REPORT ON 'IHE LAMELLIBRANCHIATA. 263 



little raised abuve the duisal margiu, rather ai-ute, and about a millimetre apart. The 

 ligamental area is elougate diamond-shaped, much narrowed and produced posteriorly, 

 and exhibits traces of a black ligament in the form of two slender lines, converging to a 

 point from the umboues towards the hinder extremity. The hinge-plate is very slender, 

 and armed with about eighteen teeth, whereof eight are in front of the apices, the 

 remainder behind them being ol)lique, and separated from the others by a short non- 

 dentate portion of the hinge-margin. The interior of the valves is white and only the 

 least glossy. 



Length 11 mm., height 6|, diameter 4. 



Habitat. — Station 246, Mid North Pacific Ocean, at a depth of 2050 fathoms ; 

 bottom, grey ooze. Also Stations 71 and 73, west of the Azores, in 1675 and 1000 

 fathoms respectively ; and finally, Station 24, off Cnlebra Island, West Indies, in 390 

 fathoms. 



I have already recorded an instance of a species from very deep water in the 

 Atlantic, w^hich is all Init identical with another from a still greater depth in the Pacific 

 {vide Ccdlocardia atlantica and Callocardia 'pacifica), but here in this instance I am 

 unable to distinguish the examples from these two oceans. Such a distribution is an 

 eminently perplexing fact, a problem difficult of true explanation. 



Area (Barbatia) corpule7ita, n. sp. (PI. XVII. figs. 5—56). 



Testa tenuis, globosa, iuiuquilateralis, obliqua, altior (|uam longa, all)ida, epidermide 

 tenui olivaceo-fuscescenti, subfibrata iuduta, lineis, elevatis radiantibus filiformibus 

 aliisque concentricis minute cancellata. Umbones magni, iuflati, involuti, baud 

 approximati, latus anticum versus inclinati. Ai'ea dorsalis angusta, longitudinem testae 

 fere sequans. Ligamentum lineare, nigrum, post umboues positum. Latus anticum 

 late, aliquantoque irregulariter arcuatum, posticum subrectum. Margo ventris 

 semicircularis, antice oblique aclscendens. Pagina interna alba, confertim et radiatim 

 subpunctata. Linea cardinis angusta, dentibus irregularibus (in medio subobsoletis) 

 utrinque armata. 



This remarkable species is very thin, much inHated, oldique, truncate-ovate,, 

 inequilateral, white, and covered with a thin olive-brownish more or less hairy 

 epidermis. The sculpture consists of very numerous, excessively fine concentric hair- 

 like lirce which are crossed by others as close and fine or even more slender which 

 radiate from the umbones, together forming a minute cancellation, the points of contact 

 being raised into minute tubercles from which arise the ejaidernial haii's. One of these 

 radiating lines, on the right valve only (the corresponding place in the left being 

 marked by a faint depression), is twice as thick as the others and located on the 



