IIEFORT ON THE LAMELLIBRANCHIATA. 231 



Habitat. — Simon's Bay, Cape of Good Hope, in 15 to 20 fathoms. 



The above description is based upon the specimens obtained by the Challenger. 



This is the first record, I believe, of the existence in a living state of this most interest- 

 ing species. The genus is already known as recent, one species from the Catalina Islands 

 having been described by Carpenter as NucuUna munita, and another from the Korean 

 Straits by A. Adams under the name of Huxleyia sulcata. 



Only three left valves of this species were obtained. They differ from Crag 

 specimens in being larger, and consequently appear rather higher, as, with the growth of 

 the shell, the height increases more than the length. The hinge-teeth are precisely the 

 same in some of the fossil specimens, but usually appear to be somewhat fewer. 



I am not quite convinced that the Nucula miUaris of Deshayes, from the Paris Basin, 

 is the same species as the Crag shell. There appear to be certain differences in form, in 

 the somewhat pearly interior and position of the ligament w^hich distinguish the former. 



Mr Searles Wood ^ does not assign any reason for abolishing his name Pleurodon and 

 substituting for it that of Nucinella. It may have been that he found that the appella- 

 tion Pleurodonta- had previously been employed in the Mollusca, and in his judgment 

 that it too closely resembled the genus created by himself. Be that as it may, I do not 

 think he was justified in assigning a new name to this genus, seeing that d'Orbigny in 

 the meantime had suggested that of Nuculina.^ 



Leda, Schumacher. 



Leda semen, n. s}). (PL XIX. figs. 2-2a). 



Testa minuta, couvexa, inajquilatcralis, oljlouga, antice acute rotundata, postice 

 breviter rostrata, extremitatem versus radiatim impressa, incrementi lineis tenuiter 

 striata, sordide albida. Margo dorsi anticus elougatus, leviter convexus et declivis, 

 posticus brevior, primo rectiusculus, dein ad extremitatem curvatus. Margo inferior late 

 arcuatus, postice leviter sinuatus. Umbones aliquanto prominentes, involuti, postice 

 inelinati, postmediani. Linea cardinis mediocriter valida, deutibus novenis posterioribus. 

 duodcnisque anterioribus instructa. Fossa ligamenti triangularis, profunda. 



This very small species is fairly solid, very inequilateral, elongate, sharply rounded at 

 the anterior end and shortly beaked behind, the point, however, not being very acute. 

 The valves exhibit a broad shallow depression down the posterior side, which causes, at 

 that part, a faint sinuation in the otherwise regularly and broadly curved lower outline. 

 The dorsal margin is oblique on both sides, slightly excurved in front, straightish at first 

 behind, and then curving downwards to the extremity. The sculpture consists of very 

 iine lines of growth only. The beaks are a little prominent, curve inwards towards one 



' Monog. Craj; Moll., vol. ii. p. 72 (1852-55). - Fischer de Waldlicim Mus. Doiuidof., iii. (1807). 



3 Paliont. Frang. Terr. Cret., t. iii. p. 161 (1843). 



