Pecten.] PELECYPODA. 879 



the interstices with iione or 1 to 3 much finer ribs ; there is a very 

 great variability in the arrangement of the ribs, and occasionally it- 

 is similar to that of P. aspcrrinius ; on the other hand, specimens 

 occur which show only the strong prominent ribs, the interstices with- 

 out or only an occasional finer riblet. Otherwise this subspecies does 

 not differ from the species. 



Type in the British Museum. 



Hab. South Island : Nelson ; off Jones Head, in 20 fathoms ; 

 south of Oamaru, in 40 fathoms (E. R. Waite). Stewart Island (C. 

 Traill). Chatham Islands. 



Sect. 2. PALLIUM, Schumacher, 1817. 

 Pallium, Schumachei', Essai Nouv. Syst., 1817. Type : Pecten plica, Lam. 



Shell with the disc high and narrow above, ears small ; valves 

 moderately inflated, nearly similar, the basal margin in the adult 

 contracted, so that the edges meet each other nearly vertically ; ribs 

 few, large, widening distally, entire ; surface radiately imbricately 

 striate, frequently with Camytonectes striation, and imbricate external 

 layer ; the cardinal crura usually well developed, often irregular. 



6. Pecten convexus, Quoy and Gaimard, 1835. Plate 56, figs. 8, a. 



Pecten convexus, Q. & G., Voy. Astrol., iii, 1835, 443, pi. 76, f. 1-3 ; Hutton, 

 J. de Conch., xxvi, 55 ; P.L.S. N.S.W., ix, 532 ; Index, 93. P. roseo- 

 punctatus, Reeve, Conch. Icon., viii, 1852, f. 84. P. (Dentipecten) velli- 

 catus, Hutton, C.M.M., 82 ; M.N.Z.M., 171. 



Shell slightly inequivalve, the right valve generally more inflated, 

 the anterior ears somewhat larger, rounded, solid, with 4 to 5 broadly 

 convex radiate ribs and very numerous finer ones, white spotted with 

 pink, or reddish to purplish. Beaks minute, approximate, the pro- 

 dissoconch smooth and sharply pointed. Ears unequal, the anterior 

 ones larger ; they are radially strongly ribbed, and the ribs crossed 

 by numerous fine concentric strise, some of which are squamose ; right 

 anterior auricle with very narrow byssal fissure, the opposite margin 

 of the disc with a ctenolium. Discs triangular above, distinctly 

 shouldered at the ears, rounded below, anterior end narrowly convex, 

 posterior end a little more produced than the anterior, angularly 

 rounded. Sculpture of discs consisting of 4 or 5 broad rounded radiate 

 ribs and numerous small unequal and inequidistant radiate ribs, 

 crossed by fine wavy concentric growth-lamellae. Colour white spotted 

 with pink or flesh-red, the right valve always of a paler colour than 

 the left, sometimes reddish, purplish, or white with the large ribs only 

 pink-coloured. Interior pinkish or white, shining, deeply grooved. 

 Margins undulating, finely crenulate. Hinge-plate moderately broad, 

 with rather indistinct cardinal crura. Resilifer small, triangular ; 

 external ligament narrow, extending the whole length of the hinge- 

 line. Adductor-scar hardly impressed, irregularly rounded, subcentral, 

 nearer the posterior end. Pallial line simple. 



