902 PELECYPODA. \EulamellibrancJiia. 



15 equidistant narrow smooth rounded radiate riblets, the interstices 

 deep and narrower than the costse ; concentric undulating growth- 

 lines are distinct only near the base. Colour white. Interior white, 

 porcellanous, shining. Basal margins crenate. Hinge broad ; the right 

 valve with a stout triangular cardinal tooth, sometimes bifid ; left 

 valve with 2 divergent cardinal teeth, the posterior usually bifid. 

 Resilifer small. Adductor -scars distinct, impressed. Pnllial line simple. 



Length, 2-5 mm. ; height, 3 mm. ; diameter, 1-5 mm. 



Type in the Canterbury Museum, Christchurch. 



Hab.Oft Lyttelton, in 100 fathoms (E. R. Waite). 



2. Cuna delta, Tate and May, 1900. Plate 52, figs. 14, a, b. 



Carditella delta, Tate and May, T.R.S. S.Aust., xxiv, 1900, 102 ; P.L.S. 

 N.S.W., xxvi, 1901, 434, pi. 27, f. 100, 101 ; Hedley, Rec. A.M.. iv, 

 1901, 23, f. o. Cuna delta, T. & M. : Hedley, Mem. A.M., iv, 1902, 31(5 ; 

 Rec. A.M., v, 1904, 87; T.N.Z.I., xxxviii. 1905 (19015), 73; Verco, 

 T.R.S. S.Aust., xxxi, 1907, 109. 



Shell very small, trigonal, rather solid, inequilateral, lightly radially 

 ribbed. Beaks close together, the prodissoconchs small, smooth, 

 conical. Anterior end somewhat produced, dorsal margin descending, 

 straight, convex towards the regularly rounded basal margin ; posterior 

 end distinctly angled below. Lunule distinct, long, and narrow. 

 Escutcheon similar to the lunule. Sculpture consisting of about 10 

 narrow, rounded, distant, and but little raised radiate riblets, very 

 often obsolete, the interstices much broader than the riblets ; con- 

 centric growth-lines distinct, especially towards the base. Colour very 

 light brown. Interior of the same colour, shining. Basal margins 

 slightly crenate. Hinge typical. Resilifer small. Adductor- scars very 

 distinct. Pallial line simple. 



Length, 2-3 mm. ; height, 2-5 mm. ; diameter, 1-4 mm. 



Type in the Tasmanian Museum, Hobart. 



Hob. Off Great Barrier Island, in 110 fathoms ; Cuvier Island, in 

 38 fathoms (Captain Bollons) ; north-east of Wreck Reef, in 50 to 54 

 fathoms (E. R. Waite) ; Foveaux Strait and Stewart Island, in 15 

 fathoms (A. Hamilton) ; Dusky Sound ; near the Snares, in 50 fathoms 

 (Captain Bollons). Also Tasmania and Australia. 



Remarks. The specimens from the Snares are considerably larger 

 than those from the other localities. The type is from Derwent 

 Estuary, Tasmania. 



Fam. CARDITID^E, Ferussac. 



Animal marine ; foot carinated, often byssiferous ; there are no 

 siphons ; the border of the mantle is pierced for the excurrent orifice, 

 while the incurrent orifice may or may not be complete. The gills 

 are coarsely reticular, and usually united behind the foot. In many, 

 if not all, cases the young are developed within the body-cavity of the 

 mother, and retained there until some progress in secreting the nepionic 

 shell has been made, in addition to the completion of the prodissoconch. 



