MYTILOMORPHA RHOMBEA. 341 



Ctpricardia bipaetita, de Koninck, 1842. Desc. aniin. foss. de Belg., p. 94, 



pi. i, figs. 15 a — c. 



— rhombea, Morris, 1843. Cat. Brit. Foss., 1st edit., p. 86. 



— glabrata, Morris, 1843. Ibid., p. 85. 



— rhombea, M'Coy, 1844. Synopsis Carb. Toss. Ireland, p. 61. 



— — de Verneuil, 1845. Geo]. Bussia in Europe, &c, vol. ii, 



p. 304, pi. xix, fig. 15. 



— — Bronn, 1848. Nomenclat. Palseontol., p. 386. 



— glabrata, Bronn, 1848. Ibid., p. 386. 



rhombea, Brown, 1849. Atlas Foss. Conch., pi. lxxxi, fig. 3. 



— glabrata, Broivn, 1849. Ibid., pi. lxxxi, fig. 10. 

 rhombea, d'Orbigny, 1850. Prodrome de paleontol., p. 130. 



Solenopsis scapha, de Ryckholt, 1S53. Melanges paleontol., p. 61, pi. xiv, 



figs. 5, 6. 

 Ctpricardia rhombea, Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 198. 



— glabrata, Morris, 1854. Ibid., p. 19S. 



Non — rhombea, Eichivaid, 1860. Lethaea Rossica, vol. i, p. 1014. 



— — — Young and Armstrong, 187 '1. Trans. Geol. Soc. Glasgow, 



vol. iii, Supplement, p. 51. 



— — glabrata, Young and Armstrong, 1871. Ibid., p. 50. 



— — rhombea, Young, Armstrong, and Robertson, 1876. Cat. West 



Scotl. Foss., p. 53. 



— — glabrata, Young, Armstrong, and Robertson, 1876. Ibid., p. 53. 



— . rhombea, Bigsby, 1878. Thesaurus Devonico-Carbonif'erus, p. 305. 



— glabrata, Bigsby, 1878. Ibid., p. 305. 



Sanguinolites rhombetts, de Koninck, 1885. Ann. Mus. d'Hist. Nat. de Belgique,. 



torn, xi, p. 68, pi. xv, fig. 28. 



— BiPARTiTtrs, de Koninck, 1885. Ibid., p. 69, pi. xv, fig. 27. 



— cuneattjs, de Koninck, 1885. Ibid., p. 71, pi. xvi, figs. 14, 15. 



— scapha, de Koninck, 1885. Ibid., p. 70, pi. xv, fig. 38. 

 Cypricardia rhombea, Etlieridge, 1888. Brit. Foss., pt. 1, Palaeozoic, p. 282. 



— glabrata, Etlieridge, 1888. Ibid., p. 282. 



Specific Characters. — Shell above medium size, very inequilateral, transversely 

 and somewhat irregularly trapezoidal, narrowed anteriorly, expanded pos- 

 teriorly, strongly carinate. The anterior end is very small and narrow, projecting 

 forwards much below the level of the rest of the valve, its border an irregular 

 ellipse passing into the long and straight ventral margin, which forms the longest 

 diameter of the shell, and meets the posterior margin at a rounded right angle. 

 The posterior border is truncate from above downwards, and is almost vertical, 

 very slightly curved, meeting the hinge-line at a rounded angle, almost a right 

 angle. The hinge-line is arched in front but produced, straight and elevated 

 behind. The umbones are comparatively small, angular, incurved and directed 

 forwards, so that they appear produced over the small and low anterior part, but 

 do not form the most anterior part of the valve. Passing obliquely downwards 



44 



