Genus Corbula Lamarck, 1801.
Type: C. sulcata Lamk.
Corbula howesi n. sp. (Figs. 79, 80, 82.)
Closely allied to C. zelandica Q. and G., but differing in the anterior dorsal margin being straighter and more steeply inclined producing a narrowly-rounded anterior end. The shell is more heavily built than the Recent species, but the sculpture is practically the same, there being considerable variations in the strength of the concentric ridges. The hinge-plate is much stronger in C. howesi, and in the right valve the conical tooth is larger but does not project below the hinge-plate as in C. zelandica. In front of the tooth in C. zelandica the hinge-plate narrows and almost disappears, but in C. howesi it is quite wide and continues round towards the anterior adductor. The tooth of C. zelandica is generally well inclined but that of C. howesi is more vertical. There are corresponding differences between the left valves. Viewed from above the notch for the
reception of the cardinal tooth is narrower in C. howesi and the denticle behind the ligamental area is not so distant.
Height 8.5 mm.; length 14 mm.
Localities: Flower-pot; Whenuataru Peninsula.
Corbula tophina n. sp. (Fig. 78.)
Shell small, moderately inflated, valves slightly unequal; beaks broad, about anterior third; anterior end narrowly convex; posterior end broadly, obliquely truncated, an angular ridge extends from the umbo to bluntly pointed lower extremity of posterior margin; posterior area concave. Sculpture of weak, rounded, concentric ridges with linear interstices, four or even five per mm. Hinge of right valve with strong conical cardinal tooth immediately below umbo, and very large ligamental gap behind it.
Height 6.75 mm.; length 9 mm.; thickness (right valve) 3 mm.
Locality: Cliffs below Wireless Station, Waitangi.
Remarks: Not closely related to any New Zealand species.