312 H. M. AMI — KNOYDAKT FORMATION OF NOVA SCOTIA 



is completely known. One piece of dorsal shield in counterpart shows the im- 

 pression of the supposed branchial pouches on one side. 



" The pointed fragments in the collection may be Cephalaspidian cornua, but are 

 uncertain. There is also present the typical Onchus MurcJdsoni. 



" Most interesting is one small fragment of Psammosieus, with ornament identi- 

 cal with that of P. anglicus.* In this fossil the chambers of tlie middle layer are 

 larger than in our unique plate. 



" On the whole, I should place the McArras Brook beds on the same horizon as 

 the Lower Old Red Sandstones-Cornstones of the Hereford district of England 

 above the passage beds." 



Conclusions 



It may thus be safely concluded, with the evidence at hand, together 

 with the learned opinion of Messrs Arthur Smith-Woodward and R. H. 

 Traquair, that we have in Nova Scotia an area of Lower Devonian rocks 

 which represent well in America the lower portion of the Old Red Sand- 

 stone of Europe. This latter series of strata, together with the Devonian 

 rocks proper. Sir Roderick jNIurchison held to be the result of "difierent 

 geographical conditions of the same period." The same statement may 

 be uttered with all truth in North America. From the character of the 

 strata, it is evident that lacustrine deposits were laid and shallow-water 

 conditions prevailed throughout the Knoydart area in Ko-Devonian 

 times, and a lake similar to lake Orcadie,lake Caledonia, lake of Lome, 

 the Welsh lake, etcetera, of Great Britain, so graphically described by 

 Sir Archibald Geikie, existed in Canada, to which the name l<ilce Pidou 

 might appropriately be given. 



It ma}' here be remarked that the Knoydart formation of Nova Scotia 

 finds a near equivalent in the Eo-Devonian strata of the Campbellton for- 

 mation in the Baie des Chaleurs region. To the lake in which Coccosteus 

 {Phlyctxiiaspis), Cephalasjns, Protodus, Ctenacanthus, Acanthodes, Cyclora, 

 etcetera, once flourished in the Bay des Chaleurs region, the name " lake 

 Chaleur " is suggested. 



It is an interesting fact to note that much contemporaneous volcanic 

 ash materials constitute the deposits of both these ancient Paleozoic 

 lake basins — "lake Pictou " and "lake Chaleur." 



*See Traquair, Ann. Mag. Nat. Hist., ser. 7, vol. ii, 1898, p. 67, pi. 1, figs. 1, 2. 



