DEVONIAN AND OLD BED SANDSTONE. 413 



Forfar, is remarkable for the abundance of beautifully preserved 

 Acanthodian Elasmobranchs. It is also imperfectly known in 

 Galicia and in Spitzbergen ; while it occurs in an admirable 

 state of preservation in the Lower Devonian shales of Camp- 

 bellton, New Brunswick, where Phlyctcenaspis is commoner 

 than in Europe and Pteraspis seems to be wanting. 



The next Devonian fish-fauna is best known in the north 

 of Scotland, where it is found in the Old Red Sandstone series 

 deposited in " Lake Oread ie." It is specially characterized by 

 the abundance of the anomalous armoured Arthrodira (Cocco- 

 steus, Homosteus) and of Crossopterygian fishes belonging to 

 the sub-order Rhipidistia (Glyptolepis, Osteolepis, Thursius, 

 Diplopterus) ; while the Dipnoi make their first appearance 

 (Dipterus), and one genus (Cheirolepis) represents the dawn 

 of the Actinopterygian fishes. Except an extremely rare 

 Cephalaspis (of which only one specimen has hitherto been 

 discovered in northern Scotland), the two lower orders of 

 Ostracoderms are now wanting; but the highly specialized 

 order of Antiarchi appears, abundantly represented by the 

 genus Pterichthys. A few small specialized Acanthodians also 

 remain (Mesacanthus, C heir acanthus, Diplacanthus). A corre- 

 sponding fauna is indicated in North America in the Corni- 

 ferous Limestone extending across New York and in several 

 other of the United States, where undoubted Chimaeroid teeth 

 are met with for the first time. 



The Upper Devonian fish-fauna is characterized especially 

 by the Ostracoderm Bothriolepis, by armour-plated sharks like 

 Psammosteus, and by the Crossopterygian genus Holoptychius ; 

 but there are several local variations, and all three genera do 

 not always occur together. Dipnoan fishes are still abundant 

 (Phaneropleuron, Scaumenaria), but the Arthrodira are rarely 

 met with. This fauna occurs in the red and yellow sandstones 

 of the Old Red Sandstone series both to the north and to the 

 south of the Grampians ; in the west of England ; in Belgium, 

 Germany, north-western Russia, and Spitzbergen; in the 

 province of Quebec, Canada, and in the Chemung (Catskill) 

 Formation of the United States. Fragments are also recorded 

 from Queensland. 



