OCR Text |
Show 1881.] THE SURVEY OF H.M.S. 'ALERT.' 39 acute. Lunule narrow. Ligamental area lanceolate, twice as as the ligament. Hinge with two teeth in each valve, whereof the anterior in the right valve and the posterior in the left are bifid. Anterior scar narrow, elongate, running some way from the upper front margin downwards; posterior scar broader, roundly ovate. Pallial line simple, joining the front scar at its upper end. Interior of valves exhibiting an irregular corrugation or punctation. Width 9| millims., length 8, thickness 3|. Hab. Station 5. This pretty species is very different from most others of the genus in being sculptured with raised lamellae. MACTRA (MULINIA) LEVICARDO, sp. n. (Plate V. figs. 2-2 b.) Shell ovate, subtrigonal, inequilateral, livid from the centre of the valves to the umbones, elsewhere white, covered with a greyish-olive epidermis. Valves moderately convex, with a faint ridge or angulation from the umbo to the hinder extremity, which is very slightly angulated, and with a shallow depression nearer the dorsal line, marked by a wrinkling of the epidermis. Interior white. The sculpture consists of concentric stria?, very fine near the apex, and rather coarse towards the outer margin. Umbones small, acute, not far apart, situated a little anteriorly. Hinge remarkable on account of the small size of the cartilage-pit; and the whole construction of the hinge is slight. Pallial sinus rather deep, but not acute. Diam. 56 millims., length 44, thickness 22. Hub. Cockle Cove, 7 fathoms., mud. M. edulis of King appears to be the nearest ally of this species, which differs especially in having a much smaller cartilage-pit, a less deep pallial sinus. The form also is more transverse and the dorsal slopes less arcuate, thus giving a more triangular appearance to the outline. NUCULA PISUM, var. Hab. Station 2. A single specimen of this species is of a rather narrower and more triangular form than normal examples. LEDA LUGUBRIS, A. Adams. Hab. Station 2; and Wolsey anchorage, 17 fathoms, mud and gravel. MALLETIA MAGELLANICA, Smith. (Plate V. figs. 3, 3 a.) Hab. Station 3, Mayne Harbour, 9 fathoms, greenish mud; and Cockle Cove, 2-32 fathoms, mud. The typical specimens of this species were collected somewhat south of the above localities at Otter Island. One of those just received is a very fine example, being 38 millims. broad, with a length of 20 ; and the beaked end is remarkably acute. |