M A C T R A . 



Plate IX. 



Species 33. (Mus. Cuming.) 



Mactea Sayi. Mad. testa, transversim ovatd, late sub- 

 trujond, compressimculd, snhaqidlaterali, solid'mscnld, 

 utroque. latere aqualiter dfcUvi et obtuso, inferni re- 

 gulariter arcuato, sub epidermide Jlavescente cretaceo- 

 albd, IcBvigatd, substriatd ; umbonibm minimis, acutis, 

 subobliqnls ; area lumddque indistinct^. 



Say's Mactra. Shell transversely ovate, broadly sub- 

 triangular, rather compressed, nearly equilateral, 

 rather solid, both sides equally slanting and obtuse, 

 regularly arched at the lower part, chalk-white be- 

 neath a yeDowish epidermis, smooth, finely substri- 

 ated ; umboes vei-y small, acute, a little oblique ; area 

 and lunule indistinct. 



Spisula Sayi, Gray, Ann. and Mag. Nat. Hist. 1837, p. 

 373. 



Hah. Florida. 



A stone-wbite compressed shell, covered with a strong 

 yellowish-olive epidermis. 



Species 34. (Mus. Cuming.) 



Mactra angulata. Mact. testa trarisvershii ovatd, tur- 

 gidd, Irigond, acute angulata, incequilateraU, ten.tii- 

 striatd, calcareo-albd, nitente, epidermide tenui sira- 

 mined indiitd, latere antico rotundato, postico anr/ii- 

 lato-rostrato ; Immld indistinctd, area perampld, medio 

 elevatd ; umbonibus tumid is, acute angulatis. 



The angled Mactra. Shell transversely ovate, turgid, 

 triangular, sharply angled, inequilateral, finely stria- 

 ted, chalk-white, shining, covered with a thin straw- 

 coloured epidermis, anterior side rounded, posterior 

 angularly beaked ; lunule indistinct, area very large, 

 raised in the middle; umboes swollen, sharply an- 

 gled. 



Gray, MS. in Brit. Mus. 



Hab. Gulf of California. 



Allied to M. Bonaciformis, though uniformly of larger 

 size. It is chiefly characterized by the large broad con- 

 cavely angled growth of the posterior area. 



Species 35. (Mus. Cuming.) 



Mactra olorina. Mact. testa transversim ovatd, trigond, 

 tumidlusculd, iiKsquilaterali, lavigaid, nitente, antice 

 dense transversim striata, incarnato-albd, ejndermide 

 stramined prope viarginem indutd, latere antico ro- 

 tundato, postico rostrato ; wmbonibus subcompressis ; 

 hinuld obloiigo-ovatd, striata, area elongald. 



The swan-like Mactra. Shell transversely ovate, tri- 

 angular, rather swollen, inequilateral, smooth, shin- 

 ing, anteriorly closely transversely ridged, flesh-white, 

 covered near the margin with a straw-coloured epi- 

 dermis, anterior side rounded, posterior beaked ; um- 

 boes subcompressed ; lunule oblong-ovate, striated, 

 area elongated. 



Philippi, Abbild. und Besch. Conch, vol. ii. p. 72. pi. 3. 

 f. 3. 



Hab. Red Sea. 



A delicate flesh-white polished shell, densely ridged on 

 the anterior side only, and peculiarly beaked at the pos- 

 terior extremity. 



Species 36. (Mus. Cuming.) 



Mactra ovalis. Mact. testa transversim ovatd, com- 

 pressiusculd, subaquilaterali, transversim rude striata, 

 sordide alba, epideruiide /iilvo-oli.vaced crassinsculd 

 indutd; wmbonibus compressis, approximatis ; lunula 

 aredque indistinctis ; sinu pallii prof undo. 



The oval Mactra. Shell transversely ovate, rather 

 compressed, nearly equilateral, transversely rudely 

 striated, dirty-white, covered with a rather thick ful- 

 vous-olive epidermis ; umboes compressed, approxi- 

 mated ; lunule and area indistinct ; sinus of the man- 

 tle deep. 



Say, Journ. Acad. Nat. Sci. Philadelphia, vol. ii. p. 309. 

 Spisula similis. Gray. 

 Mactra ponderosa, Philippi. 



Hab. Massachusetts, United States. 



More truly ovate than M. Sayi, and of rougher growth, 

 with the lunule and area much less distinct. It attains a 

 much larger size than is represented in the accompanying 

 Plate. 



April, 1854. 



