PELECYPODA 169 



Length i-6 mm. ; height 2-4 mm. (Holotype). 

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



This species is allied to L. insularis, Oliver, 191 5, dredged off Sunday Island, Ker- 

 madec Islands. Both are coarsely ribbed and exceedingly small for their genus. 



Family CRASSATELLITIDAE 

 Genus Cuna, Hedley, 1902 

 Type (original designation) : Cuna concentrica, Hedley, Recent, New South Wales 

 Cuna aupouria, n.sp. (Plate XLVI, figs. 1, 2). 



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

 Prodissoconch small, smooth and globular. Beaks directed backwards. Lunule and 

 escutcheon similar, well developed, long and deep. Hinge massive, but constricted 

 laterally by the deeply excavated lunule and escutcheon. Hinge teeth normal; right 

 valve with two divergent cardinals, left with a rudimentary anterior cardinal and a 

 massive triangular posterior one. The slightly thickened anterior edge acts as a lateral, 

 by fitting into a groove in the opposite valve. Basal margin weakly crenulate within. 

 Interior smooth, adductor scars subequal, distinct. 



Length 2-1 mm.; height 2-3 mm. (Holotype, a right valve). 



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



This species in its smoothness is nearest to otagoensis, Powell (1927, Rec. Cant. Mus., 

 in, pt. 2, p. 120), and although the two species are similar also, in outline, the direction 

 of the beaks is opposite. They differ further in the greatly constricted hinge of the new 

 species. 



Cuna waikukuensis, n.sp. (Plate XLVI, fig. 3). 



Shell small, solid, oblique-trigonal, equivalve, inequilateral, smooth, white. Prodisso- 

 conch small, smooth and globular. In shape the species is very similar to aupouria 

 except that the lunule and escutcheon are very faint, and in consequence there is no 

 constriction of the hinge. The basal margin is weakly crenulated and faintly rayed 

 within, but externally the valves are quite smooth. There are twelve of these sub- 

 obsolete rays. Hinge normal ; right valve with two divergent cardinals, left with a 

 rudimentary anterior cardinal and a massive triangular posterior one. Growth series 

 from young to adult in both species demonstrate that aupouria can always be dis- 

 tinguished by the deeply excavated lunule and escutcheon and massive constricted 

 hinge. In waikukuensis the reverse obtains, the lunule and escutcheon being poorly 

 developed and the hinge moderate and not constricted. 



Length 1-7 mm.; height 1-9 mm. (Holotype, a right valve). 



Habitat: Off Waikuku Beach, St. 930, i-8 miles, 03 5 off North Cape, 29 m. 



Cuna manawatawhia, n.sp. (Plate XLVI, fig. 5). 



Shell small, solid, oblique-trigonal, equivalve, inequilateral, white; sculptured with 

 ten broad flattened radial ribs, with shallow interspaces, of about a third the width of 



