ii8 Evolution and Distribution of Fishes 



the Welsh region, caused restricted deposits of typical ma- 

 rine fossils between the freshwater beds. 



The biological assemblage of the European Lower Old 

 Red rocks in part slightly resembles that of the Upper 

 Silurian, but on the whole is markedly different. Mitchell 

 (75-145) '^^^ Powrie (7^:413) early noted abundant 

 though poorly preserved plant remains. Parka decipiens, 

 spores of Pachytheca, the myriapod Kampecaris forfar- 

 ensis, species of Eurypterus and Pterygotus anglicus as well 

 as a very rich fish fauna were recorded. More recent 

 workers have greatly extended their lists, and particularly 

 have encountered abundant remains of such land plants 

 as the fern Archaeopteris, also Psilophyton^ Sigillaria, and 

 Calamites. 



Goodchild (77:591), Flett, and Campbell have given 

 detailed descriptions and lists from the north of Scotland, 

 while from the western part the Scottish Geological Survey 

 has contributed much. 



So abundant and typical in some of these Caledonian 

 beds are definite organisms that Goodchild (p. 600) clas- 

 sifies some of them thus : 



Myriapod Beds 



Volcanic Rocks 



Acanthodian Beds of Turin Hill 



Cephalaspis Beds of Auchtertyre 



Volcanic rocks 



Pterygotus beds of Carmylie, etc. 

 All of these, from our present knowledge, are freshwater 

 beds. 



The remarkable and unwieldy buckler-shaped Silurian 

 genera Cephalaspis (Fig. 9a) and Pteraspis are continued 

 into the lowermost or Caledonian rocks, that are exposed 

 in Forfarshire, in the Lome region, in Herefordshire, and 

 in East Wales (7<5:463), though the species as determined 

 by Traquair are different, Cephalaspis lyelli being the most 

 widely extended. The Acanthodians (Fig. 9e) or primitive 

 elasmobranchs of the Upper Silurian are represented by 

 Climatius ornatus and Parexus recurvus, while with these 

 in Forfarshire occur two types of Myriapod, Kampecaris 

 forfarensis and Archidesmus sp. 



