33 
RICH DEPOSIT OF DEVONIAN ICHTHYOLITES. 
however, where they contain concretions of calcareous spar, these sandy and marl- 
stone beds have afforded fishes’ scales disseminated in a cream-coloured marlstone ; 
and on following them up the stream to Marina and Poritz, the few feet of marl- 
stone visible at Ontoleva expand into cliffs twenty to thirty feet high, in which 
bands of purple and grey colours are found to be absolutely loaded with fragments 
of ichthyolites. Thanks to the repeated visits and liberal expenditure of M. Worth, 
who encouraged the peasants to break up this rock, a rich collection of these fossils, 
some of them in the highest state of preservation, has been obtained, a selection 
of which was transmitted toM. Agassiz 1 . 
In referring our readers to the descriptions of them by that great authority, 
whether in our second volume or in his own admirable work 2 , we may here briefly 
state, that with a number of species, identical with forms of the Old Red Sandstone 
of the north of Scotland, several new and remarkable genera are also found here. 
Of the former we may cite Biplopterus macrocephalus (Ag.) , Glyptolepis leptopterus 
(Ag.), Holopty chilis Flemingii (Ag.) , Actinolepis tuberculatus (Ag.) (a new genus and 
species common to Scotland and Russia), Dendrodus strigatus (Owen), D sigmoides 
(Owen), Lamnodus biporcatus (Ag.) (Dendrodus of Owen), L. Panderi or hastatus 
(Ag.) (Dendrodus of Owen), and Glyptosteus ( Bothriolepis , Eichw.) favosus (Ag.). 
Other forms as yet unknown in the British Isles (though belonging to typical De- 
vonian genera of that country) are species of the genera Onchus and Byssacanthus, 
Ag., which with the Psammosteus arenatus (Ag.) and some of the above-mentioned 
species range from Riga to Andoma, near Vitegra, in the deposits we shall describe 
in the next chapter as Devonian. Among the rarer forms are two species of Cte- 
nodus, a genus never found hitherto in any other system but the Carboniferous, 
and these have been named by M. Agassiz, Clenodus Keyserlingii and C. Worthii. 
Other species pertain to the new genera which that author terms Homacanthus, 
Haplacanthus, Narcodes, Naulas, Cladodus, tkc. 
These ichthyolites, like those mentioned in the next chapter, are not only of 
deep interest from proving the absolute identity of the Russian deposit with the Old 
1 The shells and other fossils of the Devonian system are mentioned in the next chapter, and the 
present introduction of this passage explanatory of the Devonian rocks of the Slavenka has solely been 
introduced because their discovery was made long after the third chapter was printed. Higher up the 
Slavenka and Ishora, the calcareous and marlstone beds mentioned in the text graduate into complete 
sands. Mr. Murchison, accompanied by Count Keyserling, M. Worth and M. Volborth, examined the 
chief localities of these Devonian beds at Ontoleva, Poritz and Marina, in August 1844. 
2 Monographic des Poissons du Systeme Devonien ou Old Red, liv. iii. 
