some new and peculiar Mollusca. 497 



Nea'ra notahilia'^'j Jeffr. 



Shell oval, convex, tliin, opaque, somewhat glossy : sculp- 

 ture, none in the umbonal region (which is quite smooth), but 

 on the anterior side and in front are about 30 fine concentric 

 and equidistant lamellar ridges or striae ; the rostrum on the 

 posterior side is defined by two keels, the lower one slanting 

 and the upper fiexuous ; the posterior side is transversely 

 Avrinkled in a fibrous manner ; the whole surface appears, 

 under a microscope, to be covered with minute and close-set 

 stria, which run parallel to the ridges and obliquely on the 

 posterior side : colour white : vianjins rounded on the anterior 

 side and in front, indented under the rostrum, which is rather 

 short and gently curved at the point, straight behind : heaks 

 small, incui'vcd towards the anterior side; umbones prominent : 

 cartilage narrow ; pit or receptacle sunk under the beaks : 

 hinfje-line nearly straight, except where it is internipted by 

 the beaks : Innfje-plate narrow and slight, slightly folded back 

 on the upper part of the anterior side in the left valve : teeth, 

 a lateral one on each side in the right valve, both of which 

 laterals are triangular and erect near the beak, and thin off as 

 ridges towards either side : inside glossy, exhibiting the im- 

 pression of the rostral keels : scars indistinct. L. 0"2. B. 0*35. 

 Station 12, 1450 fms. ; two valves and fragments. Some 

 of the fragments show that this species attains a larger size 

 than that given in the description. 



Necera circinata'\, Jeffr. 



Shell roundish-oval, obliquely twisted towards the pos- 

 terior side, convex, rather solid, opaque, and of a dull hue : 

 sculpture, scarcely any in the umbonal region, about 25 fine 

 concentric and equidistant lamellar ridges or strias in the 

 middle of the shell, Avhich become confluent in front and dis- 

 appear at the sides ; the rostrum has two keels (as in the last 

 species), which radiate from tlie beak; the posterior side is 

 also wrinkled transversely ; between the ridges are minute 

 but not numerous concentric striae : margins rounded on the 

 anterior side, sloping with a gentle curve in front (the curve 

 being greatest towards the posterior side), indented at the 

 conmiencement of the rostrum, straight behind, and somewhat 

 upturned at the posterior end ; rostrum triangular, Avith a 

 curved slope downwards : beaks as in other sjiecies ; umbones 

 not so prominent as in the last : cartilage oval ; pit not much 

 sunk below the beaks : hinge-line nearly straight, but (viewed 



• Remarkable. t Rounded. 



