Fossil Fishes. 47 



they support the coal formation in the southern parts of Wales. The 

 middle division of the old red-sandstone consists of red and green 

 marls, with numerous beds of concretionary limestones called corn.'- 

 stone, and some beds of very hard sandstone ; it is this part of the 

 formation which contains the debris of the Cephalaspis. There has 

 not been the slightest trace of any other kind of organic body dis- 

 covered in this division of the formation, these fragments of fishes ex- 

 cepted, which, at the same time, characterise it in a very peculiar 

 manner. They have been found by Mr. Murchison himself in the 

 different parts of this division, in the counties of Salop, Hereford, 

 Worcester, Monmouth, and Brecknock, over an extent of nearly 

 3000 square miles, and always occupying tlie same geological hori- 

 zon. This group of cornstones has likewise a very considerable thick- 

 ness, equal probably to that of the division immediately above it. 

 At the same time, Mr. Murchison thinks that the remains of the fish- 

 es are especially abundant at the lower portion of this middle divis- 

 ion. In the lowest division of the old red-sandstone, below the hor- 

 izon of the Cephalaspis, Mr. Murchison found, at Downton-Hall, 

 near Ludlow, not more than the fragment of a head, with a portion 

 of the scaly cuirass, evidently belonging to the Diptcrus Macrole- 

 pidotus ; and at Tinmill, near Downton-Castle, some small Ichthy- 

 odorulites, accompained by a new species of Pileopsis, and a new 

 species o{ Avicula. In this last locality, the transition from the old 

 red-sandstone to the Ludlow-rock sandstone which it covers, was 

 very distinctly perceived. The situations in which the fossils of this 

 formation occur most frequently, are Whitbach near Ludlow, the 

 Whyle, the Bromyard Road, Sutton-Hill, Downton-Hall, Menai- 

 bridge, and Abergavenny. Mr. Murchison imagines that the con- 

 cretionary nature of the limestones of the old red-sandstone forma- 

 tion, and their being broken into small pieces so as somewhat to re- 

 semble a conglomerate rock, has prevented the discovery hitherto of 

 native fishes, but he does not despair of discovering them in the 

 more compact sandstones. Neither has he found any in the vast 

 masses of concretions which have somewhat of a subcrystalline struc- 

 ture, and an occasional thickness of about twenty feet. In Scotland, 

 however, and, amongst other places, at Glammis in Forfarshire, some 

 specimens of Cephalaspis, in fine preservation, and almost entire, 

 have been discovered, and have been transmitted to me by Profess- 

 or Jameson and Mr. Lyell. Lastly, the scales of the old red-sand- 

 stone of Fifeshire, which have been described by Dr. Fleming, be- 



