38 DEVONIAN ERA. 



pound eyes ;" much resembling the minute forms Mysis and 

 Cuma, which are arranged very low down among the decapods ; 

 even more resembling the larva of the common crab. And he 

 makes the remark, highly worthy of notice here, that "the 

 coincidence in essential structure between such minute and 

 embryonic forms and these gigantic denizens of the old seas 

 becomes most remarkable and interesting, as bearing on the 

 course of development of life throughout geological epochs." 1 ] 

 Throughout the dense masses of the Lower Silurian forma- 

 tion, and the lower of the similar masses of the upper each 

 representing a long space of time there are no indubitable 

 remains of fish to be found. In the Upper Ludlow rocks, at 

 length, a few fragments appear, consisting mainly of spines or 

 defences, and indicating some small individuals of the placoid 

 family. This is a remarkable event, as it is, so far as we as 

 yet know, the first appearance of vertebrated animals on the 

 surface of the globe. 2 



DEVONIAN ERA. FISHES ABUNDANT. 



WE now advance to a new chapter in this marvellous history 

 that of the Devonian era. The term Devonian System is 

 applied to an important and conspicuous group of strata, 

 overlying the Silurian, and largely developed in the South 

 of Devonshire (whence the name), and in Cornwall, South 

 Wales, Herefordshire, Shropshire, and Worcestershire ; also in 

 Scotland, the valley of the Khine, Kussia, and the western 

 states of America ; besides, in all probability, many parts of 

 the world as yet unexplored. In Scotland, the Great Gram- 

 pian elevation, composed of granite and gneissic rock, is skirted 

 by a dense formation of conglomerate and red sandstone, ex- 

 tending in a sweep from Dumbarton to Stonehaven, and so on 

 to Morayshire, Ross, and Caithness. This passes by the 

 general name of the Old Red Sandstone, which was at first 

 used as an appellative for the system ; but it has latterly been 

 abandoned, as redness is not found to be a prevailing pecu- 

 liarity of the strata in other countries. In Russia, a surface as 

 large as the whole of Great Britain is occupied by this forma- 

 tion. It reaches a thickness of ten thousand feet in England. 



The general forms of life prevalent in the Silurian era are 

 continued in the Devonian, with the addition of a large de- 



1 Keport, Brit. Assoc., Cheltenham, 1856, p. 76. 

 2 See Proofs and Illustrations, No. 5. 



