MACTRA.— Plate XX. 



compresse attenuato ; lunula subcordatd ; umbonibiis 

 parvis, appj'esds. 



The Thracia-like Mactea. Shell ovate, gibbous aa- 

 teriorly, gaping at both ends, inequilateral, thin, 

 opake-white, concentrically densely fibrous-striated, 

 obliquely undulately wrinkle-plaited, anterior side 

 rounded, posterior compressly attenuated ; lunule 

 subcordate ; umboes small, appressed. 



Adams and Eeeve, Zool. Voy. Samarang, MoU. p. 81. 

 pi. 33. f. 8. 



Hab. Eastern Seas ; Belcher. 



The chief peculiarity of this species consists in the 

 waved rib-like plaits undulating upwards on the posterior 

 side, contrary to the curious fibrous-like strise of growth. 



Species 117. (Mus. Cuming.) 



Mactea capillacea. Mad. testa transverse oblongd, 

 valde incequilate/'ali, tttrinqice hiante, temd, Candida, 

 epidermide stramined indutd, concentrice rude striata, 

 radiatim subtiliter imdtdato-corrugaUm striatd, latere 

 antico brevissimo, rotmidato, postieo compresso-pro- 

 ducto, subrostrato ; umbonibus parvis. 



The steingy Mactea. Shell transversely oblong, very 

 inequilateral, gaping at both ends, thin, white, co- 

 vered with a light straw-coloured epidermis, concen- 

 trically rudely striated, radiately finely wave-wrinkle 

 striated, anterior side very short, rounded, posterior 

 compressly produced, somewhat beaked ; umboes 

 small. 



Deshayes, Pro. Zool. Soc. 1854. 



Hab. Philippines and mouth of the Indus. 



A delicate posteriorly produced species, distinguished 

 by a striking peculiarity of sculpture, the surface being 

 rayed with fine close-set cross-waved wrinkled striae. It 

 has been found of a very much larger size than that of the 

 shell here figured. 



Species 118. (Mus. Cuming.) 



Mactea pellucida. Macf. testa transversim oblongd, 

 cowpressd, utrinque Jtiante, iiUBquilaterali, alba, sub 

 lente minutissime decussatim striata, versus margines 

 epidermide tenui Jlavicante indutd, latere antico ro- 

 tundato, postieo subproducto ; umbonibus parvis, ap- 

 proximatis. 



The pellucid Mactea. Shell transversely oblong, 

 compressed, gaping at both ends, inequilateral, white, 

 beneath the lens very minutely finely decussately 

 striated, covered towards the margins with a thin 

 yellowish epidermis, anterior side rounded, posterior 

 rather produced ; umboes small, close. 



Chemnitz, Conch. Cab. vol. vi. p. 335. pi. 34. f. 334. 

 Mactra depressa, Lamarck. 



Hab. Bay of Manila. 



A smooth, rather compressed species, of which the sur- 

 face has a somewhat silky appearance, occasioned by ex- 

 tremely minute crossed striae. 



