some new and peculiar Mollusca. 427 



ribs cover the whole surface. Some allowance may also be 

 made for " descent with modification " during the enormous 

 lapse of time which has taken place since the Tertiary epoch, 

 as well as for altered conditions of temperature. The same 

 remark is applicable to Discina fallens and D. Atlantica. 



In shape this species is allied to L. 8arsn (or L. crassaT) : 

 but the sculpture is very different ; it is not, like that species, 

 solid ; and the hinge-plate is not crenellated or notched. 



As to the specific name, I admit that there may be some 

 doubt whether this is the Ostrea nivea of Brocchi, to which I 

 once referred it ; and I have therefore adopted Mr. Wood's 

 name ovata. Brocchi, indeed, did not notice the furrow, 

 which is characteristic of Lima suhauriculata and L. elliptica ; 

 and his description and figure are not inappropriate to the 

 present species. Renier never described his Ostrea nivea^ and 

 merely published the name, with a remark that it came nearest 

 to 0. [Lima) inflata. Lima nivea of Risso and Philippi is 

 apparently L. suhauriculata^ with which Philippi himself sub- 

 sequently identified it. 



Lima suhovata *, JefFr. 



Shell somewhat oval, convex in the middle and compressed 

 towards the sides, thin, semitransparent, and glossy: sculpture^ 

 about 50 very fine and thread-like longitudinal ribs, which 

 radiate from the beaks and extend to the sides ; two of the 

 ribs in the middle are larger than the rest and are divided by 

 a straight furrow ; the ribs are crossed by numerous concentric 

 lines of growth : colour white : margins sharply curved in 

 front, and sloping on each side towards the middle, so as to 

 give the shell the shape of a hen's ^gg : beaks proportionally 

 large and prominent : ears triangular, well defined, and nearly 

 straight, with rectangular corners : cartilage small : ligament 

 narrow : hinge-line straight : hinge-'plate narrow, plain-edged : 

 cartilage-pit triangular, with a shelf or ledge on each side to 

 separate the ears : inside glossy, exhibiting the reverse or 

 underside of the ribs and central furrow. L. 0*25. B. 0T4. 



Single valves from Station 12, 1450 fras. '■ Porcupine ' 

 Exp., 1869, off the north-western coast of Ireland, 664-1443 

 fms. ; between the Hebrides and Faroe Isles in 542 fms., 

 and between the Faroes and Shetland in 125 fms. ^ Chal- 

 lenger ' Exp., off the Azores, 1000 fms. Palermo (Monte- 

 rosato) ! 



This species has a more oval shape find is shorter tliau 

 L. suhauriculata ; it is bluntly pointed in front and expanding 



* Somewhat oval. 



29* 



