PETRICOLID. 153 
nally frequently and finely lirate; lire at the posterior side deeply 
angled or divaricate, and joining one another ; anterior side very short, 
posterior slightly broader, obliquely truncated ; superior and inferior 
margins parallel; umbones oblique, swollen, approximate ; interior of 
valves reddish-saffron, towards the periphery violet; pallial sinus 
narrow, deep, apex acuminate, ascending (Deshayes.) 
New Zealand. (Cuming.) 
FAMILY—PETRICOLID. 
Shell ovate, thin, swollen, inequilateral, equivalve, gaping at both 
ends ; teeth two in each valve, unequal, the larger bifid ; pallial line 
remote from the margin in front, broad and deeply sinuated behind. 
Genus, PETRICOLA—Lamark. 
Ovate, transverse, thin, hinge broad. 
P. serrata, Deshayes, Cat. Veneride, Brit. Mus., p. 212; Sowerby, 
in Reeve’s Conch. Lc., f- 1. Elongate, very narrow, cylindrical ; dirty 
reddish ; extremities obtuse, gaping ; longitudinally ridged, the ridges 
larger and denticulated at the anterior end, thin in the middle, and 
more numerous and undulating at the posterior end; valves thin ; 
interior dirty white ; pallial sinus elongate ; apex obtuse ; base broader 
(Deshayes. ) 
New Zealand. (Cuming.) 
SECTION—INTEGROPALLIATA. 
Pallial sinus small ornone. Shell regular, rarely gaping ventrally, 
with hinge teeth. 
Sub-Order— Cyprinacea. ‘ 
Gills, two on each side, unequal ; foot large. 
FAMILY—CARDIID. 
Palpi slender, acuminate; mantle freely open in front; siphons 
distinct, but very short, and nearly sessile, their bases and sides fur- 
nished with tentacular filaments ; gills two on each side, thick, united 
together behind the body. Foot very long and geniculate. Shell 
cordate, swollen, equivalve ; cardinal teeth irregular ; laterals remote, or 
none ; pallial line simple ; ligament external ; generally radiately ribbed, 
rarely smooth ; posterior differently sculptured to the front and sides. 
Genus, CARDIUM—Linneus. 
Ventricose ; umbones prominent ; margins crenulated ; pallial line 
more or less sinuated ; umbones sub-central. 
C. striatulum, Sowerby ; Reeve, Conch. Ic., f- 60; C. pulchel- 
lum, Gray, Dieff. N.Z., ii., p. 252, nec Reeve. Sub-cordate, rather ven- 
tricose, thin, rosy-white varied with red; umbones generally white ; 
