120 GASTROPODA. [Aspidobranchia. 



5 in number. Colour black or greenish-black, dotted upon the ribs 

 with yellowish or white. Epidermis solid, dull, not easily rubbed off. 

 Spire conic, more or less depressed, apex acute. Protoconch small, 

 spirally lirate, regularly conoidal. Whorls 5, the last depressed, angu- 

 late at the periphery ; base flat. Suture linear, indistinct. Aperture 

 very oblique, iridescent, lirate. Outer lip convex, angled below, edged 

 with black, then nacreous, and lined with opaque white, the thicken- 

 ing sometimes slightly notched at the place of the periphery. Colu- 

 mella oblique, slightly concave, flat, opaque white, backed by a nacreous 

 band coming from the basal lip and reaching as far as the centre of 

 the umbilical tract. 



Diameter, 13-15 mm. ; height, 9-13 mm. 



Dentition unknown. 



Type (?). 



Hob. From Bay of Islands to Stewart Island ; under stones be- 

 tween tide-marks. Not common, but more abundant in Cook Strait 

 than further north or south. Brought to England by Captain Cook. 



Fossil in the Pliocene. 



8. Monodonta morio, Troschel, 1851. Plate 39, fig. 4. 



Trochus morio, Trosch., in Philippi. Conch. Cab., 142, pi. 24, f. 3. Mono- 

 donta morio, Trosch., Man. Conch. (1), xi, 102. pi. 35, f. 26, 27 ; Suter, 

 P. Mai. S.. ii, 263. M. melaloma, var. guttata, Hutton, P.L.S. N.S.W., 

 ix, 3(37 ; Man. Conch. (1), xi, 105. Trochus (Diloma) porr.ifer, A. Ad. : 

 Watson, Chall. Re])., xv, 67, pi. 4, f. 12, not of Adams. 



Shell semiglobose to conical, solid, black, imperforate. Sculpture 

 consisting of numerous spiral sulci, about 10 on the penultimate 

 whorl, crossed by very fine growth-lines ; the same ornamentation, 

 usually more distinct, upon the base. Colour black, with irregularly 

 scattered white dots. Epidermis dull, easily worn off. Spire low and 

 arched to elevated conoidal, sides strongly convex. Protoconch always 

 eroded, flatly convex, smooth. Whorls about 5, rapidly increasing, 

 slightly depressed below the suture, then convex, the last whorl rounded 

 or subangled at the periphery ; base but little convex. Suture linear, 

 not much impressed. Aperture very oblique, silvery with a greenish 

 lustre, closely lirate. Outer lip convex, sharp, edged with black or 

 blackish-green, followed by a narrow silvery lirate band, and inside 

 this there is in quite adult specimens a broad band of opaque, white. 

 Columbia oblique, nearly straight, nodulous, white, continued as a 

 broad opaque white band inside the pearly edge on the basal lip. 

 Umbilical tract broad, bounded by dark green, and with a pearly 

 impression, the continuation of the band on the lower lip. 



Diameter, 14-19 mm. ; height, 12-20 mm. 



Dentition unknown. 



TypeQ). 



Hob. North and South Islands, as far south as Preservation 

 Inlet ; rather common on rocks and under stones between tide-marks. 



Remark. This species shows a good deal of variation. 



