134 CARBONIFEROUS LAMELLIBKANCHIATA. 



excess of the concentric markings. Even where P. squamifer possesses radiation 

 on the interlamellar surfaces this is very large, and only found on the posterior 

 slope. It is of interest that the two species occur together in the same bed of 

 limestone on Trey cliffs, Castleton. 



As far as I can ascertain, this species has not hitherto been described from 

 Great Britain. I am permitted by the kindness of the possessors to figure four 

 specimens (PI. IX, figs. 14 — 17) from the cabinet of Mr. Joseph Wright, from 

 Little Island, co. Cork, and another example (PI. IX, fig. 13), from the cabinet 

 of Mr. W. F. Holroyd. 



The English example (PI. IX, fig. 13) is a much coarser shell, with the concen- 

 tric lamella? more conspicuously raised than obtains in the Irish examples ; but the 

 shape and details of the ornament are precisely identical, and the difference is due 

 probably entirely to environment, the comparative dimensions being the same in 

 both the Castleton and the Little Island shell. 



The Irish series fortunately show the species at various stages of growth, and 

 it is to be remarked that the typical ornament is present even in the smallest 

 example, PI. IX, fig. 17. This specimen is the most perfect of the series, and I 

 have had enlarged drawings, as well as those of natural size, made of it to show 

 the view from above, fig. 17 c, and the ornament of the valves, fig. 17 a. 



Parallelodon bistriatus, PortlocJc, sp., 1843. Plate IX, figs. 5 — 12. 



Cypricardia squamifera, de Koninck, 1842. Anim. Foss. Carbonif. Belgique, 



p. 92, pi. iii, fig. 11. 

 Pullastea ? bistriata, Portloclc, 1843. Geol. Londonderry, p. 440, pi. xxxvi, 



fig. 13. 



— — M'Coy, 1844. Carb. Foss. Ireland, p. 54, pi. xiii, fig. 22. 



— — Bronn, 1848. Nomencl. Palaeont., p. 1059. 



Omalia bistriata, de Byckholt, 1853. Melanges Paleont., part 2, p. 75, pi. xiv, 



figs. 19, 20. 

 Pulltjstra bistriata, Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 222. 



— — Griffith, 1860. Journ. Geol. Soc. Dublin, vol. viii. 



— — Bigsby, 1878. Thesaurus Devonico-Carboniferus, p. 311. 

 Omalia bistriata, Idem. Ibid., p. 311. 



Pullastea bistriata, Etheridge, 1885. Brit. Foss., part 1, Palaeozoic, p. 289. 

 Parallelodon bistriatus, de Koninck, 1885. Annal. Mus. Hist. Nat. Belgique, 



vol. xi, p. 142, pi. xxi, figs. 7 — 9 ; 



pi. xxvi, figs. 13, 14. 



Specific Characters. — Shell equivalve, small, clavate, somewhat compressed, 

 almost pointed posteriorly, somewhat oblique. The anterior end is very short, 

 but produced downwards, so that it has the largest dorso-ventral diameter of the 



