50 GASTEROPODA. 



233. A. biramOSUS, Quoy, Voy. Astrolabe, iii., p. 378 ; Tonicia 

 corticata, Hutfon, Trans. N.Z. Inst., iv., p. 180. Oval, mantle coria- 

 ceous, with a few scattered long spines, and with a row on each side 

 of nine small tufts, consisting of two diverging spines in each ; valves 

 flatly triangular, depressed ; posterior margins nearly straight, the 

 anterior ones with a small obtuse central point ; lateral areas bounded 

 on either side by a flatly nodulose ridge, the space between being 

 obliquely striated, the stria? running outward and backward ; median 

 areas rugose without either distinct lines or granules. Margin dark 

 brownish black ; valves greyish ; inside white. Generally covered 

 over with white coralline growth and small marine algfe. Length, 2 ; 

 breadth, 1. 



Pitt's Island. 



* 234. A. porphyreticilS, Reeve. Shell somewhat elongately 

 ovate, valves punctured in the middle, verrucosely rough on each side, 

 with a single ridge along the edge of the lateral areas ; anterior 

 terminal valve radiately five-ribbed, posterior small, blunt. Cinereous 

 purple, with a conspicuous yellow spot, dotted with black at the edge, 

 and stained with bright purple in the middle, along the umbonal 

 summit of each valve. {Reeve.} 



235. A. OVatUS, Hutton, Trans. N.Z. Inst., iv., p. 182. Ovate, 

 attenuated in front ; margin spiny, -with nine small bundles along each 

 side ; valves flatly triangular, sub-carinate, posterior valve very narrow, 

 apex recurved ; posterior margins of the anterior plate sloping back- 

 wards into a point, those of the posterior plates nearly straight ; 

 anterior valve with ten, and lateral areas with two on each side, 

 radiating nodulose ridges ; median areas with slightly waved longitu- 

 dinal ridges ; dorsal line smooth. Mantle pale reddish brown ; spines 

 white ; valves greenish white ; yellowish on the dorsal line. Length, 

 - 6 ; breadth, '5. 



236. A. hookeri, Gray, Dieff. N.Z.,u.,p. 262. Oblong; mantle 

 spiny, with nine large radiating tufts of spines on each side ; valves 

 flatly triangular, sub-carinate ; posterior margins slightly convex, with 

 an obtuse central point ; terminal and lateral areas granulose ; median 

 areas smooth ; lateral areas very large. Mantle brown ; spines pale 

 green ; valves generally greyish black, more or less varied with 

 yellowish ; often yellowish or reddish on the dorsal line ; occasionally 

 greenish. Length, 1 ; breadth, - 4. 



Not uncommon on stones below low watermark. 



KATHARINA. 



Valves partly hidden on each side by an expansion of the mantle, 

 sides smooth ; uncovered portions of the valves as broad as long. 

 West Coast of South America. 



237. K. Violacea, Quo//, Toy. Astrolabe, iii., p. 403. Elongated 

 oval ; margin smooth ; valves rounded, depressed ; posterior margins 

 waved ; anterior valve grauulose, six-sided, separated by flat nodulose 

 lines ; posterior valve small, rounded, granulose ; lateral areas small 



