84 CARBON ICOLA, ANTHRACOMYA, AND NAIADITES. 



Myacites, Baily, 1S81. 

 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 ; pallial line 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 Unto Phillipsii (' Phil. Mag.,' vol. ix, p. 351), 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 ihw of these shells are to be obtained 

 in the coal-fields of Europe, if one may judge by the public collections ; and, 

 although three forms — Anthracomya carbonaria (Bronn), Anthracomya uniformis, 

 Goldfuss (generally found to be named, after de Koninck, Goldfussiana), and 

 Anthracomya mini ma, Ludwig (with which the Modiola Garlotfa, Romer, is 

 synonymous) — are of frequent occurrence, I do not know of the presence in 

 Greal 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 (tin- sea-shores, and referred his new genus to the family 



