162 MOLLUSCA FROM THE CRAG. 



Macbopiiylla. Chemn., 1784. 

 PsiLOi'us (sp.) Poll, 1791. 

 Gkypuus. Humph., 1797. 

 Lacinia. Id. 



Lazarus. Cuvier, 1800. 

 Arcinella. Srhum., 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 Foli, 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 arc some whose shells are elegantly orna- 

 mented with spines or foliations, while others arc 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 arc 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 

 Tcrtiarics. 



1. Chama gryphoides, LinncEus. Tab. XV, fig. 8 a — d. 



Concha rugata Rondelf.tii. Aldrov. De Test., lib. iii, p. 4.»8, 1623. 



Glouus undatus. Klein. Tent., p. 173, No. 3, t. xii, fig. 81. 



Concha kupium. Chemn. Conch. Cab., t. rii, p. 14."), t. li, figs. .ilO — 513. 



— GKYPiioiDES. Gault. Ind., part v, t. 101, lit. c — e. 



CiiAMA — Linn. Syst. Nat., ed. 12, No. IC"), p. 1139, 1767. 



_ _ Chemn. Conch. Cab., t. vii, t. li, figs. 510— .j 13, 1787. 



_ _ PoU. Test. Utr. Sic, vol. ii, p. 122, t. x.xiii, figs. 3, 4, and 20, 1795. 



— — Broc. Conch. Foss. Subap., p. 519, No. 2, 1814. 



— — ? Basterot. Bord. Foss., p. 8 1 . 



— — Bronn. Lethoea Geogn., vol. ii, p. 927, t. xx.vviii, fig. 11, 1838. 



— — Phil. En. Moll. Sic, vol. i, p. 68, vol ii, p. 49. 



— — Savigntj. Eg.vp'-' '• ■''■^"' P- -"• P'- -^'^> ^S*- ^' ' — •^• 



— — D'Orii^ny. Moll. de. Canar., p. KM, No. 178. 



