broader than long, but the plates 

 bear no teeth. The lateral teeth are versatile ; they are curved, 

 pointed at the end. and with 2 denticles on the concave side. 



Type in the British Museum (Cuming collection). 



Hab. Throughout New Zealand, under stones and on seaweeds, 

 near low-water mark to a depth of about 20 fathoms. 



Remarks. The specimens from deep water are much smaller, the 

 height sometimes not more than 4 mm. Hutton's P. flexuosa is the 

 colour variety mentioned under e. The operculum and also the central 

 tooth of the radula being usually very small, they may have been 

 overlooked. Iredale found constantly a dark shell paired with a light 

 one, and thinks that the change of coloration in this species may be 

 a sexual characteristic. 



Fossil in the Pliocene. 



2. Mitrella leptalea, Suter, 1908. Plate 19, fig. 14. 



Mitrella leptalea, Suter, P. Mai. S., viii, 1908, 180, pi. 7, f. 6. 



Shell small, subulate, smooth, shining, thin, pellucid, yellowish. 

 Sculpture consisting of almost obsolete fine microscopic spiral striae 

 and a few faint spiral ridges on the lower part of the base ; growth- 



