530 Murchison' s Silurian System. 



been subjected to fire. Mr. Murchison traced these glazed 

 or varnished fragments to a great escarpment, which having 

 been subjected to a downcast, is for the space of a mile 

 submerged in a turf bog, the ends of the strata alone ap- 

 pearing in the banks of the stream. This glazed appear- 

 ance Mr. Murchison ascribes to long continued immersion in 

 the bog water, which is impregnated slightly with a vegetable 

 acid. The course and flexures of the carboniferous lime- 

 stone is delineated on the map, which forms an important 

 part of Mr. Murchison's work, together with its various eleva- 

 tions and subsidencies. At the Ferns of Csermarthenshire, 

 where the rock is a thousand feet in thickness, it is thrown 

 up so as to form the highest point of land in South Wales ; 

 and in other situations it dwindles in thickness to the size 

 of a mere bed, and disappears at the mouth of the Towy 

 river, and is no further traceable on the Sea cliffs.* 



* The following is a list of the organic remains fonnd in the carboni- 

 ferous limestone by Mr. Murchison. 



Chief Localities. 



,, T-, . i • u • i\/t n * oqq S Coal Brook Dale, and 



" Productus hemisphaencus, M. C. t. 23». < Oswestry 



Martini, M. C. t. 318 f. 2. 3 & 4. Clee Hills.'&c. 



comoi'des, M. C. t. 239. Salop and South Wales. 



costatus Phill, pi. 7. f. 2. Oswestry, &c. 



margaritaceus Phill, pi. 8. f. 8. "| 



sotossus, pi. 8. f. 9. 



punctatus, Phill Phill, #1. 8. f. 10. I 



Spirifer attenuates Phill, pi. 9. f. 13. f Pembrokeshire. 



connivens Phill, pi. 11. f. 2. 



imbricatus Phill, pi. 10. f. 20. 



filiarus Phill, pi. 11. f. 3. J 



papilionaeeus Phill, pi. 11. f. 6. ~) 



radialis Phill, pi. 11. f. 5. > Pembrokeshire. 



resupinatus Phill pi. 11. f. 1. > 



semicircularis Phill, pi. 9. f. 15 & 16. Littleton on Severn. 



, bisulcatus, M C. t. 494. f. 1 & 2. 1 



cuspidatus, M. C. . t .120. f c) • mu Shropshire. 



distans, M. C. t. 494. f . 3 C > r 



octoplicatus, M. C. t. 562. f. 2. 3 & 4. J 



Terebratula fungites, M. SS. Phill. ~i 



ambigua, Phill, pi. 11. f. 21. . V Pembrokeshire. 



radiculis Phill, pi. 12. f. 40 & 41. > 



Crinoidea occur in vast profusion, including genera and species 

 described by Miller from the limestone of Bristol. Corals also are in 

 parts very abundant, Orthocerata are very rare, and I never found one 

 with well-marked characters. TrUobites are also scarce, but a few 



