MACTRIDA. 139 
rather attenuately rounded; umbones very small, close; lunule and 
area very natrow, indistinct, plicately striated (Reeve.) 
Much like a Ze//zna. 
Stewart Island. 
M. equilateralis, Deshayes, P.Z.S., 1853, p. 17; Reeve, Conch. 
Ic., f. 14; Voy. Erebus and Terror, pl. 2, f- 10. Trigonal, nearly as 
high as long, solid, longitudinally striated ; lunule smooth ; anterior end 
subangulated, slightly flattened above ; posterior angled and flattened 
above; white; umbones tipped with purplish; interior yellowish, 
sometimes purplish in the upper part.” 
Pierehi 1°75; leneth; 2°25. 
Common. Auckland to Dunedin. 
M. donaciformis, Gray, Beecher’s Voy. Moll. p. 154; Reeve, 
Conch. Ic., f- 62. Shell ovately triangular, inequilateral, swollen, semi- 
cordate ; umbones sharp, opposite, distant, transversely very finely 
striated ; white, beneath a fulvous epidermis, anteriorly obtuse, pos- 
teriorly broadly flat and angled, accuminated at the extremity (Reeve.) 
New Zealand. (Cuming.) 
Sub-Family—Lutraritne. 
Mantle lobes generally united. Shell oblong or elongate, gaping 
behind ; lateral teeth very small, rudimentary, often obsolete, especially 
in the adult shell. 
Genus, STANDELLA—Gray. 
Shell ovate, hinder slope more or less keeled; hinge with the 
lateral teeth short, smooth, the anterior oblique ; lhgament sub-external, 
marginal, not separated from the cartilage. 
S. ovata, Gray, Dief. N.Z, ii, p..251 3) Reeve, Conch. Ic. 
(Mactra,) f. 30; M. rudts, Hution, Cat. Tert., Moll. N.Z., p. 19; M. 
deluta, Gould, U.S. Ex. Ep.  Ovate, ventricose, inequilateral, thin, 
slightly concentrically wrinkled; rounded in front, rather attenuated 
and produced behind; white, covered with a thin pale brown periostraca, 
much produced beyond the edge behind; inside yellow; lateral teeth 
short, very high and sub-triangular (Gray.) 
Auckland to Dunedin. 
S. elongata, Quoy and Gaimard, lc, i., p. 518, pl. 83, f. 1.2, 
nec., Reeve; M. inflata, Hutton, Cat. Tert., Moll. N.Z., p. 18. Oval, 
anterior side shorter, rounded, its dorsal margin rather concave ; pos- 
terior side rounded, its dorsal margin convex ; umbones rather inflated, 
incurved ; smooth or lightly concentrically striated. 
Height, 2°3 ; length, 3. 
S. notata, Hutton, C.M.M., p. 64; M. elongata, Reeve, Conch. 
Ic., f: 43, nec., Q. & G. Thick, solid, concentrically striated round the 
margin ; lunule and area plicately rugose, rest smooth ; anterior end 
