MACTRA. 145 



Mactra, No. 12. Schroeter Einl. iii. p. 85. 



Inhabits the coasts of the Nicobar Islands. Chemnitz. Coast 

 of Dorsetshire, very rare. Pulteney. 



This Shell, in size, whiteness, and tenuity, much resembles 

 M. pel/ucida, but the anterior side is more angulated, and 

 the slope better defined. We have the authority of Mr. 

 Racket, who is acquainted with our English M . dealbata, for 

 considering it to be the M.J'ragilis, and not the M. pellu- 

 cida of Gmelin. Chemnitz says it has the habit of a Tellen, 

 but the hinge of a Mactra. 



rugosa. 34. Shell ovate-oblong, marked with strong 

 longitudinal and obsolete transverse striae; 

 margin crenuiated. 



Mactra rugosa. Chemnitz, vi. p. 236. t. 24. f. 236. Gme- 

 lin, p. 3261. 

 Mactra, No. 13. Schroeter Einl. iii. p. 85. 

 Enc. Meth. t. 254. f. 2. 



Variety. Sh< II smallt r and thinner. 

 Mactra rugosa Indiaa Orientalis. Chemnitz, vi. p. 238. 



t 24. f. 237. 

 Mactra Nicobarica. Gmelin, p. 3261. 

 Mactra, No. 14. Schroeter Einl. iii. p. 86. 



Inhabits the Mediterranean, and the variety the coasts of the 

 Nicobar Islands. Chemnitz. 



Shell about one inch and seven lines long, and two inches and a 

 half broad ; of a yellowish white colour, and marked with 

 crowded thick longitudinal stria?, which are crossed trans- 

 versely by other obsolete ones ; the two ends are somewhat 

 glabrous and smooth, the whole margin crenuiated, and the 

 inside chalky white ; Gmelin's M. JSIicobarica appears to be 

 only a variety, or probably a young shell, of this species. 



jEGYptiaca. 35. Shell oblong-oval, coated with a yel- 

 lowish epidermis, and longitudinally striated. 



Mactra JEgyptiaca. Chemnitz, xi. p. 218. t. 200. f. 1955 

 and 1956. 



Inhabits the Red Sea. Chemnitz. 



Shell about one inch long, and two inches broad, and may be 

 distinguished from the variety of M. rugosa, which it much 

 resembles, by being broader in proportion to its length. 



planata. 36. Shell oblong-oval, gaping, compres- 

 sed, thick, finely striated and ridged trans- 

 versely ; hinge without lateral teeth. 



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