Murchison's Silurian System. 531 



The dislocations of the carboniferous limestone along the 

 margin of the South Wales coal-basin are next pointed out, 

 and illustrated by many natural sections, afforded by the 

 rich mountain scenery of South Wales. " The western end 

 of that portion of the escarpment of the South Wales coal- 

 field, which is occupied by the Caermarthen Ferns, exhibits 

 a very powerful transverse fault, by which the upper strata 

 of the old red sandstone have been so thrown up, as to 

 occupy the summit of Fan-sirgaer, 2200 feet above the sea ; 

 while in the contiguous mountain of Carreg-o-gof, the same 

 beds, covered by carboniferous limestone and millstone 

 grit, lie at the height of not more than 1500 feet; and hence 



examples of them have been detected by the Earl of Cawdor in the 

 coast cliffs near Stackpole, Pembrokeshire, among which are caudal 

 portions of Asuphus seminiferus and A. granuliferus of Phillips. The 

 Icthyodorulites of this formation are of peculiar forms, and have been 

 described by M. Agassiz ;> among them is the Cotenacanthus tenuistriatus 

 of the Clee Hill limestone ; other species occur near Bristol. 



Considering this formation to be well know a, I did not collect many 

 organic remains, so that after all the list is very incomplete. We may 

 however consider it as a sample of specimens taken from various locali- 

 ties ; and viewing them in this light, it is worthy of remark, that every 

 species above enumerated has been previously described by Professor 

 Phillips as occurring in the limestone of this age in other and distant 

 tracts. On the southern edge of the South Welsh coal-field, particu- 

 larly between the Mumbles and Pennard, west of Swansea, the car- 

 boniferous limestone has been diligently explored by my friend Mr. 

 Dilhwyn, M. P., whose skill in conchology has enabled him to detect 

 many species in addition to those commonly observed in the formation. 

 In his list, which has not yet been published, he enumerates — 



Ammonites ? and Goniatites 2 ; Bellerophon, several species ; Cirrus ? 

 Beveral ; Dentaleum 1 ; Euomphalus several ; Eulima ? 1 ; Littorina, 3 ; 

 Lutraria 1; Melania, 3; Natica, 1 ; Orthocera, several; Turbo, 1 ; Trochus, 

 3 ; Turritella, 4 ; Rotella 1 ; &c. ; among these also Professor Phillips has 

 also recognised many published in his work, while Mr. J. de C. Sowerby 

 coincides with me in opinion that not one of these species has yet been 

 found in the old red or silurian systems," 



3 z 



