252 MOLLUSCA FROM THE CRAG. 



large angular-formed or spoon-shaped depression for the ligament, before which, and 

 immediately beneath the snibo, is a prominent A-formed tooth in tlie right valve, 

 which fits into an angular depression in the left. The comparative dimensions are 

 somewhat variable, like what is observable in the living shell. 



The habitat of tlie living animal is said to be in oozy sand, or muddy bottoms, 

 varying in depth from six to twelve fathoms. 



Macha, Oken. 1815. 



CiiAMA (golar). Adanson. 

 IIypog.ea IIypogj::odeuma (sp.) Poll, 1791. 

 SiLiQUARiA (part). Schum. 1817. 

 .4dasil"s. Leach, MS. Fide Gray. 

 PSAMMOSOLEN. Bronii. 1831. 



PsAMMOBiA (sp.) Turt. 1822. 

 SoLECUiiTUS (sp.) Blainv. 1824. 

 NoVACULiNA? Benson, 1830. 

 Cyktosolen. Herrm. 1847. 

 Macua. Agass. 1839. Gray, 1851. 



Generic Character. Shell transverse, of a somewhat oblong form, compressed in 

 the middle, equivalved, equilateral ; rounded and gaping at both extremities ; surface 

 generally ornamented more or less with oblique grooves or striae. Hinge composed of 

 two diverging teeth in one valve, and one in the other, with a large fulcrum for an 

 external ligament. Impression of the mantle deeply sinuatcd. 



Animal oblong, large and thick, mantle widely open in front for the passage of a 

 large tongue-shaped foot. Siphons long, deeply separated, but united at their bases. 



This has been justly separated from the Salens, on account of the different position 

 of the hinge, though in its habits there is great similarity, and it is capable of burying 

 itself rapidly in the sand. 



Fossils, probably belonging to this genus, have been obtained from the middle 

 Secondary Period. 



Macha strigillata, Linnam. Tab. XXV, fig. 3, a, b. 



SoLEN STKIGILLATUS. Linn. Syst. Nat., ed. 12, p. 1115, No. 30, 1767. 



— — Chemn. Conch. Cab,, vol. yi, t. 6, figs. 41, 42. 



— — ? Poll. Test, utriusq. Sic., vol. i, p. 21, t. 12, fig. 1. 



— — Phil. Enum. JIoll. Sic, vol. i, p. 5. 



— CANDIDUS? Broc. Coiicli. Fosa. Subap., p. 497. 

 Psammobia STKIGILLATA. Tvrt. Brit. Biv., p. 97, t. 6, fig. 13, 1822. 

 SoLECURTUS STRIGILLATU8. Phil. Enum. Moll. Sic, vol. ii, p. 5, 1841. 

 Macha stbigillata. Gray. List Brit. .Moll., p. 01, No. 1, 1851. 

 llYPor..T:A vauiegata. Poll. Test. Sicil. utrius., vol. ii, p. 257. 



Spec. Char. Testa ovato-ohlongd, siibaqiiilaterali, utrinque rotundatd, in media com- 

 pressd, coarctatd ; dimidiam striatam, striis subobliquis insculptis. 



