84 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Myacites, Baily, 1881. 
Non Anthracomya, Hull, 1881. 
Anthracosia, Achepol, 1880-83. 
Anodon, Achepol, 1880-83. 
Naiaditis, Barrois, 1882. 
Anthracomya, Ward, 1890. 
— Hind, 1893. 
Generic Characters.—Shell transverse, slightly inequivalve, very inequilateral, 
the anterior end being small and rounded, while the posterior is produced, 
compressed, expanded, and generally truncate. The umbones are small and low, 
situated near the anterior end, very slightly raised above the hinge-line, which is 
straight, long, and with a cardinal and one long posterior lateral tooth in at least 
one species. It has a narrow interior ridge, parallel with the edge, in its posterior 
portion, which leaves a groove in casts. There is present a blunt oblique swelling, 
which arises at the umbones, and expanding as it passes downwards and back- 
wards, becomes lost on the posterior portion of the shell. Parallel and anterior 
to the ridge there is an oblique shallow sulcus, which becomes expanded as it 
approaches the inferior margin. The ligament is small, erect, and external. 
Interior.—Nacreous, smooth ; pallialline simple. Anterior adductor scar deep, 
almost marginal, that of the accessory adductor situated above and posterior 
to it. The posterior adductor scar is shallow and somewhat elongate, generally 
situated on the posterior slope not far from the hinge. 
Surface.—The exterior is ornamented with fine lines of growth and a much 
wrinkled periostracum. 
Observations.—Although Mr. Salter does not mention the fact, figures and 
descriptions of shells belonging to his genus Anthracomya had been given by 
many authors besides Sowerby, to whom alone he refers. As far back as 1836 
Dr..W. C. Williamson described a shell from the Spirorbis Limestone of Pendlebury 
as Unio Phillips (¢ Phil. Mag.,’ vol. ix, p. 3851), which undoubtedly belongs to 
this genus. Continental writers never seem to have recognised Salter’s genus, 
though several species have been described under other generic names; but this 
is no doubt due to the fact that apparently few of these shells are to be obtained 
in the coal-fields of Kurope, if one may judge by the public collections; and, 
although three forms—Anthracomya carbonaria (Bronn), Anthracomya wniformis, 
Goldfuss (generally found to be named, after de Koninck, Goldfussiana), and 
Anthracomya minima, Ludwig (with which the Modiola Carlotta, Rémer, is 
synonymous)—are of frequent occurrence, I do not know of the presence in 
Great Britain of any but the last. 
Mr. Salter himself, when establishing the genus, as is shown by the derivation 
of the name, thought that the shells he was describing had a close affinity to the 
Myas or burrowers of our sea-shores, and referred his new genus to the family 
