Shell small, more or less thick, sub-triangular, equivalve,
inequilateral; summits contiguous and turned forward; hinge similar,
formed by a numerous series of very pointed teeth, pectinated and
disposed in a line interrupted under the summit; ligament internal,
short, inserted in a small oblique cavity in each valve; two muscular
impressions; valves more or less pearly within.
Nucula lanceolata.
N. rostrata.
N. pella.
N. Nicobarica.
N. obliqua.
N. margaritacea.
_N. rostrata._ The beaked Nucula.
Species of which the margin is entire.
_N. margaritacea._ The pearly Nucula. Pl. 11, fig. 7.
Species of which the margin is crenated; numerous regular pectinated
teeth; obliquely ovate, trigonal; striæ minute and almost obsolete;
covered with a greenish epidermis; inside silvery, pearl-like.
FAMILY XII.
TRIGONACEA. Two genera.