052 *** 
POSTSCRIPT. 
chambered shells with dentated lobes called Ceratites, one species of which, indeed, not having any of 
these indentations or serratures, might be referred to that division of Goniatites which are distinguished 
by rounded lobes. We thus learn how dangerous it is to generalize upon the age of a rock from the 
presence of any one fossil body ; for had these Ceratites been alone or even in predominance, some 
geologists might have associated the Siberian beds with the Muschelkalk, or even with older formations ; 
whereas a multitude of the most common of the Jurassic forms (including numerous Ammonites with 
their nacre) bespeak in the clearest manner the true age of these deposits. 
Lastly, we are indebted to our friend Colonel Helmersen, for having made known to us a highly im- 
portant and curious discovery of Professor Abich of Ddrpat, on the northern flank of the Great Ararat, 
near the monastery of Korverab and in the valley of the Araxes ; where he has detected numerous Pale- 
ozoic fossils, among which he cites the Spirifer speciosus, S. ostiolatus, S. aperturatus, with Orthidse, 
Tercbratulw, Lingulae, and the characteristic corals Catcnipora escharoides, Cyathophyllum fiexuosum, Fa- 
vosites, &c. 
This announcement is the more interesting to geologists, as no researches of other travellers have 
shown the existence of any formations of the palaeozoic age in those eastern regions which form the 
south-eastern extremity of our Map, PI. VI., the greater number of whose solid rocks have been referred 
to the cretaceous period. If, indeed, we might venture to throw out a surmise, we should be inclined 
to think, that the palaeozoic band on the upper Araxes is the eastern continuation of rocks of Silurian 
age which show themselves on the southern slopes of the Balkan, and constituting portions of the 
Thracian Bosphorus, may, after some detailed researches, be found here and there in the intermediate 
space of Pontus, Bithynia and Paphlagonia. 
