REPORT ON THE LAMELLIBRANCHIATA. 207 



Area chalcanthum is certainly ;i slightl}- .shorter form of tlii.s species, with which it 

 exactly corresponds iu all other respects. Both are said to have been obtained at the 

 Pliilippine Islands. 



Area [Scapharcaf) incequisculpta, n. sp. (PI. XVII. figs. 8-8c). 



Testa parva, oblique truncato-ovata, ventricusa, ina^qiiilateralis, alba, epidei'midc tcnui, 

 aliquanto fibrata, iuduta, concentrice radiatimque tenuiter lirata, cancellata. Latu.s 

 anticum obliquissime late arcuatum, posticum subperpendiculariter c-ur\atuiu. Margo 

 ventris subsemicircularis, antice oblique ascendens. Umbones vix promiuuli, parvi, 

 paululum remoti, haud acuti. Area dorsalis angusta, paulo impressa, margiuibus carinatis 

 prnecipue posterioribus circumdata. Dentes haud uumerosi, utrinque a medio divergentes. 

 Pagina interna all^a, in valva sinistra prope margiuem sulco punctato-denticulato ornata. 



This species is about as high as long, obliquely ovate, truncate above, rather 

 veutricose, inequilateral, inequivalve, of a pure white colour, in fresh specimens more 

 or less covered with a thin and somewhat hairy epidermis. The valves are rather 

 glossy, thinnish, sculptured with fine concentric grooves and intervening raised lira;, 

 wliich are excessively fine at the sides and a little thicker at the middle. These are 

 crossed by other rather finer lirae which radiate from the umbones and produce a finely 

 cancellated surface. They are rather more elevated in the right valve than in the left. 

 The dorsal line occupies the whole length of the shell, the angles formed by its 

 conjunction with the sides being rather greater than right angles. The ventral outline is 

 very arcuate, ascending obliquely in front, and more suddenly behind, on which side the 

 margin is very slightly curved and almost perpendicular. The opposite is more arcuate, 

 and curves obliquely towards the base. The umbones are not large, only a trifle raised 

 above the hinge-line, not acute, a little remote from one another, and located at about 

 one-third of the entire length of the shell from the anterior end. The ligamental area is 

 narrow, somewhat broader in front of the beaks than behind them, a little sunken, and 

 bordered with carinnte margins, especially posteriorly. The hinge-teeth are not very 

 numerous, being about seventeen to twenty, divergent on each side of the centre. 

 The interior is white, in young specimens at times exhibiting more or less radiate 

 subpunctate grooving. In the left valve, just within the margin, there is a narrow 

 punctate and finely denticulated groove, which receives the margin of the op]iosite valve. 



Length 8^ mm., height 8, diameter 6^. 



Habitat. — Station 24, off Culebra Island, West Indies, in 390 fathoms ; Pteropod ooze. 



It is curious that in this species the radiating excessively fine lirse should be decidedly 

 more distinct and elevated in the right valve than in the left. It is closely related to 

 Area pectunculoides and Arcafrielei, but was pronounced distinct by the late Dr. Gwyn 



