224 



marked with very fine and light longitudinal striae. In the specimen 

 before me, both valves are alike gibbous : the shell is consequently equi- 

 valved, 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. 



CXLVI. 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, 

 as L. squamosa. Hither he also refers Ostrea bullata, and five other sup- 

 posed Ostrex, figured by Chemnitz, Tom. vu. Fig. 649, 650, 652, 653, 

 654. He also describes five fossil species found in the neighbourhood of 

 Paris: L, spathulata, L. bulloides, 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 for which 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 Bosc. P. x. Fig. 3 and 4, but little 

 is known. This shell has not, I believe, been found fossil. 



CXLVIIJ; Pandora. A regular, inequivalved, and inequilateral bi- 



