BIVALVIA. 283 



In the living state it has been only obtained in deep water. 



A small obtuse tooth occupies a position immediately beneath the umbo in the 

 living shell, but in the fossil this is merely rudimentary. 



The figure by Middendorff has the siphonal side the larger. 



2. Panopea Faujasii, Menard de la Groyc. Tab. XXVIT, fig. 1, a—f. 



Panopea Faujasii. Men. de la Groye. Ann. du Mus., torn, ix, p. 131, t. 12, 1807. 



— — Dubois de Mont^). Couch. Foss. de Wolhyn. PodoL, p. 51, pi. 4, 



figs. 1—4, 1831. 



Panop.ea Faujasii. Bast. Foss.de Bord., p. 95, 1825. 



— — Bromi. Leth. Geog., p. 973, pi. 37, fig. 6, 1838. 



— — Phil. En. Moll. Sic., vol. i, p. 7, t. 2, fig. 3, 1836. 



— — Goh/f. Pet. Germ., vol. ii, p. 274, t. 159, fig. 1, a — (/. 



— — Valenciennes. Arch, du Mas., vol. i, p. 13, 1839. 



— — /. Sow. Min. Conch., t. G02, figs. 3—5. 



— — Chenu. Conch. Illust., pi. 4, fig. 1, 1. 



— Ipsviciensis. J. Sow. Min. Conch., t. 611, figs. 3, 4. 



— — Valenciennes, hoc. eit. sup., No. 36. 



— REFLEXA. Say. Journ. Acad. Nat. Sc, vol. iv, p. 153, pi. 13, fig. 4, 1S24. 



— — Conrad. Foss. Med. Tert., p. 5, pi. 3, fig. 4, 1838. 



— Americana. Id. Foss. Med. Tert., p. 4, pi. 2. 



— Aldeovandi? Phil. En. Moll. Sic, vol. i, p. 7, t. 1 1, fig. 2. 



— GENTiLis. J. Sow. Min. Conch., vol. vii, t. 610, fig. 1, 1840. 

 Mya Panop.ea? Broc. Couch. Foss. Subap., p. 532, 1814. 



Spec. Char. Testa transversa, ovato-ohhngd, injlatd ; plus minusve incequilaterali ; 

 posfice truncatd et valde Jtiante ; cardine unidentato. 



Shell transverse, ovately oblong, inflated, more or less inequilateral ; posterior side 

 truncated, and gaping widely ; hinge with one tooth. 



Length, 6 inches. Height, 3^ inches. 



Locality. Cor. Crag, Sudbourn, Gedgrave, Ramsholt, 

 Red Crag, Sutton. 



This handsome shell is very abundant as a Crag Fossil, though its great size and 

 comparative thinness has caused it to be somewhat scarce in our Cabinets : at 

 Ramsholt numerous specimens were found with the valves united. It presents a very 

 considerable variation, both in regard to its form, and to the degree of gape on the 

 anterior side, and I am inclined to believe the recent Mediterranean shell called 

 F. Aldrovandi is merely the descendant of our Crag species somewhat altered by 

 local conditions : the Sicilian fossil (specimens of which were obligingly given to me 

 by Madame Power) seems to present some differences ; but they are not, I think, of 

 sufficient importance for specific distinction ; that shell is, in general, rather more 

 inequilateral than the Crag one, but not always so ; and, among my British specimens 



