366 CARBONIFEROUS LAMELLIBRANCHIATA. 



according to the character of the ornament of the surface of the shell, in precisely 

 the same manner as obtains in the genus EdinoiuUa. There is a well-marked 

 group characterised by concentric ridges and sulcations, of \Yhich the type is 

 S. angustatus, and a smoother group of which the type is aS'. tricostatus. The 

 latter group has all the external characters of Plenrophorus, but I cannot 

 satisfy myself that they possess the characteristic hinge of this genus. The 

 genus Gyprlcardella similarly contains two groups, according as their surface is 

 ribbed or smooth. 



Sanguinolites angqstatus, Phillips, sp. Plate XL, figs. 1 — 6. 



Sanguinolaria ? ANOUSTATA, PhllUps, 1836. Geol. Yorks., pt. 2, p. 208, pi. v, 



fig. 2. 



— — Morris, 18J-3. Cat. Brit. Foss., 1st edit., p. 100. 

 Sanguikolites angustatus, 21' Coy, 18-ii. Synops. Carb. Foss. Ireland, p. 48. 



— Discoiis, 3PCoy, IS-IJ-. Ibid., p. 49, pi. viii, fig. 4. 

 Sanguinolaria angustata, Brown, 1849. Illust. Foss. Concb., p. 219, pi. xc, 



fig. 12. 

 Lyonsia angustata, cVOrhir/ny, 1850. Prodrome Paleont., vol. i, p. 128. 

 Sanguinolites angustatus, Morris, 1854. Cat. Brit. Foss., 2ud edit., p. 223. 



— DiscoRS, Morris, 1854. Ibid., p. 223. 



— — Griffith, 1860. Journ. Geol. Soc. Dublin, vol. ix, p. 35. 

 ? — — Young and Armstrunf/jl^l 1. Trans. Geol. Soc. Glasgow, 



vol. iii, Supp]ement,p. 53. 

 Compare Allorisma costata, Meek and Worthen, 1873. Geol. Surv. Illinois, vol. v, 



p. 585. 

 ? Sanguinolites discors, Young, Armstrong, and liolertson, 1S7G. Cat. W. Scott. 



Foss., p. 55. 



— angustatus, Bigshy, 1878. Thesaurus Devonico-Carboniferus, 



p. 311. 



— DISCORS, de Koninch, 1885. Ann. Mus. Eoj. Hist. Nat. Belgique, 



vol. xi, p. 60, pi. XV, fig. 33. 



— angustatus, Etheridge, 1888. Brit. ross.,pt. 1, Palaeozoic, p. 289. 



— DISCORS, Etheridge, 1888. Ibid., p. 289. 



Specific Characters. — Shell of moderate size, transversely oblong, very in- 

 equilateral, tumid. The anterior end is short and gently convex, narrowed, its 

 margin almost elHptical. The inferior border is gently and regularly convex, the 

 arc of a very large circle. The posterior border is blunt and truncate, very 

 slightly convex, but more so above, where it meets the superior border at an 

 obtuse angle. The postero-inferior angle is a rounded right angle. The hinge- 

 line is long and almost straight, but appears to be curved, so that its arc is 



