Pecten.] PELECYPODA. 877 



interspaces with a still much finer riblet, all being distantly squamose ; 

 right valve with 10 ribs, which are unequal, flattened, grooved and 

 formed by the union of squamose riblets, the interspaces much narrower 

 than the tibs. Colour of the left valve purplish-brown, and reddish- 

 brown on the principal ribs ; on the right valve the ribs are whitish or 

 yellowish-red, the interstices darker. Interior polished, white, rayed 

 with brown or purple. Margins denticulate. Hinge with distinct 

 cardinal and anterior auricular crura. Resilifer narrowly triangular ; 

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



Diameter Ant. -post., 18 mm. ; dorso-ventral, 19 mm. : thickness, 

 7 mm. 



Type in the British Museum. 



Hob. New Zealand ; collected by Dr. Gall, of H.M.S. " Acheron ' ! 

 (type) : Cape Maria van Diemen ; Hauraki Grulf ; Nelson ; Bay of 

 Islands ; Chatham Islands : on rocks near low-water mark. 



Remarks. This species is more or less closely related to P. bifrons, 

 Lamarck ; P. lividus, Lamarck ; and P. aktinos, Petterd. 



4. Pecten radiatus, Hutton, 1873. Plate 56, fig. 9. 



Pecten radiatus, Hutton, C.M.M., 82 ; J. de Conch., xxvi, 55 ; M.N.Z.M., 

 171 ; P.L.S. N.S.W., ix, 532 ; Index, 93 ; Hedley, P.L.S. N.S.W., 

 xxxiii, 1908, 472, pi. 10, f. 28 ; Bavay, Bull. Mus. Hist. Nat,, Paris. 

 r.'-09, pt. 5, 277-8'X pi. 4. 



Shell of medium size, orbicular, compressed, equi valve, the ears 

 very unequal, thin, finely radially ribbed. Beaks small, sharply 

 pointed, approximate. Anterior ears ^irge. triangular, that of the 

 right valve with a small rounded byssal sinus ; posterior ears much 

 smaller, higher, narrowly triangular. Disc? with the dorsal margins 

 descending, slightly concave, the anterior, posterior, and basal margins 

 regularly rounded ; right valve with a ctenolium. Sculpture : The 

 right anterior ear with the upper area radially ribbed, ribs about 7, 

 crossed by imbricating lamellae which extend over the byssal area ; 

 the right and left posterior ears with about 10 subequal oblique radial 

 riblets, crossed by sharp upright vertical lamella? ; the left anterior 

 ear with about 10 scabrous radial riblets ; discs with numerous fine 

 radial ribs, about 20 to 24 near the beaks, increasing to about 80 at 

 the margin ; these ribs are either subequal and equidistant, or they 

 are grouped into about 24 ribs, each consisting of a stronger median 

 rib which extends to the umbones, and 2 to 4 smaller, shorter riblets 

 in the interspaces ; distinct Camptonectes striation is present ; there 

 are dense fine and wavy concentric growth-lines, produced into fine 

 scales on the lower half of the riblets. Colour very variable red, 

 lemon - colour, ochraceous, reddish, or brownish - purple. Interior 

 shining, radially grooved, of the same colour as the outside. Mar- 

 gins thin and sharp, denticulate. Hinge with distinct cardinal and 

 auricular crura. Resilifer triangular ; the external small ligament 

 extending the whole length of the hinge-line. Adductor-scar large, 

 roundish, posterior. Pallial line simple. 



