MACTRA.— Plate X. 



Species 41. (Mus. Cuming.) 



Mactra MiTis. Muct. testa, trigono-ovatii, tmnidd, tenui- 

 culd, suhcEqidlaterali, deiine teimistriatd, incarnato-spa- 

 diced, latei'ihus rotundads, postico superne declivi ; 

 Immld aredqne snbaugustis, eleganter striatis ; wn- 

 honibus parvu, approximatis. 



The ripe Mactra. Shell triangularly ovate, swollen, 

 rather thin, nearly equilateral, very closely finely 

 striated, flesh-tinged, fawn-colour, sides rounded, 

 posterior slanting at the upper part ; lunule and area 

 rather narrow, elegantly striated ; umboes small, ap- 

 proximated. 



Deshayes, Pro. Zool. Soc. 1854. 



Hab. Mouth of the Gambia, West Africa. 



A very simple character, and of a light flesh-tinged 

 fawn-colour. 



Species 42. (Mus. Cuming.) 



Mactra truncata. Mact. testd trigond, crassd, solidd, 

 (E(pdlaterali, sordide albd, zoim transverais fulvis sub- 

 distmdibm interdmn notatd, latere antico rotimdato, 

 postico subangulato et truncato ; mnbonibus minmis, 

 angulatis, approximatis ; lunuld indistinctd, ared suh- 

 ampld, ambabus medio subelevatis. 



The truncated Mactra. Shell triangular, thick, solid, 

 equilateral, dead-white, sometimes marked with trans- 

 verse distant fidvous zones, anterior side rounded, 

 posterior slightly angled and truncated ; umboes very 

 small, angled, approximated ; lunule indistinct, area 

 rather large, both slightly raised in the middle. 



Montagu, Test. Brit. sup. p. 34. 

 Pectunculus crassiusculus, Lister. 



Trigonella zonaria. Da Costa. 

 Venus rugosa, GmeUn. 

 Mactra subtruncuia, Donovan. 

 Mactra crassatella, Lamarck. 

 Spistda trtmcata, Gray. 

 Hah. Britain. 



A simple subtruncated triangularly ovate shell, of solid 

 gTowth, of a dead white cast, more or less covered with a 

 thin brownish epidermis. 



Species 43. (Mus. Brit.) 



Mactra elongata. Mact. testa transversim elongatd, 

 trigond, crassd, solidd, iruequilaterali, sordide albd, 

 epidermide fused indntd, transversim rtide striata, 

 striis ad extremitates plicato-ngosis, latere antico 

 brevi, truncato, postico duplo longiore, attenuato ; um- 

 bonibus compressis, confertis ; lumdd excavatd, subin- 

 distiiictd, ared longd, ongnstd. 



The elongated Mactra. Shell transversely elongated, 

 triangular, thick, solid, inequilateral, dead-white, co- 

 vered with a brown epidermis, transversely rudely 

 striated, strice pUcately rugose at the extremities, an- 

 terior side short and truncated, posterior twice as 

 long, attenuated ; umboes compressed, close-set ; 

 lunule excavated, rather indistinct, area long and 

 narrow. 



QuoY and Gaimard, Voy. de I'Astrolabe, pi. 111. f. 5-8. 

 Spisula elongata. Gray. 



Hab. New Zealand. 



A shell of solid growth, and of unusually oblong trans- 

 verse form. 



