18 TESTACEOUS MOLLUSCA. 
PANOPEA. 
Equivalve, transverse, gaping unequally at ihe sides; one conical 
primary tooth in each valve, and a compressed, not exserted, 
short, ascending callosity on one side ; ligament external, affixed 
on the elongated side of the shell, to the callosities. 
P. Auprovanpi.* Lam, 1.—Mya Giycimertis. Lin. Gimel. 
3222.— D.p. 41.—Ch. f. 25.— Don. t. 142.— Wood. G. C. t. 25. 
f. 1.—W. t.3. f. 41. Oblong subrhombie, very thick, pale fulvous, 
with strong concentric wrinkles, gaping and obliquely subtruncated 
at both extremities, ventrally ineurved. 43 ..835.— Mediterranean. 
P. Zevanica. Quoy. Ast. t. 83. f. 7, 8,9. Regularly oval- 
oblong, subequilateral, transversely and irregularly wrinkled, anterior 
end nearly closed, posterior with a very wide gape; umbones very 
small and but little prominent.—N. Zealand. In form and size 
it approaches the Lutrarie. 
P. Austranis. Sow. G. f. 2.—fReeve. t. 27. f. 2. Ovate-ob- 
long, transverse, roughly wrinkled concentrically, rather broad at 
the anterior end ; all but truncated obliquely at the shorter poste- 
rior extremity. 
P. Arctica. Gould Mas. p. 37. f. 27.—Giycimeris A. Lam. 
— Oblong, somewhat cylindrical, strong, anterior side twice as long 
as the rounded posterior and truncated; widely gaping at both ends, 
traversed by two radiating wavelike ridges which divide the surface 
into three portions. 12..24.—Nenjoundland. Not unlike Mya 
Truncata.4 
GLYCIMERIS. 
Transverse, gaping widely at each extremity ; hinge callous, 
destitute of teeth; ligament external. 

PHOLADOMYA. 
Thin, rather hyaline, transverse ventricose ; posteriorly short and 
rounded, anteriorly slightly elongated and gaping, the dorsal edge 
also gaping a little : hinge with a small rather elongated triangular 
pit, and a marginal lamina in each valve, to the outer part of which 
is attached the rather short external ligament ; muscular impres- 
sions two, which as well as the palleal scar are indistinct. 
P. Canpipa. Sow. G.—Reeve. t. 32. Oblong, white, the 
central portion covered with decussated divaricating striz, which 
proceed from the umbo downwards. 23..13. 
1 A most elegant species with radiating ribs, which I have lately 
seen, has, I believe, been described by Eichwold (as a Glycimeris), 
in his account of the shells of the Caspian Sea. I have not suc- 
ceeded in procuring the work, and consequently cannot give a name 
to the species. 
