340 M. Agassiz on Fishes. 



are described: 1. Ch. TraiUii, found by Dr Traill in the slates 

 of Pomona ; 2. Ch. Uragus, found at Gamrie, where there is 

 an interesting deposit of fossil fishes in a red sandstone, which, 

 in the regular succession, is below the coal formation. Of the 

 remarkable genus Cephalaspis, the following British species 

 are mentioned, 1. C. Lyellii, of which fine specimens were 

 found in the old red sandstone of Forfarshire many years ago 

 by Professor Jameson, and since by Mr Lyell and others ; 2. 

 C. Lewisii, found at Whitebach ; 3. C. Lloyd'n, common in the 

 old red sandstone in Wales. The consideration of this genus 

 leads our author to the following observations on the strata in 

 which the most ancient Jish are found. 



The truly astonishing character of the genus (Cephalaspis) afford 

 me a renewed opportunity of remarking how much the several por- 

 tions of the frame of the animals of the most ancient epochs, exliibit 

 a uniformity of structure, and at the same time, types of the animal 

 kingdom which are but little distinguishable among themselves. 

 Here, for example, the bones of the head are all as one, the scales 

 are united in very elevated bands, and the rays of the fins remain 

 covered by the membrane which elsewhere surrounds them ; whilst 

 the whole animal, to a most extraordinary extent, resembles the 

 Trilobites, which have somewhat preceded the Cephalaspis in the 

 series of their creation. This example alone would suffice to mani- 

 fest the constant laws which regulate the succession of living beings, 

 and their progressive development, if the whole class of fishes Mere 

 not itself a continual demonstration of it. 



All the species of the genus Cephalaspis have been found in the 

 old red sandstone of England and Scotland. It is not, therefore, as 

 has been asserted, in the mountain-limestone, and consequently still 

 less in the Zechstein or Magnesian limestone, that the vestiges of the 

 most ancient fishes have been found. Their presence mounts U]) to 

 an epoch yet more distant; for it is now certain that they are found in 

 very considerable number in the old red-sandstone. And, moreover, 

 even this formation is not the oldest in which fossil fishes have been 

 discovered. But since the Cephalaspis itself belongs to an epoch so 

 very remote, and since it is of the highest importance for the science 

 of Paleontology to determine exactly the formation in which the first 

 traces of fish are found, I deem it proper now to enter into some de- 

 tails concerning all the species of fossil fishes, the debris of which 

 have been discovered in the most ancient beds of the crust of the 

 globe, even although their organization will compel me, in part at 

 least, to postpone their description to the 3d volume of this work. 



In order that I may be able the better to fix and point out my in- 

 dications concerning the strata in which the most ancient fish occur, 

 and also that no uncertainty may remain concerning the geologi- 

 cal age of their beds, it will be useful here to transcribe in a sum- 

 mary way the results of Mr Murchison's researches into the fossilifer- 

 ous stratified rocks below the coal formation — and these indications 



