MACTRA. 



Plate V. 



Species 17. (Mus. Cuming.) 



Mactra discoks. Macf. tedd rotmidato-ovatd, suhtri- 

 gond, crassi/isciiln, (pqwilaterali, reyulariter convexd, 

 ItBOUjatd, r/rkeo-all/d, ejiidermide nvjrlcante-fiiHcd ver- 

 sus maryinem indidd, latere postico subplamilato, an- 

 gulo ohtiiso siMiUter carinidato circmmcripto, umbo- 

 nibus parvis, coiiferlhii approximatis ; liinuld aredqne 

 pUcato-strixitis ; siiiit palUi hrevissimo. Into, semicir- 

 cularL 



The haksh Mactba. Shell rotundately ovate, some- 

 what triangular, ratlier thick, equilateral, regularly 

 convex, smooth, greyish-white, covered towards the 

 margin with a blackish-brown epidermis, posterior 

 side rather flattened, surrounded with a slightly 

 keeled obtuse angle, umboes small, closely approxi- 

 mated ; lunule and area plicately striated ; sinus of 

 the mantle very short, broad, semicircular. 



Gray, Faun, of New Zealand, p. 251. Mag. Nat. Hist. 

 1837, p. 371. 



Hub. New Zealand. 



Of ratlier solid rounded proportions, stone-white, here 

 and there faintly rust-tinged, covered near the margin with 

 a dirty black-brown epidermis. 



Species 18. (Mus. Cuming.) 



Mactra Meketriciformis. Mact. iestd ovato-trigond, 

 tenuiculd, veidricosis-n)iid,cord)formi, concetdrice tenui- 

 driatd, stricB in ared lunuldcpiie pUcato-elevcdis, sordid^ 

 albd, epidermide fiiscescente indutd, umbonibus atro- 

 violaceis, latere antico rotmidato, postko subelongato- 

 rostrato, intiis Ulacind; cardine angusto, in medio 

 promiiiente ; dentibus lateralibtcs lamellosis ; shiupaUii 

 bred, hdo, iiix iiijlexo. 



The Meretrix-shaped Mactra. Shell ovately trian- 

 gular, rather thin, very ventricose, heart-shaped, con- 

 centrically finely striated, striaj plicately raised in the 

 area and lunule, dirty-white, covered with a brown- 

 ish epidermis, umboes blackish-violet, anterior side 

 rounded, posterior somewhat elougately beaked, in- 

 terior Ulac ; binge narrow, prominent in the middle ; 

 lateral teeth lamellous ; sinus of the mantle short, 

 broad, scarcely inflected. 



Deshayes, Pro. Zool. Soc. 1834. 



Ilab. Port Essington ; Jukes. 



The name given to this species is intended to denote its 

 general external resemblance with the Cytherea mei'etrix. 



Species 19. (Mus. Cuming.) 



Mactra obesa. Mact. testd ovato-trigond, suJwordiformi, 

 crassiuscidd, veiitricosd, leevigatd, albd, epidermide fits- 

 cescente indutd, latere antico obtmo, subangidato-pro- 

 diictd ; ared luniddque pUcato-striatis, umionibus ap- 

 proximatis ; siini pallii brevi, lata, semielliptico ; den- 

 tibus lateralibus compressis. 



The stout Mactra. Shell ovately triangular, some- 

 what heart-shaped, rather thick, ventricose, smooth, 

 whitish, covered with a light brown epidermis, an- 

 terior side obtuse, posterior subangularly produced ; 

 area and lunule plicately striated, umboes approxi- 

 mated ; sinus of the mantle short, broad, semi-eUip- 

 tic; lateral teeth compressed. 



Deshayes, Pro. Zool. Soc. 1834. 



Ilab. Torres Straits, North Australia ; Jukes. 



Somewhat resembling the preceding species in fonu, 

 though perfectly distinct in detail, more soUd, ivory-white 

 about the umboes, and less beaked posteriorly. 



Species 20. (Mus. Cuming.) 



Mactra velata. Mact. testd ovato-oMongd, subtrigond, 

 crassiuscuJd, opaco-alhd, ferrugineo-tinctd, epidermide 

 airo-fiiscd indutd, inaqidlaterali, utrinque hiante, la- 

 tere postico subcarimdato ; ared luniddque snbangustis, 

 umbonibus confertim approximatis; dentibus laterali- 

 bus brevibus, fovea Ugamenti ampld. 



The clad Mactra. Shell ovately oblong, subtriangular, 

 rather thick, opake-white, rust-tinged, covered with a 

 black-brown epidermis, inec[uilateral, gaping at each 

 end, posterior side slightly keeled ; area and lunule 

 rather narrow, umboes closely approximated ; lateral 

 teeth short, ligamentary pit large. 



Philippi, Zeitschrift fiir Malac. 1848, p. 153. AbbOd. 

 vol. iii. pi. 3. f. 5. 



llah. Panama (on the reef) ; C. B. Adams. 



A rather solid rust-tinged opake-white shell, covered 

 with a rather thick dii-ty black-brown fibrous epidermis. 



March, 1854. 



