252 MOLLUSCA FROM THE CRAG. 
large angular-formed or spoon-shaped depression for the ligament, before which, and 
immediately beneath the umbo, is a prominent A-formed tooth in the 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 the living animal is said to be in oozy sand, or muddy bottoms, 
varying in depth from six to twelve fathoms. 
Maca, Oken. 1815. 
Cuama (golar). Adanson. PsamMosia (sp.) Turt. 1822. 
Hypoema Hypocmoperma (sp.) Poli, 1791. SoLecurtus (sp.) Blainv. 1824. 
Srirquaria (part). Schum. 1817. Novacuttna?’ Benson, 1830. 
Apastus. Leach, MS. Fide Gray, CyrtosoLen. Herrm. 1847. 
PsaMMosoLENn. Bronn. 1831. MacnHa. 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 striz. 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 sinuated. 
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 So/ens, 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, Linneus. Tab. XXV, fig. 3, a, 6. 
SoLEN sTRIGILLATUS. Linn. Syst. Nat., ed. 12, p. 1115, No. 30, 1767. 
= = Chemn. Conch. Cab., vol. vi, t. 6, figs. 41, 42. 
= = ? Poli. Test. utriusq. Sic., vol. i, p. 21, t. 12, fig. 1. 
p— = Phil. Enum. Moll. Sic., vol. i, p. 5. 
— canpipus? Broce. Conch. Foss. Subap., p. 497. 
PsaMMOBIA stRiciLLaTa. Turt. Brit. Biv., p. 97, t. 6, fig. 13, 1822. 
SoLecurtTus stRigitLarus. Phil. Enum. Moll. Sic., vol. ii, p. 5, 1841. 
Macna striettuata. Gray. List Brit. Moll., p. 61, No. 1, 1851. 
Hypocma vartecaTa. Poli. Test. Sicil. utrius., vol. ii, p. 257. 
Spec. Char. Testa ovato-oblongd, subequilaterah, utrinque rotundatd, in media com- 
press, coarctatd ; dimidiam striatam, striis subobliquis insculptis. 
