356 The American Geologist, June, 1898 
D. eifelensis in Belgium (Eifel limestone) are facts which 
very strongly favor such a reference. 
If we succeed in proving a connection between the waters 
of northwestern America and those of Europe in the earlier 
part of the Devonian era and a further connection with the 
Appalachian area in middle and later Devonian time, we must 
forthwith look in Europe or Asia for the ancestors of the Ohio 
placoderms. And the evidence there attainable is very sig- 
nificant. Great fishes of similar character have been found 
and described from Russia and Bohemia in rocks of equal age 
with those of Ohio and in some instances of greater antiquity. 
No species is identical, but the general character of the fauna 
is such as to leave no doubt of its taxonomic relations. The 
great Middle Devonian limestones of the Eifel (Belgium) and 
the Baltic governments of Russia, all more or less contempo- 
raneous with part of the Scottish Old Red sandstone, contain 
a wealth of fish fossils which the labors of Pander, Schmidt 
and others have made known to the paleontologist. Here oc- 
cur Asterelepis, Bothriplepis, Holoptychius. Dendrodus, Pter- 
ichthys, with Coccosteits, Homos/ens and Heterosteus and oth- 
ers more or less closely related to the Ohio forms, and in this 
region apparently must we seek the ancestors of the latter. 
But here we encounter another break. The Lower Devonian 
rocks do not occur in Russia, but the "middle Old Red sand- 
stone reposes transgressively on various members of the Silu- 
rian rocks."* 
To Scotland and England we must turn for the missing 
chapter in the history, wdiere in the Caithness and Forfarshire 
flags and Herefordshire cornstones and tilestones of the lowest 
Devonian a fauna occurs deeper in position and older in time 
than any of those already mentioned. But from this fauna 
all the great placoderms are absent and their place is occupied 
by smaller fishes of strange structure and uncouth appearance. 
Pteraspis, Cephalaspis, Attcheiuisjiis, etc., characterize this 
zone, few of them exceeding a length of twelve inches. They 
present in general the placodermic structure in that their fore 
parts were encased in bony armor, while their hind parts 
possessed no such protection. It is true that none of the pre- 
viously mentioned species are found accompanying these 
*Murchison. "Siluria," 1859, p. 381. 
