STROPHOMENID^. 323 



and by this character, as well as by the very few external principal radii, it is easily 

 separable from Lept. transversalis. This species will, however, demand further research, 

 and better material should be sought for. 



Position and Locality/. In ' Siluria ' Leptana quinquecostata is said to be limited to the 

 Caradoc or Bala period ; but it has been obtained by Prof. Ramsay in the Upper Llandeilo 

 of Gam, and south side of Arenig, and by Mr. Hughes in the Lower Llandovery ; and 

 also in the Upper Llandovery by Mr. Salter. 



From the Caradoc it has been found west of Bala Lake, in Merionethshire. In the 

 Bala Schists of Cefn Rhyddan, Llandovery, South Wales; in the Bala Schists of 

 Mathyrafal, Meifod, JMontgomeryshire ; Bala Schists of Goleugoed and Penlan, Llando- 

 very, South Wales ; of Pen-y-Craig, Llangynyw, Montgomeryshire, &c. ; of Moelydd 

 and Tyisaf Llangedwyn. Mr. Hughes has found it also near Sedberg, in Yorkshire. 

 It is stated at p. 260 of the third vol. of the ' Mem. of the Geol. Survey ' to have been 

 obtained at Llandovery in Upper Llandovery rocks. 



In Scotland it is stated by M'Coy to be not uncommon in the green trappean 

 sandstone of Glenwhapple, and at Ardwell, near Girvan, in Ayrshire. I have also seen it 

 from the Caradoc Limestone of Craig-head Quarry in the same neighbourhood ; also 

 from Colmonel, on the Stinchar. 



In Ireland it is stated to occur in the Sandstone of Cooling Cong, County Galway ; 

 also in the Limestone of the Chair of Kildare, &c. 



Abroad it is mentioned as being found in Russia by Messrs. D'Eichwald and Schmidt. 



Lept^na sERiCEA, Sow. PI. XLVIII, figs. 10 — 19. 



Lept^na SERICEA, J. de C. Sow. Sil. Syst., pi. xix, figs. 1, 2, 1839. 

 OuTHis — D'Eichwald. Sil. Syst. in Esthl., p. 157, 1840. 



— — Portldck. Geol. Londonderry, p. 450, pi. xxxii, figs. 23, 24, 



1843. 

 Lept^na — De Verneuil. Geol. Russia, vol. ii, p. 227, pi. xv, fig. 1, 1845. 

 _ _ M'Coy. Sil. Fobs. Ireland, p. 27, 1846. 



— — Barrande. Sil. Bracb. Bohmen ; Naturw. Abhandl., vol. ii, p. 71, 



pi. xxi, fig. 18, 1847. 



— — Sail. Pal. New York, vol. i, pp. 1 10 and 287, 1847 ; vol. ii, p. 59. 



— — Phillips and Salter. Mem. Geol. Survey, vol. ii, p. 285, 1848. 



— — M'Coy. Brit. Pal. Foss., p. 237, 1852. 



— — Salter. Siluria, 3rd ed., p. 210, fig. 6, and pi. v. fig. 14, 1859. 



— — D'Hichwald. Lethaea Rossica, vol. i, p. 870, 1859. 



— — Salter. Mem. Geol. Survey, vol. iii, p. 266, 1866. 



Sj)ec. Char. Transversely semicircular, longer than wide ; hinge-line nearly as wide 

 as, or shghtly exceeding, the width of the shell. Cardinal extremities angular, but 



