﻿I860.] 



MITCHELL OLD KED SANDSTONE. 



147 



On some of the fossils in the ahove list, a few brief remarks may 

 be allowed. Cephalaspis Lyellii, figured by Agassiz, is from Glammis, 

 Forfar ; it is by no means rare. Ptychacanthus dubius appears, from 

 specimens in the writer's possession and in the cabinet of Mr. Walter 

 M'Mcol at Tealing, to be the posterior portion (serrated along the 

 inner margin) of the head-plate of a species of Cephalaspis. 



The Aeanthodian fishes are new to science, and are about to be 

 described by Sir Philip Egerton in a 'Decade' of the Geological 

 Survey. Plectrodus has only recently been found here ; and any day 

 the stroke of the hammer may expose to our examination the com- 

 plete form of this curious creature. 



§ 3. The fossils connecting the Forfar and Kincardineshire beds 

 with the Upper beds of the Silurian System as developed in the 

 typical region of the latter, belong to the genera Cephalaspis, Plec- 

 trodus, and Onchus among the Fishes, and the genera Pterygotus and 

 Eurypterus among the Crustacea. There is also the curious organism 

 known as Parka. It may be questioned if our beds have one species 

 in common with the Ludlow rocks, although several genera seem to 

 range through both. 



§ 4. The fossils connecting the Forfar and Kincardineshire beds 

 with the higher beds of the Old Red Sandstone belong to the genera 

 Acanthodes, Diplacanthus, and, in a sense, Ctenacanthus. Acan- 

 thodes rises into the Middle Old Red Sandstone, and is also found in 

 the Carboniferous rocks. Diplacanthus, if it be that genus which 

 occurs in the Lower, advances no further than the Middle Old Red. 

 Ctenacanthus, though not recorded from either the Middle or Upper 

 Old Red Sandstone, finds its way into the carboniferous rocks. 



§ 5. The fossils occurring both in the Old Red Sandstone of 

 Herefordshire and in that of Forfar and Kincardineshire are 

 Cephalaspis Lyellii and Ptychacanthus dubius, with the genera On- 

 chus, Ctenacanthus, Pterygotus, Eurypterus, and Parka. 



§ 6. With regard to the fossils peculiar to the Forfar and Kin- 

 cardineshire beds or to their equivalents in England, and deter- 

 mining them to belong to a distinct and well-marked zone of the 

 Old Red Sandstone, it may be said that the entire Fauna and Flora 

 are peculiar. There may be one or two doubtful cases, so far as 

 specific identity is concerned; but the facies is undoubtedly cha- 

 racteristic of the horizon of these beds. The genus Parka is highly 

 characteristic. 



§ 7. Distribution of the Fossil Remains over the Counties of Forfar 

 and Kincardine. — Over this extensive area there is almost complete 

 identity in the fossil organisms. Of this some illustrations may be 

 given. Cephalaspis Lyellii has been found over the entire district 

 from Balruddery on the S.S.W., and on the confines of Perthshire, to 

 Canterland, close upon the German Ocean, in Kincardineshire — as at 

 these particular localities : — Balruddery, Tealing, Glammis, Carmylie, 

 Leysmill, Carsegownie, Brechin, and Canterland. The Aeanthodian 

 Fishes are now known to occur in five localities: — Balruddery, Tealing, 

 Forfar, Farnell, and Canterland. These fishes were first detected by 

 the author in beds at Farnell in July 1857; but they are now turning 



