52 
DEVONIAN ROCKS — RIGA TO DORPAT. 
yet been discovered, their rise from still lower strata at Starai Russa, to which we 
have already adverted (p. 45), may induce researches and sinkings, which, if 
successful, would be of great benefit to the Baltic provinces. 
Throughout a wide space east of Riga and the Diina, the Devonian rocks appear 
chiefly, in the form of incoherent and lightish coloured sandstones, the disintegra- 
tion of which may have contributed to form the dunes of blown sand which are 
here so prevalent. Between Riga and Dorpat, red sandstone, both yellowish white 
and dark red, crops out at intervals, associated, however, with stiff, reddish clays. 
On the whole, the northern zone of the Devonian age maintains throughout 
Courland and Livonia the same lithological characters as in the governments of 
Novogorod and St. Petersburgh, and containing much more calcareous matter than 
the same rocks in Olonetz and Archangel, is charged with the remains both of 
mollusca and of fishes. This association has been noticed on the Volkof, at 
Tchudova, Korostino and in Courland, and we would now merely observe, that at 
several localities east of Riga, where calcareous matter is interlaced with sand and 
clay (Roop, &c.), the Terebratula Livonica (V. Buch) and other typical shells are 
associated with remains of ichthyolites. 
Our acquaintance with the fossil fishes which occur in the vicinity of Riga, we 
owe to M. Pander, whose fine collection, made chiefly on the banks of the little 
river Aa 1 , was submitted to our inspection, and from which we were liberally fur- 
nished with a number of characteristic specimens. Of these we will now merely 
say, that several forms appeared to us, when on the spot, to be identical with species 
which occur in the Old Red Sandstone of Scotland, whilst others w T ere unknowm 
to us. The subsequent examinations of Professor Agassiz and Professor Owen, 
some of the results of which will be given at the end of this chapter, completely 
confirm our view, for among these Riga fishes, three species of Dendrodus* (Owen) 
are identified with knowm Scottish forms*. 
The low cliffs at Dorpat afford, however, the most remarkable specimens, we 
venture to think, of all fossil fishes ever yet discovered. They occur in about 
the middle beds of a section, where micaceous, red and green, finely laminated 
1 The rivers Salis, Raune, Ammat and Aa are mentioned by Strangways as flowing in rocky valleys of 
Lithuania, the last-mentioned of which, nearTreyden, is remarkable for its caverns. Geol. Trans, vol. i. 
p.12. 
2 In the sequel it will be seen, that Professor Agassiz divides the Dendrodus (Owen) into three genera, 
Dendrodus, Lamnodus and Cricodus. The specific forms, however, are the same in Russia and in Elgin- 
shire, Scotland. 
