REPORT ON THE LAMELLIBRANCIIIATA. 247 



This species is sliaped nut uulike certain forms of Cytherea.- It is rather inequi- 

 lateral, ovate, somewhat convex, semitransparent white, and sculptured with regular fine 

 concentric lira? and intervening slender sulci. The front dorsal margin is almost 

 straight, and considerably oblicjue, the posterior being almost equally sloping, longer, 

 and a triHe more curved. The lower outline is gently arcuate and about equally 

 ascending at both ends, which are sharply rounded. The umbones are prominent, 

 incurved, smooth, glassy, and anteriorly inclined. The hinge-teeth, about thirty in 

 number, form one unbroken series from side to side, those in the centre under the 

 umbones being minute, whilst those at the sides are very long, erect, and acute. Owing 

 to the semitransparent texture of the shell, the pits for the reception of the correspond- 

 ing teeth in the two valves are distinctly seen on both the front and hinder dorsal 

 areas. The ligament is small, and placed in a narrow groove between the small teeth 

 just behind the' tip of the beaks and the dorsal edge, and is probably only very little, 

 if at all visible externally. The interior of the valves is smooth and highly glossy. 



Length 8 mm., height 6^, diameter 4. 



Habitat. — Station 33, off Bermuda, in 435 fathoms ; also Station 24, off Culebra 

 Island, West Indies, in 390 fathoms. 



On account of the glossy surface, the pallial line of this species is very indistinct. 

 It is very unlike the t5rpical forms of Malletia in texture, form, and sculpture, and it- 

 is questionable whether, in the living state (all the specimens under examination being 

 dead, separated valves), it is furnished with a similar kind of epidermis. As, however, 

 the hinge-characters are the same, it seems to me advisable at present to locate it in 

 this genus. 



Malletia cuneata, n. sp. (PI. XX. figs. 10— 10a). 



Testa parva, modice convexa, subovata, antice acute rotundata, postice angustata, 

 acuminata, alba, conceutrice teuuiter striata, striis latus posterius versus paulo evanidis. 

 Margo dorsi anticus brevis, arcuatim descendens, posticus longior, declivis, minime 

 excurvatus. Margo ventralis late rotundatus, postice perindistincte sinuatus. Umbones 

 prominentes, antemediani, involuti, hand acuti, antice inclinati. Linea cardinis medio- 

 criter valida, serie continua dentium ad triginta instructa, paucis prope umbones 

 minimis. 



This smaU species is considerably inequilateral, broader in front than behind, where 

 it is somewhat acuminately produced, rather convex, white, and sculptured with fine 

 concentric striae, which become less apparent towards the hinder extremity. The dorsal 

 margin is somewhat oblique on both sides, the anterior portion being gently arcuate, 

 the posterior almost twice as long and rather straighter. The ventral outline is widely 



