Astrcea.] GASTROPODA. 167 



excavated in the middle, then flatly convex, and with a circular de- 

 pression inside the circle of spines. Suture rendered zigzag by the 

 prominent spines. Aperture transversely oval, pearly within. Outer 

 lip convex, sharp, channelled, and much produced at the junction 

 with the slightly convex and denticulate lower lip. Columella con- 

 cave above, oblique and straight below, white and smooth. Inner lip 

 slightly dilated, and impinging upon the umbilicus ; parietal wall 

 strongly iridescent, a thin glaze uniting the two margins. Umbilicus 

 wide, deep, perspective. Operculum oval, with excentric nucleus ; 

 outside smooth, obsoletely unicostate. 



Diameter, 100-120 mm. ; height, 50-60 mm. 



Dentition. Hogg, Trans. Microsc. Soc., 1866, pi. 11, f. 46. 



Hob. From the Bay of Islands to Stewart Island ; Cloudy Bay 

 (Forster) ; Tasman Bay (Q. G.) ; Auckland (Frauenfeld) ; Chatham 

 Islands. From low-water mark to about 20 fathoms. Found also at 

 Lord Howe Island. Brought to England by Captain Cook. 



Fossil in the Pliocene. 



Subgen. 2. COOKIA, Lesson, 1832. 



CooJcia, Lesson, Illustr. Zool., 1832, pi. 15. Only species : A. sulcata, Mart. 

 Median tooth of radula with a long basal plate and short body ; 

 it bears no cusp, and has small supporting-wings. 



Shell large, conical, imperf orate ; periphery rounded or keeled ; 

 base concave ; umbilical tract concave, smooth ; operculum ovate, 

 narrowed toward the distal extremity, nucleus subterminal, outside 

 with 2 convex smooth ribs. 



2. Astrasa sulcata, Martyn, 1784. Plate 41, fig. 2. 



Trochus sulcatus, Mart., Un. Couch., i, f. 35, not of 1769. AstraUum 

 xuhatum, Mart., Man. Conch. (1), x, 242, pi. 64, f. 55. Trochus Cooki, 

 imelin, Syst. Nat., ed. xiii, 1790, 3582. Cookia nobilis, Lesson, Illustr. 

 Zool., 1832, pi. 15. Pachypoma (Cookia) Cooki, Chenu, Man. Conch., i, 

 351, f. 2581. 



Shell large, conic, imperforate, rather thin, with oblique sub- 

 tuberculose folds. Sculpture consisting of close lamellose growth- 

 striae and obliquely descending subtuberculose folds, which are directed 

 forward ; base with 5 to 6 slightly nodulous spiral ribs, crossed by 

 close growth-lines. Colour purplish-grey or brown, centre of base 

 fawn-coloured. Spire conoidal, more or less elevated, higher than 

 the aperture. Protoconch small, depressed convex, of 2 smooth whorls. 

 Whorls 7, well rounded, periphery convex ; base flattened, deeply 

 concave in the centre. Suture deeply impressed. Aperture trans- 

 versely oval, very oblique, pearly and corrugated within. Outer lip 

 strongly convex, denticulate, edged with brown ; basal lip nearly 

 straight, with an interior white callus. Columella arcuate above, 

 straightened and very oblique below, thin, white above, pearly below. 



