358 MACTRIDiE. 



This very distinct species, which was long coufouuJed 

 with the Mactra solida, and was first distinguished 

 by the sagacity of Captain Brown, is by no means an 

 uncommon shell, occurring on all parts of our coast from 

 Jersey (S. H.) to Zetland (E. F.), usually in deeper 

 water than its congeners. It was first observed, how- 

 ever, at low water in the Frith of Forth. "We mention 

 a few localities to shew its range in depth : Penzance, 

 twenty fathoms (M'Andrew and E. F.); Fishguard in 

 eighteen fathoms (Jeffreys) ; Anglesey in nine to twelve 

 fathoms (M'Andrew); Isle of Man in fifteen to twenty- 

 five fathoms (E. F.); North Sea off Norfolk in twenty- 

 five fathoms (Stanley) ; Cape Wrath in fifty fathoms 

 gravel, and in the same depth on the Lingbanks off Zet- 

 land, forty miles from shore (M'Andrew). Its range on 

 the Irish coast is equally extensive. 



Loven enumerates it among Scandinavian shells, ranging 

 as far north as Fiumark. 



M. suBTRUNCATA, Da Costa. 



Decidedly inequilateral, triangular or trigonally ovate ; surface 

 partially covered with regular concentric grooves ; posterior end 

 more or less acutely anguluted below : umbones prominent : dor- 

 sal areas and lateral teeth sulcated. 



Plates XXI. fig. 8, XXII. f. 2, and (siphons) Plate L, fig. 3. 



Mactra subtrmicata. Da Costa, Brit. Conch, p. 198. — Mont. Test. Brit. p. .03, 

 and Suppl. p. 37, pi. 27, f. 1. — Linn. Trans, vol. viii. p. 71, 

 pi. ],f. 11, (badly).— Dorset Catal. p. 32, pi. 5, f. 10.— 

 TuRT. Conch. Diction, p. 82. — Turt. Dithyra Brit. p. 70. 

 — Flem. Brit. Anim. p. 427. — Macgil. Moll. Aberd. p. 

 289.— Brit. Marine Conch, p. 47.— Brown, 111. Conch. 

 G. B. p. 108, pi. 41, f. 7.— Index Testae, pi. 6, f. 23.— 

 Mawe, Conchol. pi. 8, f. 4. — Piiinpi'j, Neucr Conchyl. 

 Mactra, pi. 1,1'. 4. 



