996 PELECYPODA. [E ulamellibranchia. 



line very distinct, distant from the margin, the sinus free, horizontal, 

 Qval-linguiform, rounded in front. 



Length, 57 mm. ; height, 41 mm. ; diameter, 27-5 mm. 



Type in the Mus. Hist. Nat., Paris. 



Hob. - - Throughout New Zealand, common. Auckland and 

 Campbell Islands. 



Remarks. Specimens from the Auckland Islands are brown, very 

 large and solid. 



Maori. Hakari (teste Hutton). 



Fossil. Miocene and Pliocene. 



Subgen. 2. PROTOTHACA, Ball, 1902. 



Protothaca, Ball, Proc. U.S. Nat. Mus., xxvi, 1902, 304 ; Trans. Wagn. Free 

 Inst., iii, pt. 6, 1326. Type : Venus thaca, Molina. 



Shell ovate, moderately convex ; coloration usually whitish or 

 dull ; surface not polished, reticulately sculptured, the radials usually 

 stronger ; sculpture more or less distinctly divided into 3 areas, the 

 middle of the valves being chiefly radial, the anterior radial and 

 scabrous, the posterior irregularly concentric ; the lunule is sharply 

 circumscribed, also the escutcheon of the left valve ; the right valve 

 in the type has no corresponding portion of the escutcheon, and the 

 margin somewhat overlaps that of the left valve, but does not conceal 

 the ligament ; the middle cardinals are usually grooved or bifid ; the 

 pallial sinus of moderate size, nearly horizontal, free below and 

 pointed in front ; the inner margins are sharply crenulated. 



The siphons are short, united, and only the incurrent orifice is 

 papillose ; the foot is hatchet-shaped and not byssiferous. (Ball.) 



Distribution. West coast of Soiith America, Japan, and New 

 Zealand. 



3. Paphia costata, Quoy and Gaimard, 1835. Plate 61, fig. 7. 



Venus costata, Q. & G., Voy. Astrol., iii, 1835, 521, pi. 84, f. 1, 2 ; Crit. List, 

 45 ; Hutton, P.L.S. N.S.W., ix, 522. Chione costata, Q. & G., C.M.M., 

 70 ; J. de Conch., xxvi, 49 ; M.N.Z.M., 148 ; Index, 89. Venus crassi- 

 costa, Quoy : Hanley, Cat. Rec. Biv. Shells, 118, pi. 16, f. 39 ; Conch. 

 Icon., xiv, f. 42. Tapes crassicosta, Quoy, Thes. Conch., ii, f. 93. 



Shell moderately large, transversely ovate, inequilateral, rather 

 thick, yellowish- white, with broad radial ribs and concentric grooves. 

 Beaks contiguous, not much raised, inflated, sharply pointed, incurved 

 and directed forwards. Anterior end short, rounded, the dorsal 

 margin curved and rapidly descending ; posterior end broadly sub- 

 truncated, the dorsal margin straight, slowly descending ; ventral 

 margin very little rounded. Lunule distinctly circumscribed, lanceo- 

 late, obliquely striated. Escutcheon indistinct. Sculpture consisting 

 of broad, flattish radial ribs, much broader at the posterior end ; 

 crossed by concentric stride, which are faint on the middle part, 

 numerous and lamellate anteriorly, and distant posteriorly. Colour 



