REPORT ON THE LAMELLIBRANCHIATA. 155 



Family I s o c A R d 1 1 d ^ (?). 



Callocardia, A. Adams. 



Callocardia (?) adamsii, n. sp. (PL VI. figs. 7-7h). 



Testa valde insequilateralis, cordata, ventricosa, alba, concentrice tenuiter lirata. 

 Umbones prominentes, magni, iucurvati, baud approximati, longe ante medium coUocati. 

 Margo dorsi posticus elongatus, declivis, leviter arcuatus, anticus brevior, paulo convexus. 

 Lunula magna, late cordata, infra umbones leviter depressa, in medio aliquanto prominens, 

 linea profunde incisa circumdata. Area postica lanceolata, incrementi lineis striata, sub- 

 concava, bene definita. Dentes cardinales valvse sinistra; duo irregulares, antico elongato 

 sinuoso, infra umliones sito, postico niiuore obliquo. Valva dextra dente unico elongato 

 irregulari munita. Ligamentum parvum profunde inter umbones supra marginem situm. 



This species is somewhat cordate, a little longer than high, very inequilateral, more 

 elongated and produced behind than in front. It is rather convex, moderately thick, 

 white, not glossy, and sculptured with close fine concentric thread-like lirse, which become 

 mere striae upon the lunule and the posterior dorsal area. The front dorsal margin is a 

 little excurved and rather abruptly descending, the posterior being longer, gently arcuate, 

 and obliquely inclined, forming together with the upcurved ventral outline a rather more 

 acute extremity than in front. The lunule is broadly cordate, a little concave imme- 

 diately beneath the beaks, a trifle elevated along the centre, and cu'cumscribed by a deeply 

 incised line. The posterior dorsal area is narrow, lanceolate, and defined by subcarinate 

 ridges extending from the beaks to the hinder extremity. The umbones are much 

 elevated above the hinge-line, and curve over considei-ably towards the front. They are 

 not quite adjacent, and terminate in minute smooth glossy apices which curve away some 

 distance from the centre of the lunule. The hinge-teeth are peculiarly irregular in form, 

 and not easily described. In the left valve there are two, of which the posterior one is 

 narrow, oblique, small, and located below the ligament. The anterior forms an inner 

 raised irregular sinuated and notched edge to the hinge-plate, being separated from the 

 upper hinge-margin by a deep irregular groove. The right valve has but a single elongate 

 tooth of a similar irregular conformation as the anterior in the opposing valve. The 

 ligament is yellowish-brown, rather small, short, and situated deeply between the 

 umbones. The interior of the valves is opaque white in parts, and bluish-white else- 

 where, and exhibits numerous largish shallow pits or punctures irregularly disposed. The 

 muscular scars and the pallial line are rather indistinct. 



Length 12f mm., height 11^, diameter 9. 



Habitat. — Station 348, south of Sierra Leone, at a depth of 2450 fathoms. 



It is doubtful whether this species really belongs to the genus Callocardia. It 

 agrees with it in its cordate form, the curved over beaks, and the impressed line 



