BIVALVIA. 99 
It may be further described as being furnished with two cardinal teeth in the left 
valve, the anterior one is somewhat thin, sharp, and angular, sloping towards the muscle 
mark on that side, the other one on the posterior side of the umbo is thick, strong, and 
rugose, with a sharp, linear, lateral tooth, nearly parallel to the dorsal margin, or liga- 
mental fulcrum: the right valve has one large cardinal tooth divided in the middle, this 
fits into a depression in the left valve of a corresponding form, and parallel to the margin 
is an elongated, sharp, and elevated, lateral tooth ; the muscle marks are deeply im- 
pressed, more especially the anterior one, this is rugose and subquadrangular, and is 
bipartite or has a smaller one adjoining, more within the shell; the posterior one, 
placed at the extreme edge of the ligament, is slightly ovate, with the mantle mark 
parallel to the margin of the shell, connecting the adductors ; the posterior is obtusely 
angular, and the shell on that side is somewhat compressed or less tumid than at the 
anterior: the surface of the shell is roughened by irregular and prominent lines 
of growth; on many of the individuals there are the remains of the epidermis, and 
in most instances the specimens have the ligament entire, with the valves in their 
natural position. 
Several valves in my Cabinet have specimens of Sa/anus adhering to them, 
showing the proximity of the Sea at one time to this Deposit, or perhaps the re- 
occupation by salt-water of the locality once filled with fresh-water and its inhabitants. 
This species has now an extensive Geographical range, being found in the North 
of France, and in the fresh-waters of the Island of Sicily; and Lea, in his ‘ Observations 
on the Genus Unio,’ vol. i, p. 201, says “the shell found in the Euphrates, near 
Bagdad, is only a variety of this species,” and he records it also as the opinion of the 
Baron de Ferussac. I have never seen this shell. 
2. Unio tumipvus, Retzius. Tab. XI, fig. 13. 
Unio tumipus. Retz. Nova. Gen. Test., p. 17, 1788. 
_ — Pfeiff. Land und Sussw. Moll., pt. ii, p. 34, pl. 7, figs. 2, 3, and pl. 8, 
figs. 1, 2. 
— — Rossm. Icon. Land und Sussw. Moll., pt. i, p. 117, pl. 8, fig. 70; 
pt. ii, p. 27, pl. 14, figs. 262—4; pl. 40, fig. 542; pl. 60, 
figs. 772—778. 
— _— Gray. Man. Land and F. W. Shells, p. 297, pl. 2, fig. 13, 1844. 
— — Forb. and Hanl. Hist. Brit. Moll., vol. ii, p. 140, pl. 40, fig. 1, 1849. 
Mya ovauts. Mont. Test. Brit., p. 34, 1803. 
— pppressa. Don. Brit. Shells, vol. ii, t. 101, 1802. 
— ovata. Don. Brit. Shells, vol. iv, t. 122, 1803. 
Mysca ovata. Turt. Brit. Biv., p. 246, 1822. 
— —_ Swains. Malac., p. 277, fig. 56, 1840. 
— soups. Turt. Brit. Biv., p. 246, pl. 16, fig. 2, 1822. 
Unto picrorum. Brown. Illust. Brit. Conch., pl. 26, fig. 2, 1827. 
— ovauts. Sowerby. Genera of Shells, No. 16, Unto, fig. 1. 
— — Brown. Must. Brit. Conch., 2d ed., pl. 31, figs. 1—4. 
—- rostrata? Desh. 2d ed. Lam., p. 540, t. vi, 1835. 
