ii6 Evolution and Distribution of Fishes 



basins in which the late parts of the system were deposited, 

 only partially correspond with those of the older lakes." 



In a later study by Goodchild (77:591) he says: "as 

 regards its mode of origin there appears to be evidence of 

 a satisfactory nature that the whole of this vast formation 

 was accumulated under continental conditions, partly in 

 large inland lakes, partly as torrential deposits of various 

 kinds, partly as old desert sands, and partly as the results 

 of extensive volcanic action." He estimates the thickness 

 of the lower series as reaching in places to 20,000 feet, 

 while the upper, that he divides into an Orcadian, a Nairn, 

 and an Elgin set, may reach 17,000 feet. 



As might be expected, the rocks that compose the Lower 

 Old Red Sandstone, while largely of a reddish ferruginous 

 tint, include red shales, grey and yellow sandstones, occas- 

 ionally — usually thin — limestone, or "cornstone" beds, and 

 in Forfarshire hard close-grained grey flagstones. Pow- 

 rie has described these in detail (72:413), and specially 

 refers to "one very extensive and highly fossiliferous Fish- 

 bed, holding an intermediate position among the flaggy 

 beds, continuous and apparently equally extensive with 

 them." He "found this fish-bed in Carterland Den in 

 Kincardineshire, near Farnell, at Turin Hill, in some quar- 

 ries south of Forfar, in many places on the Sidlaws, in Bal- 

 ruddery Den in Forfarshire, and in Rossie Den in Perth- 

 shire. It thus extends over a range of more than twenty 

 miles " As to its contents he says: "wherever this deposit 

 has been discovered it abounds in ichthyic and crustacean 

 remains, the former being far the more abundant." 



Hull (7J: 225) has fairly well synopsized the condition 

 of affairs in the relation of the marine Devonian to the 

 freshwater Old Red Sandstone thus (p. 274) : "At the 

 close of the Upper Silurian period, represented in Ireland 

 by the Glengariff beds, in Wales by the Upper Ludlow 

 and Passage beds, and in Scotland by the Lower Old Red 

 Sandstone, there was a general elevation of all the northern 

 and western portions of the British Isles, accompanied by 

 flexuring of the strata, and followed by extensive denu- 

 dation. In the area of the south of England, however, 

 and adjoining continental districts it was otherwise. Here 



