192 CARBONIFEROUS LAMELLIBRANCHIATA. 



Sowerby ; but this has not the twisted umbones, nor is it so regularly triangular 

 in shape. 



Eichwald's Nucula trivialis (Lethsea Rossica, pi. xxxvii, fig. 15), from the 

 Magnesian Limestone near Kazan, is very similar indeed to the species under 

 discussion ; in fact, I am not able, from a comparison of the figures and description, 

 to point out a single detail of difference. 



There is also a marked similarity to some of the specimens figured as 

 Tellinomya pusilla by de Koninck ('An. Mus. Roy. Hist. Nat. Belgique,' torn, xi, 

 p. 139, pi. xxvi, figs. 34 — 36) ; but other figures purporting to be of the same 

 species, figs. 37 — 40, are very different, and in a note de Koninck doubts if 

 they be of Carboniferous age at all. 



It seems to me quite possible that the blocking of the cartilage cavity with 

 matrix may have prevented this character from being apparent, and that some of 

 the Carboniferous species of the Nuculiclse described as Tellinomya (Ctenodonta) 

 may really belong to Nucula. In some species this cavity is very small, and 

 easily missed when choked with shale, &c. 



The shape of T. pusilla is described as " peu obliquement subovale oblougue." 

 The species was founded on a single valve of doubtful Carboniferous origin, so 

 that I have for cogent reasons hesitated to refer the Scotch specimens to the 

 Belgian species. 



Genus Nuculana, Link, 1807. 



Multiarticulate cockle, Ure, 1793. Nat. Hist. Eutherglen, p. 310. 

 Nucula (pars), Fleming, 1828. Hist. Brit. Anim., p. 403. 



— — Phillips, 1836. Illust. Geol. Yorks., pt. 2, p. 210. 



— ■ — J. de C. Sowerby, 1840. Trans. Geol. Soc, ser. 2, vol. v, Appendix, 



Explanation of pi. xxix. 



— — Morris, 1843. Cat. Brit. Foss., p. 93. 



— — Portlock, 1843. Eep. Geol. Londonderry, p. 439. 



— — M'Coy, 1844. Synops. Carb. Toss. Ireland, p. 69. 



— — Brown, 1849. Iilustr. Foss. Conchology, pp. 184 — 188. 

 Leda (pars), d'Orbiyny, 1850. Prodrome paleont., p. 129. 



Nucula (pars), M'Coy, 1855. Brit. Pal. Foss., p. 511. 



Leda, Stevens, 1858. American Journ. Sci., ser. 2, vol. xxv, p. 261. 



— Sail, 1858. Eep. Geol. Surv. Iowa, vol. i, pt. 2, p. 715. 



— M'Chesney, 1859. Trans. Acad. Sci. Chicago, vol. i (see above, p. 30). 

 Yoldia, Meek and Worthen, 1860. Proc. Acad. Nat. Sci. Philadelphia, p. 457. 

 Nucula, Geinitz, 1861. Carb. u. Dyas in Nebraska, p. 22. 



Leda, Baily, 1862. Mem. Geol. Surv. Ireland, Expl. Sheet 127, p. 9. 



— Winchell, 1862. Proc. Acad. Nat. Sci. Phil., p. 419. 



— — 1863. Ibid., p. 16. 



Ctenodonta, Salter, 1864. Mem. Geol. Surv. Gt. Brit., Geol. Country round 



Oldham, p. 65. 



