ICHTHY0L1TES OF RIGA AND DORPAT. 
53 
sands, with ripple-mark surfaces, are in contact with red and green marls and 
marlstone. These remains are so gigantic (one bone measuring two feet nine 
inches in length), that they were formerly supposed to belong to Saurians ; but 
before our arrival at Dorpat, Professor Asmus, of that University, to whose 
labours the discovery and restoration of the best specimens are due, had completely 
convinced himself that they were parts of fishes. We shall again refer to these 
extraordinary ichthyolites, the largest of which, after a study of casts made by 
Professor Asmus, M. Agassiz has named Chelonichthys Asmusii 1 . 
Central Region of Devonian Rocks, or Geological Axis of Russia in Europe. Before 
our second journey and a visit to the central and southern provinces, we supposed 
with our precursors, that in proceeding from north to south, the observer would 
naturally pass over a regular succession from older to younger deposits, until the 
region of the granitic steppe was reached, where crystalline and carboniferous 
rocks occupy the surface. On our return from the Sea of Azof v 7 e undeceived 
ourselves, by discovering in the centre of Russia a broad zone of rocks, loaded 
with Devonian fossils 2 (see Map and the section beneath it). The structure of 
this dome-like mass is duly exposed in the gorges of the Oka above and below 
Orel, and in the denudations of the Don north and south ofVoroneje. Occu- 
pying the higher ground, about 800 feet above the sea, between the Oka, which 
flows northwards into the Volga and the Donetz, and other tributaries of the Don 
wdiicli run to the south, we already know 7 that this zone extends for nearly 200 
English miles in the parallel ofVoroneje and Orel ; and from the observations of 
Professor Blasius, we have strong reason to believe 3 , that, though much obscured 
1 Our Scottish friends of the Moray and Cromarty Friths will be rejoiced to learn, that their country 
has already produced fragments of this gigantic Chelonichthys Asmusii, which, until ho saw t 
perfect specimens from Russia, M. Agassiz had referred to Coccosteus. W e believe that the 1 
his Scottish specimens of the type to the researches of the lamented Lady Gordon Gumming. e trust 
that the next edition of the work of Mr. Hugh Miller, who is “ the genius of the Old Red Sandstone, 
may contain some description of a more perfect Chelonichthys in Scotland, even though it s rou e a 
rival in interest to his own Pterichthys. ... 
4 According to our custom, the expedition in travelling from the south was divided into two parties 
the one moving parallel to and at some distance from the other. Mr. Murchison and M. de \ erneui 
took the line of Kharkof, Kursk and Orel, and Count Keyserling that of the Don by Voroneje ; and, on 
meeting at Moscow, their results exactly agreed as to the existence of this mass of Devonian deposits 
which separates Russia into two distinct geological basins. 
3 Although he did not then class them as Devonian, our friend Professor Blasius, on his return to Ger- 
many in 1840, identified certain rocks at Orsha with others at Bolkhof, north of Orel, which we now 
know to be unquestionably Devonian. 
I 
