304 



BRITISH SILURIAN BRACHIOPODA. 



progress, divided into seven, ten, or more small ribs ; and these have arranged themselves 

 into clusters with the parent or original rib. The whole surface of each valve is likewise 

 closely intersected by very fine, equidistant, concentric, raised lines. 



Interior not well known. Cardinal process divided into two deviating lobes. 

 Length 10, width 12, depth 1^ lines. 



Obs. This species was found by the Rev. H. G. Day and by Mr. Hughes 

 abundantly in the Lower Silurian Shales (Bala?), at Fairy Gill, Cautley, near Sedberg, in 

 Yorkshire ; and I am indebted to them for the communication of a numerous series of 

 specimens of all ages. The shell varies considerably according to age, especially in 

 the greater or lesser length of its hinge-line, and in the strength and fasciculation of its 

 ribs. In young specimens these last seem to be comparatively stronger, fewer in number, 

 and wider apart, becoming so numerous in the adult condition that about one hundred may 

 be counted round the margin of many of the specimens. The Rev. H. Day supposed it 

 possibly referable to Orthis Hirnanlensis (M'Coy) ; but if so, the distinguished Irish 

 Palseoutologist's description would hardly agree with that here given of the shell under 

 investigation, for our species is certainly a Stroj)homena, and its smaller valve is decidedly 

 concave, and not perfectly flat as that of Orthis Hirnantensis is said to be. The ribbing 

 is also less delicate than in the latter, I will not, however, positively affirm that Mr. 

 Day's first impression was incorrect ; but if correct, 0. Hirnantensis would not be an 

 Orthis, and M'Coy's description would not suit his species. 



Strophomena pecten, Linn. (sp.). PI- XLIII, figs. 1 — 11. 



Lister, Hist. Animal. Aiiglise, pi. ix, fig. 49, 16/8; and Appendix ad Librum iii, de 



Conchitis, &c., 447, i. 1688. 

 Anomia pecten, Linnc. Syst. Nat., editio duodecima, vol. i, pars 2, p. 11.52, 1/67. 

 Terebeatula pecten, Bruffuii're. Encycl. Melbod., pi. ccxliv, fig. 8, 1789. 

 Teuebuatulites pecten, ScJilotlieim. Petrefact., p. 255, No. 8, 1820. 

 Anomia — Wahlenberg. Nova Acta Upsal., vol. viii, p. 66, 1821. 



— — Turton. Traiisl. of Linne"s Syst. Nat., vol. iv, p. 282, 1802. 

 Terebratula — Fischer. Prog. Tereb., p. 50, fig. 1, 1809. 



Anomia — Dillwyn. Index to Martin Lister's MethodicaConchyl., &c., 



p. 447, 1823. 

 Ohthis — Balman. Vet. Akad. Handl., p. 110, pi. i, fig. 6, 1828. 



— — Hisinger. Letbaea Suecica, p. 70, pi. xx, fig. 6, 1837. 



— — Portloclt. Geol. Londonderry, &c., p. 453, 1843. 



— — Dav. Loud. Geol. Journ., vol. i, p. 61, pi. xiii, figs. 18 — 23, 



1847 ; and Bull. Soc. Geol. France, ser. 2, vol. v, p. 320, 

 pi. iii, fig. IG, 1848. 

 Strophomena — P/dllips and Salter. Mem. Geol. Surv., vol. ii, p. 381, 



1848. 



