126 THE VOYAGE OF H.M.S. CHALLENGER. 



of the radiating costse towards the lunula are thicker than the rest on the central part of 

 the valves, and others just in advance of the dorsal area are much more slender and not 

 granular, being crossed by the concentric ILrse which at this particular part rise into very 

 thin, frill-like lamellae. The dorsal margin descends very obliquely on both sides, is a 

 little arcuate, and near the hinder extremity generally exhibits an indication of a feeble 

 sinuation, which, together with a similar faint incurvation in the lower outline, gives this 

 portion of the shell a somewhat rostrate character. The lunule varies in form, in some 

 examples being lanceolate and in others longish heart-shaped. It is radiately-granulosely 

 ridged, concentrically striated, prominent along the middle, and enclosed by a narrow 

 deep groove. The area is comparatively smooth, without radiating Urpe, merely sculptured 

 with very fine striae of growth, and generally marked with largish brown cross-bars or 

 sjjots. The interior is white, variously stained with purplish or violet-brown. The 

 hinge is not very strong and narrow. The central tooth in the left valve and the two 

 posterior in the right are grooved or bifid at the top. The anterior scar is subovate, the 

 posterior broader, rounder. The pallial sinus is small, narrow, and sharply rounded at 

 the apex. The margin is very finely crenulated along the lower part, and most minutely 

 on the posterior and anterior slopes, remarkably so at the lunule. 



Length 21-^- mm., height 16^, diameter 10. 



Length 18 mm., height 15^, diameter 10. 



Habitat. — Station 212, south of the Philippine Islands, in 10 to 20 fathoms; sand. 



This species has a close resemblance to Venus maricu, Linn., and indeed was confused 

 with it by M. Deshayes when he named the Veneridfe in the National Collection. It is 

 distinguished from that species by its generally narrower posterior end, closer and 

 coarser beaded radiating costse and concentric ridges, the latter posteriorly forming 

 longer thin erect lamellae and not short scales as in Veims marica. In the latter the 

 dorsal area is sculptured with fine radiating granulose lirae which ai-e wanting in VeJius 

 recognita, in which species the denticulation of the margin is very much finer than in the 

 Linnean form. Venus costellifera, Adams and Reeve, is another closely allied species, 

 but has not the posterior lamellae of the present one, coarser crenulation on the margin, 

 particularly at the lunule, and is radiately ridged on the dorsal area. 



Venus (CJiione) lionotu, n. sp. (PI. III. figs. 7— 7b). 



Testa parva, inagquilateralis, alba, vel dilute rufescens, antice in medio aliquanto 

 acute rotundata, postice inferne subproducta, magis acute cui-vata, ad marginem 

 inferiorem late ■ arcuata, fortiter cancellata. Lunula magna, distincta, elongato-cordato, 

 liris tenuibus radiantibus circiter sex, incrementi lineis concentricis decussatis instructa. 

 Area insignis, subdiaphana, haud radiatim lirata, terminis obsolctis lirarum concentri- 



