56 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



Localities. — Cockshead Coal-roof, Adderley Green. 



Observations. — Although this form is very distinct from the types of 0. acuta, 

 it is nevertheless connected with it by a well-marked series of intermediate forms, 

 and it is impossible to divide them into distinct species. I have therefore 

 considered the extreme form as a variety of G. acuta, and have figured a series 

 showing the passage of one into the other. All the specimens came from the roof 

 of the Cockshead Coal of Adderley Green. I have chosen a series of adult 

 specimens of about the same stage of growth in order to make it more easy to 

 follow the transition of shape. 



The feature on which Sowerby and M'Coy relied so much for the diagnosis of 

 G. subconstricta is well marked in this variety, — more so, indeed, than in the 

 specific type itself. It is probable that the variability in shape has some connection 

 with the variableness of the hinge-character in G. acuta ; and it will be noted, too, 

 from the figures, that the variety as well as the type-species was subject to erosion 

 of the umbones. A similar variation between an acute and a more quadrate form 

 obtains in G. aquilina. 



4. Caebonicola ovalis (Martin). Plate IV, figs. 18—22 ; Plate V, fig. 38. 



Mta ovalis, Martin. Petrefact. Derb., 1809, pi. xxvii, figs. 1, 2 ; pi. xxviii, fig. 5. 

 Non TJnio unifobmis, Sow. Min. Conch., 1812, p. 84, pi. xxxiii, fig. 4. 

 Syn. — acutus, Dumont. Geol. of Liege, 1832, p. 356. 



— — Davreux. Essai sur la constitution geognostique de Liege, 1833, 



pi. v, figs. 4, 8. 



— cabbonarius, Ooldfuss. Petrefact. Germ., 1834-40, p. 181, pi. cxxxi, 



fig. 19. 



— tellinabius, Ooldfuss. Ibid., p. 180, pi. cxxxi, fig. 16. 



— centralis, Sow. Trans. Geol. Soc, 1840, ser. 2, vol. v, p. 491, pi. xxxix, fig. 13. 



— (no specific name), Bhind. Age of the Earth, 1838, pi. ii, fig. f. 

 Cabdinia ovalis, de Koninck. Carb. Foss. Belg., 1842-4, p. 74, pi. h, fig. 2. 



— ateata, de Koninck. Ibid., p. 75, pi. H, fig. 3. 

 Pachtodon Rhindii, Brown. Ann. Mag. Nat. Hist., vol. xii, 1843, pi. xvi, fig. 2. 

 Unio Rhindii, Broion. Foss. Conch., 1849, p. 187, pi. lxxiii, fig. 5. 

 Non Antheacosia ovalis, Salter. Geol. Surv. Mem., Iron Ores S. Wales, pt. 3, 1861, 



p. 228, pi. ii, fig. 22. 

 — centbalis, Hull. Coal-fields Gt. Britain, 1881, p. 38, pi. ii, fig. 4. 



Non — — Ward. Trans. North-Staff. Inst. Min. and Mech. 



Engineers, vol. x, 1890, pi. i, fig. 16. 

 Non subnucleus, Amalizky. Palseontographica, vol. xxxix, 1892, p. 156, 



pi. xx, figs. 19, 20 (said to resemble 

 Anthracosia ovalis, centralis, and uni- 

 formis). 



