274 CARBONIFEROUS LAMELLIBRANCHIATA. 



division of the Belgian Carboniferous series, and claims that it is characteristic of 

 this division in Ireland ; but, unfortunately for this view, it occurs with a fauna of 

 Visean facies at St. Dooghlas, and I have collected a specimen (fig. 7, PI. XXIII) 

 from the uppermost beds of the Carboniferous Limestone of Derbyshire. 



Cardiomoepha Egertoni, M'Coy, sp., 1844. Plate XXIV, figs. 1 and 2 ; 



Plate XXV, figs. 1—4. 



Cyprina Egertoni, M'Coy, 1844. Synops. Carb. Foss. Ireland, p. 55, pi. x, 



fig. 9. 

 Cardium orbiculabe, M'Coi/, 1844. Ibid., p. 56, pi. xii, fig. 7. 

 Mactra incrassata, M'Coy, 1844. Ibid., p. 52, pi. xix, fig. 8. 

 Cyprina Egertoni, d'Orbigny, 1850. Prodrome de paleontol., p. 133. 



— — Morris, 1854. Catal. Brit. Foss., p. 199. 



Mactra incrassata, Morris, 1851. Ibid., p. 209. 

 Cardium orbiculare, vel Edmondia, Morris, 1854. Ibid., p. 193. 

 Edmondia Egertoni, M'Coy, 1855. Brit. Pal. Foss., p. 500. 

 Cyprina Egertoni, Griffith, 1860. Journ. Geol. Soc. Dublin, vol. ix, p. 91. 

 Non Edmondia Egertoni, Young and Armstrong, 1S71. Trans. G-eol. Soc. Glasg., 



vol. iii, Supplement, p. 51. 

 — — — — 1876. Cat. West-Scott. Foss., p. 53. 



Cardiomoepha Egertoni, Bigsby, 1878. Thesaurus Devonico-carbonif., p. 301. 



— — Etheridge, 1885. Brit. Foss., vol. i, Palaeozoic, p. 2S0. 



Mactra incrassata, Etheridge, 1SS5. Ibid., p. 285. 

 • Cardium orbiculare, Etheridge, 1885. Ibid., p. 281. 

 Paciiydomus Egertoni, de Koninch, 1885. Ann. Mus. Roy. Hist. Nat., vol. xi, 



p. 25, pi. v, fig. 4; pi. vi, figs. 3, 

 4, 15, 16. 

 depressus, de Koninch, 18S5. Ibid., p. 25, pi. iv, figs. 1, 2. 

 — MacCoyi, de Koninch, 18S5. Ibid., p. 26, pi. v, figs. 11, 12. 



Edmondia orbiculata, de Koninch, 1885. Ibid., p. 40, pi. iii, fig. 12 ; pi. vii, figs. 



1, 2, 15, 16. 



Specific Characters. — Shell large, triangular orbicular, only slightly inequivalve, 

 regularly but only moderately convex. The anterior end is large, compressed, and 

 narrowed in the dorso-ventral diameter. Its border is more or less semicircularly 

 rounded, and passes with a regular sweep into the hinge-line above and the 

 ventral border below. The latter is rounded, the segment of a larger circle than 

 that of the anterior edge. The posterior border is also rounded ; but above there 

 is an approach towards truncation, the postero-superior angle being obscurely 

 obtuse. The hinge-line is gently arched and extended ; the posterior portion being 

 almost straight and elevated. The umbones are obtuse, tumid, twisted inwards 

 and forwards, and only slightly curved on themselves, slightly elevated above the 



