454 CARBONIFEROUS LAMELLIBRANCHIATA. 



Akca rosteata, Fleming, 1828. Hist. TBrit. Anim., p. 399. 



PLEUROEHTNcnus ELONGATUS, Phillips, 183G. Geol. Yorks., pt. 2, p. 211, pi. v, 



fig. 28. 

 Cardium EiiONGATUM (pats), GolJfuss, 1841. Petrefact. Germaniao, vol. ii, p. 214, 



pi. cxlii, figs. 2 a, h. 

 — ROSTRATUM, (le Kojiiiick, 1842. Aiiini. Foss. Terr. Carbonif. Belg., p. 87, 



pi. ii, fig. 9. 

 Pledroruykciius ELONGATUS, MorHs, 1843. Cat. Brit. Fos?., Isfc edit., p. 99. 

 Cardium Ouralicum, de Verneuil, 1845. Geol. Kussie, p. 301, pi. xx, fig. 11. 

 Pleuroriitnchus ELONGATUS, Brown, 1849. Illust. Foss. Coacii. Gt. Brit., 



p. 201. 

 CoNOCARDiUM ROSTRATUM, d'Orligtii/, 1850. Prodrome Paleontol., vol. i, p. 132. 



— — Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 195. 



— — irCoy, 1855. Brit. Pal. Foss., p. 517. 



— URALICUM, Eiclnvald, 1860. Letl)a?a Kossica, p. 1022. 

 Cardium elongatum, Ilellmann, 1862. Petrefact. Thuringens, pi. xvii, figs. 



43—45. 

 ? CoNOCARDiuM ALiFORME, liomer, 1876. Lethaea Geoguostica, pi. sliv, fig. 4. 



— ELONGATUM, Biffsbi/, 1878. Tliesaurus Devonico - Carbouiferus, 



p. 303. 



— ROSTRATUM, Bigshi/, 1878. Ibid., p. 303. 



— URALICUM, Bigsby, 1878. Ibid., p. 303. 



— ROSTRATUM, de Koninck, 1885. Ann. Mus. Roy. Hist. Nat. Belg., 



vol. xi, p. 115, pi. XX, figs. 16 — 19. 



— — Elheridge, 1888. Brit. Foss., pt. 1, Paleozoic, p. 281. 



Specific Chdractevfi. — Shell very inequilateral, much elongated anteriorly, sub- 

 fusiform, not so rapidly compressed posteriorly as the majority of the species of 

 the genus, so that a posterior surface is absent. The anterior end is prolonged 

 forwards, and is narrow, subcylindrical, slightly compressed from side to side, 

 truncate, and gaping. The anterior border is very short, and makes a right angle 

 with the extremity of the hinge-line ; it then descends downwards and backwards, 

 passing into the lower border. This is sinuous, convex at first, and soon becomes 

 concave till the lowest point of the valve is reached, marked by the meeting of the 

 ridge or keel with the lower border. From this point the margin becomes bent 

 upwards and backwards at an angle, and becomes continuous with the lower 

 border of the rostrum. The hinge-line is straight, very elongate, continuous 

 behind with the upper border of the rostrum. 



The umbones are small, incurved, pointed, not raised, and are almost equi- 

 distant from the tip of the rostrum behind and the antero-superior angle in front. 

 Passing directly downwards from the umbo to the inferior border is a rounded 

 and very blunt keel, which separates the anterior and posterior parts of the valve. 

 This keel marks the greatest gibbosity of the valve ; and in front of it the valve is 

 gradually compressed from side to side, and narrowed from above downwards into 



