18 TESTACEOUS MOLLUSCA. 



PANOPEA. 



Equivalve^ tt^ansverse, ffapintj imequally at the 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. Aldrovandi.* Lam. 1. — Mya Glycimeris. Lin. Gmel. 



3222.— -D. p. A\.— Ch.f. 25.— Bon. t. \i2.—Wood. G. C. t.2o. 



f. 1. — TF. t.S.f. 41. Oblong subrhombic, very tliick, pale fulvous, 



with strong concentric wrinkles, gaping and obliquely subtruncated 



at both extremities, ventrally incurved. 4^ . . 8|. — Mediterranean. 



P. Zelanica. Quoy. Ai^t. t. 83. /. 7, 8, 9. Regularly oval- 



ohlong, 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 Lutrarice. 



P. Australis. Sow. G.f. 2.— Reeve, t. 27. f. 2. Ovate-ob- 

 long, transverse, roughly wrinkled concentrically, rather bi'oad at 

 the anterior end ; all but truncated obliquely at the shorter poste- 

 rior extremity. 



P. Arctica. Gould Mas. p. ^7. f. 27. — Glycimeris A. Lam. 

 — Oblong, somewhat cylindrical, strong, anterior side twice as long 

 as the rounded posterior and truncated ; widely gaping at both ends, 

 ti-aversed by two radiating wavelike ridges which divide the surface 

 into three portions. If . . 2^. — Newfoundland. Nottmlike Mya 

 Truncata.^ 



GLYCIMERIS. 



Transverse, gaping widely at each extrernity ; 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. Candida. Sow. G. — Reeve, t. 32. Oblong, white, the 

 central portion covered with decussated divaricating striee, which 

 proceed from the umbo downwards. 2f . . 1^. 



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. 



