588 



ORGANIC REMAINS OF THE OLD RED SYSTEM. 



masses of limestone which have been described ; but they are generally in fragments, 

 there not having yet been any example of an entire fish found in England. This con- 

 dition of the fishes is in some degree accounted for by their structure, as subsequently 

 explained by M. Agassiz ; though it might be supposed that their mutilated state would 

 also seem to prove, that they had not been suddenly killed and entombed, but were long 

 exposed to destructive sub-marine agencies, such as the attacks of animals, currents, 

 concretionary action, &c, by which they were dismembered 1 . 



The fragments being usually of blueish and purple plum-colours, are strongly 

 contrasted with the dull red tint of the surrounding rock, and thus the geologist has 

 little difficulty in recognising even the smallest portion of these ichthyolites. Their 

 peculiar colour is probably due to the presence of phosphate of iron, which has com- 

 municated a similar tint to the fishes of the Caithness schist. (See Trans. Geol. Soc. 3 

 vol. iii. p. 142.) 



Notwithstanding the most assiduous search by myself, assisted by Dr. Lloyd of Ludlow 

 and the Rev. T. T. Lewis of Aymestry, no shells have yet been found associated with 

 these fishes in the central or cornstone formation, wherein they most abound. In one 

 situation, however, at the Daren near Crickhowel, I found the impression of a large 

 scale of an undescribed species of Holoptychus ?, in beds of younger age than the great 

 mass of cornstones, and as I have also discovered the remains of other species in the 

 lowest or tilestone division, the Old Red System may now be fairly said to be cha- 

 racterized throughout by ichthyolites peculiar to it. 



That fishes existed in strata of the age of the Old Red Sandstone was first pointed 

 out in the year 1827 by Professor Sedgwick and myself. In a geological memoir upon 

 the Caithness schists, certain fossil fishes were described which we had obtained from 

 strata, proved by actual sections to form part of the Old Red System of the Highlands, 

 and it was therefore gratifying to find that one of the species which I detected in the 

 very bottom of this system, near Ludlow, was recognised by M. Agassiz to be identical 

 with the Dipterus macrolepidotus of the north of Scotland. That celebrated ichthyolo- 

 gist has, indeed, the real merit of having cleared away all the zoological obscurities which 

 previously hung over this branch of our subject. Upon his arrival in this country (to 

 which he was attracted by the well-merited honours conferred on him 2 ) geologists at 

 once placed all the fruits of their labours in his hands. The specimens of fishes col- 



1 The beautiful entire fish, Cephalaspis Lyellii, PI. 1. f. 1., (of which species I have found hundreds of frag- 

 ments in England and Wales) was discovered in the Old Red Sandstone of Forfarshire ; and Professor Agassiz 

 has with great propriety named it after the geologist who, in addition to his excellent works upon the general 

 principles of our science, was among the first to explain the structure of his native county, Forfar. The ich- 

 thyolites of Forfarshire were, however, first described by the Rev. Dr. Fleming. See Edinb. New Phil. 

 Journal, No. 45. p. 137. 



2 " The Wollaston Medal," presented to him by the Geological Society, 1834. The British Association for 

 the Advancement of Science has since done honour to itself, by granting money to M. Agassiz to aid the pub- 

 lication of his great work. 



