Leda.] PELECYPODA. 835 



similar ; fossette containing the resilium internal, placed below the 

 beaks ; pallial line feebly sinuous ; internal layer porcellanous. 



Distribution. All seas, coralline and abyssal zones 2,800 metres 

 (" Belgica "), 1,675 fathoms (" Challenger "). 



Fossil in the Tertiary of New Zealand and Australia. 



KEY TO SPECIES. 



A. Shell always strongly concentrically sulcate ; interstices smooth 



or with fine growth-lines. Height to length, 1:1-7.. . . bettula. 



B. Shell from smooth to concentrically sulcate, with a microscopic 



punctate pattern. Height to length, 1:2 . . . . fastidiosn. 



1. Leda bellula, A. Adams, 1856. Plate 63, figs. 2, a. 



Leda bellula, A. Ad., P.Z.S., 1856, 49 ; Hanley, Thes. Conch., iii, 1860, 122, 

 pi. 228, f. 74 ; Hedley, T.N.Z.I., xxxviii, 1905 (1906), 70 ; Suter, T.N.Z.I., 

 xl, 353. L. australis (Q. & G.), Button, C.M.M., 81 ; not of Quoy and 

 Gaimard. L. concinna, A. Adams, Grit. List, 49 ; Hut ton, J. de Conch., 

 1878, 54 ; M.N.Z.M., 165 ; P.L.S. N.S.W., ix, 529 ; Index, 95 ; not of 

 A. Adams. 



Shell rather small, solid, elongately oval, with a sharp posterior 

 beak, equivalve, inequilateral, concentrically sharply costate, colour 

 light brown. Beaks at about the anterior third, approximate, rounded, 

 slightly directed backward. Anterior end shorter than the posterior, 

 dorsal margin slowly descending, thence regularly convex toward the 

 arched basal margin ; posterior end longer, with a sharp beak, the dorsal 

 margin slightly descending, concave. Lunule indistinct, bordered by 

 very faint ridges. Escutcheon very prominent, lanceolate, very finely 

 longitudinally striate, limited by creuated ridges, the posterior dorsal 

 margins of the valves forming a sharp median keel. Sculpture con- 

 sisting of subequidistant concentric sharp riblets, close together at the 

 umbones, but further down the interspaces are broader than the riblets 

 and contain a few growth-lines. Epidermis thin, not shining. Colour 

 light brown. Interior bluish-white, porcellanous ; margins smooth. 

 Hinge-line angulate ; resilium very small, triangular ; teeth numerous, 

 V-shaped, the anterior series very little shorter, with about 15 teeth ; 

 the posterior with 15 to 16 teeth. Adductor -scars deeply impressed, 

 the posterior scar larger than the anterior, which is transversely striated. 

 Pallial line verv little sinuated. 



it 



Length, 10 mm. ; height, 5-2 mm. ; diameter, 4 rnm. 



Type in the British Museum. 



Hob. Of? Great Barrier Island, in 110 fathoms ; five miles south 

 of Cuvier Island, in 38 fathoms (Captain Bollons) ; near Channel 

 Island, Hauraki Gulf, in 25 fathoms ; Cook Strait ; Dusky Sound, 

 in 30 fathoms ; Stewart Island, in 18 fathoms. 



Remarks. Hutton followed von Martens in identifying this species 

 with L. concinna. I sent a specimen from Stewart Island to the 

 British Museum for comparison with the type of L. bellula. Mr. E. A. 



27* 



