264 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Pecten (Chlamys) bicheoits, n.sp. PL XI, Fig. 31. 



Shell triangularly orbicular, moderately inflated, sub- equilateral, 

 somewhat inequivalve, with rather distant rounded radial ribs ; valves 

 differently coloured, ears very unequal, the anterior large, the posterior 

 very small. Beaks approximate, the prodissoconch small, oval, smooth. 

 Anterior and posterior ends similar, slightly concave above, then forming 

 a half-circle with the basal margin ; right valve slightly more convex 

 than the left, with a rather large triangular anterior ear with four radial 

 costse, crossed by strong and close imbricating growth-lines, a distinct 

 byssal sinus below, and a row of teeth below it on the anterior margin 

 (ctenobium) ; the posterior ear very small, triangular, with a few 

 concentric riblets ; left valve with the anterior ear also triangular, 

 the anterior side straight or lightly sinuous, with about six scaly radiate 

 riblets, the intercostal spaces with one or two fine scaly lines. Sculp- 

 ture consisting of sub-equidistant rounded radial ribs, indenting the 

 margins, their number varying from, sixteen to twenty on each valve ; 

 they are broadly or acutely rounded, sometimes ornamented with 

 scales, more prominent on the left valve ; towards the margin the ribs 

 have often one or several grooves, and in the interstices one to three 

 radial fine riblets may be present ; besides this sculpture there are 

 minute divaricating radial lines (the so-called Ca^nptonectes striation). 

 The concentric sculpture consists of very fine and rather close undu- 

 lating and slightly imbricating layers. Colour of right valve whitish, 

 lightly tinged with pink, rarely yellowish-brown all over ; left valve 

 always much darker coloured, white with red concentric spots and 

 bands, or reddish or yellowish-brown, sometimes mottled with white. 

 Inside shining, white or stained with red, strongly grooved, the 

 margins sharp, dentate, or crenulate. Hinge-line long and straight, 

 the resilifer triangular, not very deep, its margins rather sharply raised. 

 Ligament external, narrow. Length 32, height 36, diam. 10 mm. 



Hab. — A number of valves were found in the stomach of a Blue- 

 Cod {Parapercis coUas, Eorster) caught in Port Pegasus, Stewart Island, 

 and kindly given to me by Captain Bollons. This fish is found in 

 New Zealand waters only : East of Jones Head, in 20 fathoms ; 

 19 miles south of Oamaru, in 40 fathoms ; off Lyttelton, in 100 fathoms 

 (Mr. Edgar E. Waite). 



This species is allied to the Miocene P. Chathamensis, Hutton 

 (Cat. Tert. Moll. jS". Zeal., p. 29), but this form has the ribs more 

 scaly, the scales more distant ; the ribs show no tendency to division 

 towards the margins. The anterior ear of the right valve is not large, 

 has no byssal sinus, and there is of course no ctenobium. The form 

 and size of the shell and the number of ribs are about the same as in 

 the recent species. Type in my collection. 



EXPLANATION OF PLATE XI. 



Fig. 



1. Hissoina zonaia, n.S'p. 4"5xll'5nim. 



2. Skenella Pfefferi, n.s^. -8 x '45 mm. 



3. Trophon (Kalydon) Auclclandicus (Smith) ; operculum. 



4. Id., radula. 



