146 VENERIDA. 
M. lata, Deshayes; Reeve, Conch. Ic., f. 4. Shell triangularly ovate, 
broad, compressed, concentrically densely irregularly striated, striae more 
grooved at the sides; posterior side rounded, anterior much shorter, 
angularly truncated ; umbones rather flattened ; whitish, covered with a 
pale yellow horny epidermis (Reeve). 
Dunedin. 
M. spissa, Reeve, Conch. Lc., f- 18. Shell triangularly oblong, 
thick; anteriorly rather sharply angled and truncated ;_ posteriorly 
rounded ; compressed at the umbones ; posterior area rather broad, 
sub-concave ; light fuscous white, irregularly striated (Reeve.) 
Abundant. Chatham Islands. Auckland to Dunedin, more com- 
mon in the south. 
The Natives call this shell ‘‘ tuatua.” 
This is probably the same as JZ. sub-triangulata, Gray, Ann. Phil. 
(see Dieff., N.Z., ii., p. 252,) of which I have not been able to finda 
description. It is not the same as JZ. cuneata, Lam., which is found in 
South Australia. 
S2b- Order— Veneracea. 
Siphons moderate ; mantle wide, open in front ; foot large, pointed ; 
gills four. 
FAMILY--VENERID. 
Labial palps small, triangular, acute. Mantle with a somewhat large 
pedal opening ; siphons short, unequal, united for the greater part of 
their length ; gills large, sub-quadrangular, united behind. Foot large, 
compressed, linguiform, sometimes furnished with a byssal groove. 
Shell regular, free, or perforating, closed or somewhat gaping. Hinge 
usually composed of three diverging primary or cardinal teeth in each 
valve ; ligament external, marginal. Muscular inpressions smooth, 
oval ; pallial sine sinuated. 
Sub-Family— Venerine. 
Siphons free at their extremities. Foot lanceolate, without a_byssal 
groove. Shell ovate, sub-trigonal ; hinge with the cardinal teeth trian- 
gular, and with an anterior lateral tooth. 
Genus, VENUS—Linneus. 
Mantle margins fringed or furbelowed ; siphons unequal, separate, 
diverging, the branchial with a double row of cirri, the inner one long 
and simple, the outer shorter, furcate or stellate ; anal siphon conical, 
crowned with short cirri. Shell oval, thick, inequilateral, swollen ; hinge 
with three cardinal teeth, simple or bifid, in each valve, and a smal! 
anterior lateral tooth ; transversely grooved or lamellate, margin finely 
crenulated ; pallial line short and sinuous, always oblique. 
