BIVALVIA. 59 
Dreissena Brarpul, Mayas St. Fond. Tab. XII, fig. 8, a—e. 
Movie. Faw. St. Fond. Ann. du Mus,, t. vill, t. 58, figs. 11, 12. 
Myritus Brarpit. Brongn. Terr. calc. Trap. du Vincentin, t. 6, fig. 14, 1823. 
_— — Goldf. Petr. Germ., vol. ii, p. 271, t. 129, fig. 10. 
— — J. Sowerby. Min. Conch., t. 532, fig. 2, 1826. 
oo Bronn. Leth. Geog., t. ii, p. 923, pl. 39, fig. 10, 1836. 
— — Nyst. Rech. Coq. foss. Hoess. et Kl. spaw., p. 13, No. 22, 1836. 
7 _ var. 6? Basterot. Bordeaux Foss., No. 2, p. 78. 
?— Basrerorm. Dyardin. Tr. Géol. Soc. Fr., vol ii, p. 269. 
? 
? 
‘—  acutirostris. Goldf. Petr. Germ., t. v, pl. 129, fig. 11, p. 272. 
?—  spatTHuLatus. Id. - - fig. 12. 
Coneeria Basreroti? Desh. Conch., 650, t. 37, figs. 15, 16. 
DretssenA Brarpu. Morris. Catal. Brit. Foss., p. 202, 1854. 
— —- Pictet. Traité de Paleont., pl. 81, fig. 11. 
— Basrerorr. Nyst. Conch. Foss. Belg., p. 265, pl. 20, fig. 7 a—e. 
— Sowrrsyr. D’Orbigny. Prod. de Palzont., t. 11, p. 425, No. 1637, 1850. 
Spec. Char. D. testa ovata vel elongato-cuneatd ; levigatd, obtusé carinatd ; umboni- 
bus acutis ; septo cochleato. 
Shell ovate or elongately wedge-shaped, smooth, and obtusely carinated ; beaks sharp 
and pointed ; septum concave. 
Length, ths of an inch. 
Localities. ordwell, Headon Hill (Forées). 
Belgium, Limbourg (Wys?), Weisenau, Env. de Mayence (4. Brongniart). 
This little shell is abundant in the fine sandy stratum at Hordwell which has yielded 
so many beautiful vertebrate fossils. Upwards of a hundred specimens were obtained by 
myself, congregated in and around the upper jaw of <Ad/igator Hantoniensis. It is pos- 
sible that the decomposition of the flesh of the dead reptile may have rendered the water 
at that place favorable to the multiplication of the mussel. I found the shell elsewhere, 
but in no other place in so great abundance. 
My specimens are variable in outline; the proportions in some are from 23 to 1, while 
in others they are not more than 13 to 1, the more elongated being also the more 
tumid. The umbo is a little inflected, and in some specimens there is a flattening on 
the siphonal region. The shelf is of a moderate size, and is not entirely occupied by the 
muscle, the mark of which is indented on it, and is of a roundedly oval shape. The 
cartilaginous portion of the connexus extended about two fifths of the longest diameter of 
the shell, and, like that of M/ytilus, it was nearly covered by the dorsal edge. Many 
specimens of a small Serpula (¢enuis) were found with this mussel in association with 
numerous specimens of Limnez, Cyrene, &c., and in one of the specimens there is 
what appears to be the arenaceous case of a Sadella (fig. 3a). We have, thus, 
supposed marine animals living in fresh water with Limnee, or we have the supposed 
