SECTION OF GREAT BOGDO. 
195 
state our conscientious belief, that Professor Eichwald is in error, when he sup- 
poses that the Ammonites Bogdoanus has a ventral siphon, an opinion which induced 
him to name the shell Clymenia Bogdoana. We have distinctly ascertained, that 
the siphon is placed exactly as in the Ammonites and Goniatites. 
But to resume our account of these singular outliers of the steppe. According 
to the Baron V. Humboldt, the summit of the greater Bogdo, of which the annexed 
woodcut is a section, is 53/ English feet above the ocean, and hence upwards of 
600 feet above the Caspian Sea. The beds dip south-west about 30°, and there- 
fore in an opposite direction to the chief masses of the Little Bogdo. 
The base of this hill consists of saliferous strata of argillaceous marl (a), from 
which brine-springs issue and deposit solid banks of salt in the adjacent lake ; beds 
of the thickness of a foot being sometimes formed in a single year. Gypseous 
courses occur, and marl so red that it is used as paint by the natives. To these suc- 
ceeds a considerable thickness of sandstone, the lower part of which ( b ) is soft, 
friable, and thin-bedded, and the upper (c) is a reddish grit, occasionally coarse- 
grained and hard, and containing rose-coloured quartz, Lydian stone and small 
striated concretions. Above these strata is a sandy, red and white argillaceous 
marl ( d ), which, from the alternation of courses of white marl, has a ribboned 
aspect, and this rock, in which Pallas found some salt, has a thickness of about 
200 feet. The summit is composed of a grey-coloured limestone ( e ) of about 100 
feet thickness, which divided into flags, has certainly very much the aspect of 
Muschelkalk. Near its base it is loaded with a great Gervillia ; and higher up 
with casts of a Perna, which in the general outline has some analogy with the 
Inoceramus rostratus of the Jura limestone (Goldf. pi. 115. fig. 3.). 
On the opposite side of the hill we found, in addition to the Ammonites Bogdo- 
anus, a compressed Mytilus somewhat resembling the M. eduliformis of the Mus- 
chelkalk, and small bivalves which may be referred to the genus Donax. The ge- 
neral character of these fossils, so very different from those we have observed in 
