124 CARBONIFEROUS LAMELLIBRANCHIATA. 



Since writing the above I have received Dr. Tornquist's work, ' Das fossil- 

 fiihrende Untercarbon in den Siidvogesen,' 1896, in which he describes a new 

 species of Myalina — M. tenuisulcata — p. 66, pi. xvii, fig. 10, which is very similar 

 to the above ; and, if the two forms are shown to be identical, Dr. Tornquist's 

 specific name must take the place of compressa. 



Myalina lamellosa, de Koninck, 1842. Plate IV, figs. 13, 14, 14 a, 14 6. 



Myalina lamellosa, de Koninck, 1842. Anim. foss. terrain Carbonif. Belgique, 



p. 126, pi. iii, fig. 6. 



— virgula, de Koninck, 1842. Ibid., p. 127, pi. vi, fig. 3. 



— lamellosa, Bronn, 1848. Nomenclat. Palseontolog., p. 763. 



— virgula, Bronn, 1848. Ibid., p. 763. 



Mttiltjs lamellosa, d'Orb., 1850. Prodr. Paleontol., vol. i, p. 135. 



Avicula virgula, d'Orbigny, 1850. Ibid., p. 138. 



Myalina lamellosa, Morris, 1854. Catal. Brifc. Foss., p. 214. 



— — Armstrong and Young, 1876. Catal. Western Scottish Fossils, 



p. 54. 



— — Bigsby, 1878. Thesaur. Devonico-carbonif'erus, p. 309. 



— virgula, Bigsby, 1878. Ibid., p. 309. 

 Mtetilus virgula, Bigsby, 1878. Ibid., p. 311. 



Myalina lamellosa, de Koninck, 1885. Ann. Musee.Koy. d'Hist.Nat. deBelgique, 



torn, xi, p. 169, pi. xxix, fig. 11. 



— — Etheridge, 1888. Brit. Foss., part i, Palseoz., p. 286. 



Specific Characters. — Shell of moderate size and variable shape; obliquely 

 elongated and roughly triangular ; thickened anteriorly, compressed and subalate 

 posteriorly. The anterior border is straight, sloping downwards and backwards, 

 and the valve is expanded, so that the shell has a well-marked anterior surface. 

 The inferior border is bluntly rounded. The posterior border is thin and truncate 

 from above downward, making an obtuse angle with the posterior end of the 

 hinge-line, which is straight and short. The umbones are small, pointed, and 

 terminal. Extending backwards and downwards to the junction of the anterior 

 and superior borders is a well-marked oblique gibbosity, with a rapid slope 

 anteriorly, but posteriorly to it the shell is gradually compressed and expanded. 



Interior. — The hinge-plate is expanded and longitudinally striated. Mantle- 

 line and muscle-scars normal in arrangement. 



Exterior. — The surface is covered with a large number of moderately fine 

 concentric lamellae, more or less imbricated. 



