“Cryptodon falklandicus, n. sp. (Pl. XIV. figs. 3-3a).
Testa rotundata, mediocriter convexa, paulo inæquilateralis, alba, cretacea, epidermide tenui flavescente induta, concentric striata. Valvæ tenues, sulco postico lato radiant haud profundo aratæ. Margo ligamenti leviter arcuatus, anticus declivis, rectiusculus. Latus anticum ad extremitatem rotundatim subangulatum, posticum breviter truncatum. Pagina interna alba, purum nitida, plus minusve rugosa. Cicatrix antice magna, elongata, irregularis, posterior minor, brevior.
This species is a trifle longer than high, roundish, moderately convex, thin, white, of a chalky appearance, and covered more or less with a thin yellowish epidermis. It is somewhat inequilateral, the beaks being situated a little in advance of the centre, and striated rather roughly by the lines of growth. The valves exhibit a broadish shallow depression down the posterior side, which produces a short truncated extremity to the margin. There is also a faint depression on the opposite side, marking off an elongate cordate lunular space. The posterior or ligamental portion of the dorsal margin is a little curved and less oblique than the anterior, which is straightish, and joins the upcurving ventral outline almost in a rounded angle. The hinge-line is thickened slightly to support the strongish ligament, also just in front of the apices. The interior of the valve is opaque-white, hardly at all glossy, and rather rough through being somewhat punctuate and irregularly striate. The anterior muscular impression is very long, with a jagged outline, and falls partly within the subpunctate pallial line. The hinder scar is much smaller, and somewhat coarsely striated.
Length 15 ½ mm., height 14 ½, diameter 8.
Habitat. -- Station 316, off the Falkland Islands, in 3 to 5 fathoms; mud.
Lucina plicifera (A. Adams), from Borneo, is somewhat like this species in form, having a radiating depression down each side, but is more strongly concentrically ridged, and has a single anterior lateral tooth in each valve, whilst Cryptodon falklandicus is totally edentate.”
(Smith, 1885: 190-191)
