APPENDIX. oa 
jf. 5. Cordate-subtrapeziform, very obliquely transverse, moderately 
strong, tumid, glossy, yellowish white, stained and spotted with 
ruddy flesh-colour in front, ridged throughout, except on the concave 
anterior slope, with numerous rounded lyre; ventral edge sub- 
arcuated, retuse in front; anterior side much produced, its extremity 
obliquely biangulated, the edge rectilinear; umbonal ridge pro- 
jecting, carinated. 1...14. China. The ridyes are not so close or 
numerous as in I. Vulgaris. 
On Arca (p. 151). The description of A. imbricata (p. 152) is 
from Bruguiéere, but unless both Reeve and myself should be mis- 
taken, the expression “rhomboidal oblong” would be more appro- 
priate than “ovate.” The copied synonymy is not to be trusted to. 
A. cardissa (p. 153) is only a distorted tetragona (p. 152); A. Gai- 
mardi (p. 155) a form of A. lactea (p. 154). Wood's figure of 
A. Brasiliana (p. 158) does not exhibit the features of that shell. 
For additional species consult the monograph by Reeve (Conch. Ic.); 
see, likewise, Ann. Nat. 1842, Lesson in the ‘ Coquille,’ J. Philad. 2, 
Zeit. Mal. 1845, 1847, 1848, 1851, D’Orb. 8S. Am. and Cuba Shells, 
Pr. Bost. 2, 3, J. Conch. 2, and Dunker’s Guinea Shells. 
Arca tetragona, p. 152, t. 19, f. 18 ... A. imbricata, p. 152, t. 18, 
f. 35 ... A. trapezina, p. 1538, t. 18, f. 56 ... A. gradata, p. 155, 
t. 18; £39 ..2 A. Pacifica, p. 155, t. 18,. £59 ..> A.edwanieaia, 
p-. 155, t. 18, f. 58 ... A. solida, p. 155, t. 18, f. 54 ... A. truncata, 
p- 156, t. 19, f. 14 ... A. alternata, p. 156, t..19, f. 1... A. velata, 
p- 156, t. 19, f. 17 ... A. mutabilis, p. 156, t. 18, f. 52 ... A. litho- 
domus, p. 156, t.19, f 2... A. glacialis, p. 156, t.19, f.8 ... A. anti- 
quata, p. 157, t. 18, f. 50... A. Deshayesti, p. 157, t. 18, f. 42... 
A. incongrua, p. 159, t. 18, f. 44 ... A. labiosa, p. 159, t. 19, £3... 
A. pexata, p. 159, t. 18, f. 43 ... A. concinna, p. 160, t. 19, f. 4... 
A. obesa, p. 160, t.19, f.5 ... A. labiata, p. 160, t.19, f.7 ... A. nue, 
p: 160, t.119, £ 6... A. formosa, p..160, t. 19, £.9 ....A: grandis, 
p- 160, t. 19, f.10 ... A. emarginata, p. 161, t. 18, f. 60 ... A. tuber- 
culosa, p. 161, t. 18, f. 53 ... A. Cardiiformis, p. 161, t. 19, f. 11... 
A. multicostata, p. 161, t. 19, f. 12... A. transversa, p. 161, t. 18, 
f. 57 ... A. auriculata, list of plates, p. 17, t. 14, f. 55. 
* (Byssoarce). Ventral edge hiant, not regularly toothed or 
notched. 
Arca ImBRicaTa (t. 18, f. 36), Poli, t. 25, f. 10, 11, teste Phil. 1, 
p. 58.—A. PULCHELLA, Reeve, I. Arc. f. 122. Small, subrhombic, 
subventricose, very inequilateral, of an uniform dirty white, densely 
fimbriated by broad membranaceous lamelle, which are crimped 
throughout by shallow radiating sulci, that are divergent on the re- 
tuse umbonal slope: ventral edge incuryed in the middle, curving 
