Trochus.} GASTROPODA. 109 



smooth. Columella oblique, straight, in adult specimens with a few 

 inconspicuous plications above. Umbilicus filled with callus, leaving 

 only a slight pit. 



Diameter, 6 mm. ; height, 5-5 mm. (type). 



Dentition. Hutton, T.N.Z.I., xv, 124, pi. 14, f. M. 



Type in the Otago Museum, Dunedin. 



Hob. Auckland (type) ; Hauraki Gulf (H. S.) ; East Cape ; Lyall 

 Bay ; Taumaki Island, west coast of South Island, in 10 fathoms 

 (Captain Bollons) ; Chatham Islands ; Bay of Islands. 



3. Trochus tiaratus, Quoy and Gaimard, 1834. Plate 39, fig. 2. 



Trochus tiaratus, Q. & G., Voy. Astrol., Zool., iii, 1834. 256, pi. 64, f. 6-11 ; 

 Man. Conch. (1), xi, 42, pi. 12. f. 72-74; Suter, P. Mai. S., ii, 260. 

 Anthora tiarata, Q. & G., M.N.Z.M., 94. Trochus delicatulus, Philippi, 

 Zeitschr. Malak.. 1846, 105. Polydonta elegans, Gray, in Yate's N.Z., 

 1835, 309. 



Shell depressed conical, rather thin, apex acute, with a deep and 

 smooth false umbilicus. Sculpture above consisting of spiral lirae, about 

 5 to 8 on each whorl, cut into close oblique beads, the interstices 

 obliquely finely striate, one or two of the broader ones usually with 

 a central riblet ; base with 8 to 12 spiral beaded cords, stronger 

 and much finer ones usually alternating. Colour whitish, sometimes 

 greyish-green, finely tessejlated with reddish -brown, the tessellations 

 formed by the disintegration of narrow radiating stripes, which are on 

 the base frequently continuous ; colour lemon - yellow when eroded. 

 Spire conical, often depressed, the outlines slightly convex. Proto- 

 conch small, convex, consisting of two smooth whorls. Whorls 5 

 to 5J, nearly planulate, but the upper margin of each whorl pro- 

 minent and projecting beyond the periphery of the preceding ; last 

 whorl carinated or sharply angled at the periphery ; base nearly flat. 

 Suture impressed. Aperture subrhomboidal, smooth within, pearly. 

 Outer lip sharp, convex, margined inside with a narrow white callus ; 

 basal lip straight. Columella oblique, nearly straight, with a dis- 

 tinct fold above, inserted upon the side of the false umbilicus ; um- 

 bilical area white or yellow, smooth, but partly filled by a white 

 callus, not tapering to a point. 



Diameter, 13-5 mm. ; height, 10 mm. Diameter, 19 mm. ; height 

 17 mm. 



Dentition. Hutton, T.N.Z.I., xiv, 165, pi. 7, f. N ; Man. uonch. (i), 

 xi, pi. 50, f. 5 (top fig. on left side, should be 4). 



Type in the Mus. Hist. Nat., Paris. 



Hob. Coasts of the North and South Islands, on rocks near 

 low-water mark ; Chatham Islands, where a much depressed form 

 occurs ; Hauraki Gulf, in 25 fathoms. The type is from Tasmau Bay. 



Fossil in the Pliocene. 



Maori. Mimiti (fide Quoy and Gaimard). 



