Diplodontu.} PELECYFODA. 917 



in 40 fathoms ; twenty-four miles south-east of Long Point, in 120 

 fathoms (E. E. Waite) ; Bounty Islands, in 50 fathoms (Captain 

 Bollons). Also Tasmania and Australia. The type is from King 

 George Sound, Western Australia. 

 Fossil in the Pliocene. 



2. Diplodonta striata, Button, 1878. Plate 63, fig. <i. 



Lucina novce-zelandice, Reeve, Conch. Icon., vi, 1850, f. 14. Mysia novce- 

 zelandice, Reeve : Hutton, C.M.M., 75. Diplodonta novoe-zelandice, 

 Reeve, Grit. List, 46 ; not of Gray, 1835. D. striata, Hutton, J. de 

 Conch., xxvi, 1878, 51 ; M.N.Z.M., 156 ; Index, 92. Mysia striata, 

 Hutt., P.L.S. N.S.W., ix, 525. 



Shell somewhat globose, inequilateral, thin, irregularly concen- 

 trically ridged. Beaks slightly raised, swollen, approximate, curved 

 inward and forward, pointed. Dorsal margins almost horizontal, 

 lightly convex, the others circular in outline. Sculpture consisting of 

 rather irregular rlattish concentric ridges, lamellate near the margins. 

 Epidermis thin, light brown. Colour whitish to very light brown. 

 Interior white, not shining. Margins thin and sharp. Hinge-line 

 straight, narrow ; right valve with a small triangular anterior and a 

 broader sulcate posterior cardinal tooth ; left valve with a broad 

 bifid anterior and small lamellar posterior cardinal tooth. Ligament 

 rather short, high, exterior. Adductor-scars subequal, oblong, near 

 the margin. Pallial line simple- 

 Diameter-- Ant.-post., 15mm.; dorso-ventral, 14 mm. : thick- 

 ness, 11 mm. 



Type in the British Museum. 



liab. New Zealand (Cuming) ; Kapiti Island and Titahi Bay, 

 Cook Strait ; Auckland Harbour ; Banks Peninsula (Iredale) ; Chat- 

 ham Islands. 



On mud-banks and in rock-fissures at and below low-water mark. 



3. Diplodonta zelandica, Gray, 1835. Plate 63, tig. 10. 



Lucina zelandica, Gray : Yate, N.Z., 309 ; Dieff. N.Z., 256. Mi/sia zealandica, 

 Gray, C.M.M., 75. Hutton, P.L.S. N.S.W., ix, 525. Diplodonta zelandica, 

 Gray : Hutton, J. de Conch., xxvi, 51 ; M.N.Z.M., 156 ; Smith, Ereb. & 

 Ter., ii, 1874, 6, pi. 3, f. 8 ; Index, 92 ; Gatliff, P.R.S. Vic., xx (n.s.), 36. 

 Lucina inculla, Gould, P. Bost. S.N.H., iii, 1850, 255 ; U.S. Expl. Exp., 

 xii, 413, atlas f. 524 ; Grit. List, 46. Diplodonta tasmanica, T.-Woods 

 P.R.S. Tas., 1876 (1877), 158 ; Tate and May, P.L.S. N.S.W., 1901, 432 

 pi. 27, f. 102 ; Hedley, op. cit., 1904, 196. 



Shell small, fairly solid, lenticular, subequilateral, nearly circular 

 in outline, valves moderately convex, whitish, with concentric growth- 

 lines. Beaks slightly elevated, rather compressed, acutely triangular, 

 incurved, a slight depression in front of them rendering the anterior 

 half a little less elevated than the posterior. Anterior end somewhat 

 acutely rounded ; posterior and basal margins circularly rounded, 

 most depending portion a little behind the middle. Sculpture con- 

 sisting of fine concentric growth-lines. Epidermis thin, smooth, li"ht 



