138 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



3. Naiaditrs carinata, Sowerby, 1836-40. Plate XVIII, figs. 1 — 16. 



Modiola carinata, Sowerby. Trans. Geol. Soc, ser. 2, vol. v, pt. 3, pi. xxxix, 



fig. 15, 1836-40. 

 No name. R. Garner. Nat. Hist, of the County of Stafford, pi. e, fig. 19. 

 Modiola carinata, Brown. Foss. Condi., p. 175, pi. lxi***, figs. 19,20, 1849. 

 Mytiltjs Omaliusiana, de Ryckholt. Melanges Paleontologiques, p. 144, pi. viii, 



figs. 22, 23, 1850. 

 — Marije (diyisus), de Ryckholt. Ibid., p. 142, pi. viii, figs. 15, 16. 

 Dreissenia Feldmani (pars), Ludwig. Palaeontograpbica, Bd. viii, p. 188, pi. lxxi, 



figs. 3, 4, 1859-60. 

 — dilatata (pars), Ludwig. Ibid., p. 189, pi. lxxi, figs. 5 and 6. 



Myalina carinata, Salter. Geol. Surv. Mern., " Iron Ores of South Wales," 



p. 228, pi. ii, fig. 15, 1861. 

 Anthracomya carinata, Hull. Coalfields of Great Britain, 4th edit., facing 



p. 38, fig. 3, 1873 and 1881. 

 Myalina carinata, Barrois. Becherches sur les terrains anciens des Asturies et 



de la Gallice, p. 336, pi. xvi, figs. 12 a, b, 1882. 

 Anthracoptera carinata, JVard. Trans. North Staff. Inst. Min. and Mech. 



Engin., vol. x, p. 129, pi. i, fig. 9, 1890. 



— — Hind. Quart. Jouru. Geol. Soc, vol. xlix, p. 253, 



plvii, figs. 2, 2a, 10, 10a, 11, 12, 12a, 1893. 



— tumida (pars), Hind. Ibid., pi. vii, figs. 13, 13 a, 14. 



Specific Characters. — Shell produced obliquely downwards, rbomboidal, and 

 gibbose. The anterior lobe is comparatively larger than in other species. The 

 anterior and posterior margins are almost parallel, the anterior being straight and 

 slightly notched about its centre for the byssus, the posterior for the most part 

 straight, but slightly convex below at the posterior inferior angle, and may be 

 either straight or convex above, according as the angle formed by the junction of 

 the superior and posterior borders is a right angle or greater than a right angle. 

 The inferior margin is short and rounded, almost semicircular. The hinge- 

 line is straight, about as long as any diameter of the shell parallel to it. The 

 umbones are anterior, not quite terminal. They at first lie parallel to the hinge- 

 line, but then become twisted outwards and are continuous with a sharp ridge 

 which crowns a broad oblique gibbosity very much more pronounced in the left 

 valve. This swelling and ridge pass downwards and backwards and become lost 

 on the surface of the shell near the posterior inferior angle, the line of the 

 ridge forming with the hinge-line an angle of l"> in most cases. The anterior 

 part of the shell forms a small projecting lobe, and is swollen above, but becomes 

 compressed obliquely parallel to and in front of the ridge. The posterior part of 

 the shell is much compressed, especially above. 



