, 7 o DISCOVERY REPORTS 



the ribs. Prodissoconch small, smooth and globular. Beaks directed forwards. Anterior 

 end the shorter, dorsal slopes straight to the middle, below which is the broad arcuate 

 sweep of the base, which is produced a little posteriorly. Hinge typical. Lunule and 

 escutcheon well defined, bounded by an angular ridge. Interior smooth, external 

 ribbing showing through only at the basal margin, which is rendered slightly sinuose, 

 hardly crenulate. 



Length 2-6 mm.; height 29 mm. (Holotype, a left valve). 



Habitat: Off Three Kings Islands, St. 934, 92 m. 



This species is nearest to C. mayi, Powell, from 10 to 12 fathoms off Wanganui. It 

 combines the sculpture of this species with a shape similar to that of C. compressidens, 

 Powell, from 6 fathoms off Mangonui. 



Cuna gibbosa, n.sp. (Plate XLVI, fig. 4). 



Shell minute, solid, oblique-trigonal, equivalve, inequilateral, smooth, dull white. 

 Prodissoconch small, smooth and globular. Beaks directed forwards and situated near 

 to the anterior end, on account of the high strongly arched posterior dorsal margin, 

 which is subangled at two-thirds the height of the shell. Lunule long and deeply con- 

 cave, escutcheon not prominent owing to the strongly arched posterior slope. Anterior 

 end subangled at about half the height. Ventral margin broadly rounded but obliquely 

 canted forwards. Valve margins smooth. Hinge abnormal owing to the obliquely 

 humped shape of the shell. Left valve with a rudimentary anterior cardinal and a 

 massive elongate posterior cardinal. Right valve not seen but evidently like that of 

 otagoensis, which has a massive anterior obliquely elongate cardinal and a posterior thin 

 lamellate one bordering the dorsal margin. 



Length 2-00 mm. ; height 2-25 mm. ; thickness 07 mm. (Holotype). 



Habitat: Off Three Kings Islands, St. 933, 260 m. 



This species is allied to C. otagoensis, Powell (1927, Rec. Cant. Mns., ill, pt. 2, p. 120), 

 but is more obliquely humped in outline and lacks any trace of radials towards the 

 dorsal margin. It also resembles the Tasmanian C. hamata, Hedley and May (1908, 

 Rec. Austr. Mus., p. 124). 



Family CARDITIDAE 



Genus Pleuromeris, Conrad, 1867 



Type (by monotypy) : Pleuromeris decemcostata, Conrad ( = Cardita tridentata, Say) 



Pleuromeris latiuscula, n.sp. (Plate XLV, fig. 5). 



Shell small, subcircular, equilateral, only moderately convex, pale buff, sculptured 

 with twenty rather indistinct broad radial ribs, having linear interspaces. These are 

 crossed somewhat irregularly by numerous very fine concentric growth lines. Prodisso- 

 conch minute, smooth and globular. Hinge typical ; left valve with two almost equally 

 developed, bluntly triangular, divergent cardinals and an anterior and a posterior lateral ; 



