EEPORT ON THE LAMELLIBRANCHIATA. 241 



from the anterior end. The hinge-teeth are al)out thirty in number and remarkabl}' 

 excavated on the outside, those on the longer side being rather more numerous than 

 those on the anterior margin, only extending along a trifle more than half its lengtli. 

 The interior of the valves is glossy, and along the middle of the rostrum exhibits a. 

 slight curved ridge. 



Length 5j mm., height 2|, diameter 1-|. 



Habitat. — Station 185, east of Cape York, North Australia, in 135 fathoms; coral 

 sand. 



Externally this curious little shell recalls to mind certain little rostrate forms of tlio 

 genus Necera. 



Leda ramsayi, n. sp. (PI. XX. figs. 3— 3a). 



Testa elongata, antice acute rotundata, postice producta, anguste rostrata, compressa, 

 valde insequilateralis, bicarinata, carinis ab umbonibus ad extremitatem posticam decur- 

 rentibus, concentrice suljfortiter lirata, liris supra carinam inferiorem subito angulatis. 

 Margo dorsi antieus leviter convexus, valde declivis, posticus fere duplo longior, incur- 

 vatus, minus oblicpius. Ventris margo late arcuatus, postice hand profuude sinuatus. 

 Area postica dorsalis lanceolata, concava, incrementi lineis tenuissimis striata, carina 

 superiori filiformi marginata. Umbones Iseves, nitidi, longe ante medium collocati. 

 Dentes numerosi, conferti, angulares. Pagina interna nitida, ad extremitatem rostri 

 porca mediani brevi instructa. 



This species is rather longly rostrate behind and sharply rounded in front. It is 

 very inequilateral, the acute smooth umbones being situated at about one-third of the 

 entii-e length of the shell from the anterior end. The front dorsal slope is short, veiy 

 oblique, and somewhat excurved, the posterior, on the contrary, being very long, less 

 sloping, and gently concave. The lower outline forms a broad curve with a very faint 

 sinuatiou near the hinder shortly truncate end. The valves have two radiating ridges, 

 whereof the upper is slender, keel-like, and extends from the apex to the uj)per corner 

 of the rostrate extremity, the lower being rounded, broader, and descending to the 

 inferior angle. The sculpture consists of rather strong concentric lirse, which are 

 suddenly turned at right angles upon the slightly concave space between the radiating 

 keels, and, owing to the produced character of that side of the valves, are further apart 

 than on the other portion of the surface. The hinder dorsal area is concave, almost 

 smooth, and sharply defined by the uppermost carina. The teeth are numerous, close- 

 set, and angular, those on the posterior side extending along two-thirds of its length. 

 Along the middle of the rostrate end internally is a short curved ridge. 



Length 7 mm., height 4, diameter 2 . 



Habitat. — Station 164, off Sydney, New South Wales, in 950 fathoms; greerf mud. 



(ZOOL. CHALL. EXP. PART XXXV. — 1885.) Jim 31 



