Malletia australis, Quoy and Gaimard.
Solenella australis, Quoy and Gaimard, Voy. “Astrolabe,” Zool., iii, 1835, p. 471, pl. 78, f. 5–10.
A single valve.
Bathyarca cybaea, n. sp. Plate I, figs. 3, 4.
Shell small, oblong, short and inflated, inequivalve, a little inequilateral without impressed ray, posteriorly and anteriorly rounded, sinuate beneath the beak. Colour white, probably bleached. Sculpture finely reticulate. A series of delicate subequal evenly spaced riblets radiate from the umbo to the margin; as growth proceeds new riblets are intercalated till about fifty reach the margin. The radii are broken into short lengths by concentric growth-lines which produce minute prickles at the point of intersection. Beak much inrolled, at a third of the length of the shell. Ligamental area narrow
Hinge-plate edentulous under the beaks, posteriorly with four nearly horizontal, anteriorly with four highly inclined small teeth. Interior rayed by imprint of external sculpture. Margin finely crenulate within except at byssal gape. Length, 3 mm.; height, 2·15 mm.; depth of single valve, 1 mm.
This species, represented by numerous specimens, is nearest allied to the Australian B. perversidens, from which it differs by the less development of the posterior side.