ccxliv 
APPENDIX^ 
Species. — C. Radiatum. 
Cardium edentulum. Mont. Supple., 29. 
Mactra radiata. Don., t. 161. 
Family. — AncADiE. 
Genus. — Arca. Lam. 
Species. — A. glacialis 
Testa, ovali-elliptica, tenui, villosa, alba, concentrice et transversim 
striata ; postice rotundata ; umbonibus approximate ; dentibus sub-obsoletis ; 
margine integerrimo. 
Arca glacialis. Gra^, ut supra. 
Shell, thin, oval, elliptical, rounded before and behind, regularly, finely 
concentrically, and transversely striated; epidermis, silky; umbones, to- 
wards the joint, incurved, nearly close ; intermediate space, lanceolate, 
ventricose ; margin, even, thin ; hinge-teeth very small, indistinct in the 
middle, rather larger at each end ; length 3-4ths of an inch, depth 3-8ths, 
breadth 4-5ths. 
Animal, mantle lobes separate ; foot flat, compressed, subquadrate, front 
two cut, with one or two fibres from the lower edge ; trachea none. 
Family. — MYTiLioiE. 
Genus. — Modiola. Lamarck. 
Shell longitudinally obliquely striated. 
(Modiola Arctica, of Dr. Leach, in Ross’s Voyage, is 
Mytilus Fabr., O. Fab., Fauna Grcenlandica, 419. 
— Chemnitz, viij., 184. t. 85. f. 761.) 
Shell, middle smooth, simated, before and behind, generally striated. 
Species I. — Modiola nigra. 
Modiola discrepans. Leach. Ross’s Voyage, not of Lamarck, 
Mytilus discrepaiis. Mont. Ri it. Shells, t. 26. f. 4, 
Species 2. — Modiola Icevigata. 
