148 DEVONIAN FAUNA. 



also met with about twenty very similar casts in various collections, which appear 

 to be indistinguishable, and which generally show more or less distinctly such 

 points as the vascular sinuses, the subpentahedral shape, and the marginal fold, 

 which rarely seems to be at all strong. With such unsatisfactory material it is of 

 course difficult in many cases to be sure of specific identity ; for instance, the type 

 of Atrypa oblong a, Sowerby, in the museum of the Geological Society is extremely 

 obscure, and I long hesitated between identifying it with the above specimeus, or 

 with those referred below to Cleiothyris Royssii. Its oblong shape is, I think, 

 evidently only due to distortion, but the character of the fold and the size of the 

 dental sockets agree best with the present shell. Moreover Sowerby describes it 

 as " smooth," as are also our specimens. But while, therefore, we may conclude 

 that it belongs, and consequently gives its name, to the species now under con- 

 sideration, we may note that it is not in itself an exponent of its specific value. 



For some time it seemed to me possible that our shell might belong to Athyris 

 concentrica, von Buch, but having examined some casts from the Lower Devonian 

 of Germany which Mr. Upfield Green informs me belong to that species, I find 

 them to be entirely different and distinct. 



The shape of our shell seems different from any of the various English Carboni- 

 ferous forms of Seminula, 



Sub-genus — Cleiothyris, King, 1850 ; emend., Hall and Clarice, 1894. 



3. Athyris (Cleiothyris) Royssii, .Lerf/e. Plate XVII, figs. 13 — 15a; Plate XVIII, 



figs. 1—5 ; and Plate XX, figs. 1, 2. 



1835. Spirifer de-Kotssii, Leveille. Mem. Soc. Geol. Fr., vol. ii, figs. 18 — 20. 

 1840. Atrtpa hispida, Sowerhy. Geol. Trans., ser. 2, vol. v, pt. 3, pi. liv, 



fig. 4. 

 1840. — decussata, Sowerhy. Ibid., pi. liv, fig. 5. 

 ? 1841. Spikifera decussata, Phillips. Pal. Foss., p. 70, pi. xxviii.figs. 120 b — e. 

 1844. Athyris decussata, M'Coy. Syu. Carb. Toss. Irel., p. 147. 

 1844. — depressa, 3I l Ooy. Ibid., p. 147, pi. xviii, fig. 7. 



1844. — hispida, IP Coy. Ibid., p. 148. 



1855. — concentrica, IP Coy (pars). Brit. Pal. Foss., p. 378. 

 1861. — Kotssii, Davidson. Brit. Foss. Bracli., vol. ii, pt. 5, p. 84, pi. xviii, 



figs. 1—11. 

 1864. Terebratula elongata?, Davidson. Ibid., vol. iii, p. 8, pi. i, fig. 9. 

 1864. Athtris concentiuca, Davidson (pars). Ibid., vol. iii, p. 14, pi. iii, figs. 



15(?),l7(?),24(?)(only). 

 1864. — sp., Davidson. Ibid., pi. iv, fig?. 1 — 3. 



