162 MOLLUSCA FROM THE CRAG. 
Macropuytia. Chemn., 1784. 
PsrtLopus (sp.) Poli, 1791. 
Gryeuus. Humph., 1797. 
LAcrInria. Td. 
Lazarus. Cuvier, 1800. 
ARCINELLA. Schum., 1817. 
Gen. Char. Shell thick, strong, and adherent, irregular, rugose or foliated 
externally, inequivalve, sub-equilateral, with a distant, unequal, somewhat involute 
umbo. Hinge with one thick, oblique, sub-crenulated, obtuse tooth in one valve, 
inserted into a corresponding depression in the other. Impressions of the adductor 
muscles elongato-oval, that by the mantle entire, or without an inflection. Ligament 
external. 
The figure of the animal of one species, as given by Po/i, has the mantle open in 
front, with the edges slightly fringed, long, sub-cylindrical, somewhat bent: foot with 
a projecting heel, and two short and ciliated siphonal tubes, not extending beyond the 
margin of the shell. 
Amongst the recent species of this genus are some whose shells are elegantly orna- 
mented with spines or foliations, while others are rough, and possessed of but little 
beauty, and the rugose exterior often forms a firm attachment for species of sponge, by 
which they are occasionally covered. 
The animal generally fixes itself by the left valve, though sometimes by the right, 
and specific distinctions have been formed in consequence, upon the belief that the 
same species always adheres by the same valve. Recent observations have proved 
the fallacy of this dependence. 
Animals belonging to this Genus are inhabitants of tropical or sub-tropical regions, 
and are not known in a living state further north than the Mediterranean. It is 
rather a modern genus, no true species being found in any formation older than the 
Tertiaries. 
1. CHAMA GRYPHOIDES, Linnaeus. Tab. XV, fig. 8 a—d. 
Concua ruGATA Ronpetetit. Aldrov. De Test., lib. ili, p. 458, 1623. 
GiLopus uNDATUs. Klein. Tent., p. 173, No. 3, t. xu, fig. 81. 
ConcHa RupIUM. Chemn. Conch. Cab., t. vii, p. 145, t. li, figs. 510—513. 
—  GrypHorpes. Gault. Ind., part v, t. 101, lit. c—z. 
CHAMA — Linn. Syst. Nat., ed. 12, No. 165, p. 1139, 1767. 
— — Chemn. Conch. Cab., t. vii, t. li, figs. 510—513, 1787. \ 
— —_ Poli. Test. Utr. Sic., vol. ii, p. 122, t. xxiii, figs. 3, 4, and 20, 1795. 
— — Broe. Conch. Foss. Subap., p. 519, No. 2, 1814. 
— — ? Basterot. Bord. Foss., p. 81. 
— — Bronn. Letheea Geogn., vol. ii, p. 927, t. xxviii, fig. 11, 1838. 
oo a Phil. En. Moll. Sic., vol. i, p. 68, vol ii, p. 49. 
— — Savigny. Egypt., t. xxii, p. 211, pl. xiv, figs. 8, 1—3. 
ae — D Orbigny. Moll. de. Canar., p. 104, No. 178. 
