328 BRITISH SILURIAN BRACHIOPODA. 



in our plate, which have been carefully selected with that view. The interior is also 

 very peculiar, but is rarely found, except in the condition of internal casts. In some 

 rocks, such as the olive-coloured Caradoc Schists of Cynwyd, near Corwen, in Merioneth- 

 shire, Mr. Parrott found casts of this s})ecies strangely distorted by cleavage ; some 

 examples having been so much lengthened as to present seventeen lines in length by 

 only six in breadth ; whilst in all probability the shell itself was originally not more than 

 eight or nine lines in length at the utmost. 



In external shape, as well as in the internal characters of the dorsal valve, L. 

 iemiicincta bears a great resemblance to Leptana obloncja of Russia {Pledambonites ovata 

 and oblonga. Pander, 1830) ; but this last is stated by M. de Verneuil to be very finely 

 and longitudinally striated, and not concentrically, as in the shell under description ; but 

 the Gothland Lept. (enigma (De Verneuil) so closely resembles Lept, tenuicincta that we 

 have considered it synonymous. 



Position and Locality. L. tenuicincta is stated in ' Siluria ' to range through the 

 Llandeilo and Caradoc series. Prom the Upper Llandeilo Prof. Ramsay and Salter 

 obtained it at Pron-oleu, three miles east of Llangefni, in North Wales ; and in the 

 Caradoc south of Cerrig-y-Druidion, in Denbighshire; Llanfyllin and Meifod, Mont- 

 gomeryshire ; west and north of Bala Lake (especially Rhiwlas), in Merionethshire. 

 Prof. M'Coy quotes it from olive Bala Schists at Cefn Grugos, west of Llanfyllin, Mont- 

 gomeryshire. I have seen it also from Lledfron and Rhosfawr, near Llanfyllin ; Sholes 

 Hook, Haverfordwest ; and Keisley, in Westmoreland. 



In Scotland it occurs at Penwhapple-glen, Knockgerran, and several other localities 

 near Girvan, in Ayrshire. 



In Ireland at the Chair of Kildare. At Tyrone very fine internal casts of the dorsal 

 valve were found by Mr. Wyatt-Edgell, and of these figures will be found in our plate. 



LePT^NA (?) L^VIGATA, Sow. PL XLIX, figs. 1 — 12. 



LEPTiENA LiEviGATA, J. de C. Sow. Sil. Syst., pi. xiii, fig. 3, 1839. 



— — Dav. London Geol. Journ., vol. i, p. 59, pi. xii, fig. 30, 1847. 



— LEPiSMA, var. MINOH, Phillips and Salter. Mem. Geol. Surv., vol. ii, p. 



284, pi. xxvi, figs. 3, 4, 1848. 



— L^viGATA, 3I'Coij. Brit. Pal. Foss., p. 235, 1852. 



— — Salter. Siluria, 3rd ed., pi. xx, fig. 15, 1859. 



Spec. Char. Shell small, semicircular, widest at the hinge-line, cardinal extremities 

 prolonged into acute-angled mucronate wings. Ventral valve very gently convex or 

 flattened posteriorly, most convex at the beak and near the margin. Area narrow ; 

 fissure arched over with a pseudo-deltidium ; beak scarcely projecting, with sometimes 



