Fossil Fishes. 51 



"By descending still lower, we arrive at the system of slaty rocks 

 of the southern part of Wales, which Professor Sedgwick has exam- 

 ined with such minute care, and in which he has never discovered 

 the least trace of fishes. Thus we have under the old red sandstone 

 a geological scale of many thousand feet extent, the several degrees 

 of which have been most assiduously examined by geologists of the 

 first-rate eminence, and upon which the commencement of the his- 

 tory of fishes may be with certainty inscribed at the height of the 

 Ludlow rocks' formation, and possibly even at that of the Dudley 

 rock formation. But, however this may be, we may safely state 

 that it is in the Greywacke group that fishes begin to appear. 



" These facts are not of a kind in any degree to countenance the 

 ideas which are at present most generally received concerning the 

 succession of organized beings, and the consecutive appearance of 

 animals of the radiata, then the mollusca, the articulata, and the 

 vertebrata, since we find them here commingled together. Their 

 progressive development, on the contrary, presents phases peculiar 

 to each of these classes, and is expressed by various metamorphoses, 

 to which each of them is subjected in their specific characters, and 

 in their mutual arrangements." 



Of the genus Eurynotus, the following British species are descri- 

 bed: — 1. E. crenatus, found by Professor Jameson in the limestone 

 slate of the Burntisland district, and also in the limestone of Bur- 

 diehouse, by Dr. Hibbert. 2. E. Jimbriatus, in the clay-ironstone 

 of Wardie, where it was noticed by Lord Greenock. Of the genus 

 Platysomus, the following British species are described: — LP. 

 striatiis, in the English magnesian limestone. 2. P. maCrurus, Eng- 

 lish magnesian limestone. 3. P. parvus, magnesian limestone of 

 Low-Pallion, Northumberland. Of the genus Gyrolepis, the fol- 

 lowing British species are described: — I. G. Albertii, at Wickwar, 

 near Bristol. 2. G. tenuistriatus, in osseous breccia at Wickwar. 

 3. G. maximus, at Wickwar? 4. G. giganteus. The immense 

 scales, found by Professor Jameson and others in the old red sand- 

 stone of Fifeshire and Angus-shire, belong to this species. Of the 

 genus Dipedius, the following are British species :— L D. politus, a 

 species characteristic of the lias of Lyme-Regis : Then follow geo- 



These four formations of Murchison, interposed between the English old red sand- 

 stone and the transition rocks of the Wernerian school, as described by Jameson 

 are considered as forming a grand group, and named Silurian from the Silures 

 the ancient inhabitants of the district where these rocks occur.— Edit. 



