SPIRIFERA. 59 



On the Continent it has been discovered at Tournay, in Belgium, by Professor L. de 

 Koninck, and where the shell attains rather larger dimensions than is common to our 

 British individuals. 



Although the external surface of all the specimens of Sp. Urii appeared smooth, by the 

 help of the lens I was able to discern in some examples the broken base of numerous 

 spinules, which must have covered its surface lin the perfect condition. 



SpiRiFERA Carlukensis, Dttvidson. PI. XHI, fig. 14. 



Spec. Char. Shell minute, nearly circular, and smooth ; valves almost equally deep. 

 Dorsal valve regularly convex, most so at the umbone. Ventral valve convex, with a 

 narrow mesial depression or furrow commencing at a short distance from the extremity of 

 the beak and extending to the front, where it indents the margin of the opposite valve. 

 Beak small, pointed, and but slightly incurved ; hinge hne much shorter than the greatest 

 width of the shell, with its cardinal angles rounded • area small, triangular, with a 

 comparatively large fissure. 



Length 2, width 2|, depth \\ lines. 



Obs. This little shell, which I believe to be new, was discovered in the Carboniferous 

 beds of Hill Head, Carluke parish, Scotland, by the same friend to whom I am indebted 

 for so much information relative to the Lanarkshire species. It is easily distinguished 

 from Sp. Urii, Avith which it is associated by the almost equal convexity of its valves, and 

 by the absence of a mesial groove on the dorsal valve. The beak is likewise much smaller, 

 more acute, and less incurved. Sp. Carlukensis does not appear to have been a very 

 common shell in its locality, where a hundred or more of Sp. Urii may be collected for one 

 of the species under description, nor am I acquainted with the shell from any other British 

 or foreign locality. 



Spirifera glabra, Martin. PI. XI, figs. 1—9; PI. XII, figs. 1—5, 11, 12. 



CoNCBYLiOLiTHUS ANOMiTBS GLABER, Martin. Pctrif. Derb., pi. xlviii, figs. 9, 10, 1809. 

 Spirifer GLABER, Soioerby . Mill. Con., vol. iii, p. 123, pi. cclxix, fig. 1, May, 1820. 



— OBTUSUS, Sowerby. Ibid., p. 124, pi. cclxix, fig. 2. 



— 0BLATU8, Sowerby, Ibid., p. 123, pi. cclxviii. 



— GLABER, Davreux. Const. Geogn. de la Province de Liege, p. 272, pi. vii, fig. 1, 



1831. 

 Trigonotreta oblata, Bronn. Loth. Geogn., i, p. 81, pi. ii, fig. 16, 1836. 

 SpiairERA GLABRA, Phillips. Geol. of Yorksh., vol. ii, p. 219, pi. x, figs. 10 — 12, 1836. 



— LiNGUirERA, Phillips. Ibid., fig. 4. 



— SYMMETRICA, Phillips. Ibid., fig. 13. 



