224 
marked with very fine and light longitudinal stria. In the specimen 
before me, both valves are alike gibbous : the shell is consequently 
equivalved, and therefore seems to point out the necessity either of 
altering the terms in the definition of this genus, or of forming another 
genus, to comprize those shells which, possessing the other characters 
of Pectens, are not formed of unequal valves. There is no separation 
at the hinge, nor at the sides of this shell, and consequently it cannot 
be referred to the following genus. 
CXLYI. Lima. A longitudinal, nearly equivalved, eared bivalve, 
with the beaks separated by a cavity. The hinge toothless. The hinge- 
pit, which receives the ligament, partly internal and partly external. 
These shells are removed from the preceding genus, or rather from 
that of Ostrea, by Lamarck, who considers their separation authorized 
by the similarity between each valve, and by the ligament being in a 
great part external. Ostrea lima, Linn, is referred by him to this genus, 
asZ/. squamosa. Hither he also refers Ostrea bullata, and five other sup- 
posed Ostrece, figured by Chemnitz, Tom. vn. Fig. 649, 650, 652, 653, 
654. He also describes five fossil species found in the neighbourhood 
of Paris : L. spathulata, L. hulloides, L. obliqua, L. dilatata, L.fragilis. 
I find, among my fossils, none which I can positively assign to this 
genus. Those which, I think, may be referred hither, are silicious spe- 
cimens from Wiltshire, in the neighbourhood of Tilsbury, which are 
injured in their lower side, and consequently do not show the hinge. 
CXLVII. Pedum. An eared, inequivalved bivalve, gaping at the 
lower valve, and having its beaks separated ; the hinge toothless, the 
ligament exterior, and fixed in a long and narrow groove ; the inferior 
valve notched. 
Of the shell forwhich this genus was formed by Bruguiere, and which 
has been figured by Favanne, Tab. 80, Fig. k. ; by Chemnitz, T. 8, 
Tab. 72, Fig. 669 and 670, and by Bose. P. x. Fig. 3 and 4, but little 
is known. This shell has not, I believe, been found fossil. 
CXLVIII. Pandora. A regular, inequivalved, and inequilateral 
