388 MR. E. A. SMITH ON THE [Apf- 18, 



teriorly, with the arcuate margin red, and reddish on the inner surface, 

 with two pale rays from the nucleus, one central and the other sub- 

 marginal, the extreme edge being blackish. In all these respects it 

 coincides with that of N. gaqates, Lamarck, from the Mauritius ; 

 and the terminal processes are similar in both forms. Von Martens's 

 conjecture that the species might belong to B. retifera, Benson 

 (Couch. Cab. p. 283), is not to be wondered at, considering the 

 briefness of Reeve's description, and the fact of only the back of the 

 shell being figured. 



B. CONCHIFERA. 



CORBICULA MADAGASCARIENSIS, Sp. nOV. (Plate XXII. figS. 



25-27.) 



Shell a little inequilateral, rounded and narrow in front, much 

 broader, squarish, and subtruncate posteriorly, arcuate along the 

 ventral margin, finely concentrically striated ; yellowish, greenish 

 down the posterior side. Umbones a little prominent, incurved, 

 situated a little anteriorly. Interior lilac, with two or three rather 

 distant concentric purple zones, stained with dark purple down the 

 posterior side, and with a smaller stain of the same colour at the an- 

 terior side. 



Length 11| millim., width 14, diameter 7. 



Hab. Twenty miles from Antananarivo {Johnson). 



The concentric strias are deep and regular upon the umljones ; but 

 towards the ventral margin they become less regular and finer, and 

 in front are rather more strongly developed than towards the pos- 

 terior side. This is the first record of the genus in Madagascar ; 

 and I have not been able to associate the species with any of the forms 

 described from the adjacent continent. 



Sph^rium madagascariense, Tristram. 



Sphcerium madagascariense, Tristram, Proc. Zool. See. 1863, p. 6 1 ; 

 Sowerby, Conch, Icon. pi. iii. f. 22, bad ! 



Hab. Two days west of Antananarivo {Tristram) ; about 20 miles 

 from the capital {Johnson) ; Betsileo {Cowan). 



This species is scarcely if at all different from S. capense of Krauss, 

 and is mainly distinguished by difference in locality. The slight 

 compression of the valves towards the circumference, remarked upon 

 by Tristram, is not constant in all specimens, some exhibiting it in a 

 comparatively decided manner, whilst others are rounded at that part 

 just hke the South-African form. 



LiMOSlNA FERRUGINEA, KraUSS. 



Cyclas ferruginea, Krauss, Sudafr. Moll. p. 7, pi. i. f. 7 ; Clessin 

 (as Limosina), Conch. Cab. p. 247, pi. 46. f. 1-4 ; Sowerby (as 

 Sphcerium), Conch . Icon. f. 4 7, not good ! 



Hah. The river Knysna, South Africa {Krauss). About 20 

 miles from Antananarivo (Johnson). Also Mauritius {Brit. Mus.). 



