PASSAGE FROM OCEANIC TO BRACKISH WATER CONDITIONS EXPLAINED. 301 
To return, however, to the true Aralo-Caspian strata, we consider the chief masses 
of white limestone occupying the low hills to the south of the coal region of the 
Donetz, and ranging by Mariopol to Odessa and thence into the lower country ot 
Bessarabia on the western shores of the Black Sea, to be of this age. We place 
upon the same parallel the upper shelly strata described in the Crimsea, including 
the chief limestones around Kertch, and the deposits of the cliffs of Kamiusch 
Burun and Taman, and also the limestones on the northern and western shores 
of the Black Sea. 
We would here refer our readers who seek for the details of the formation in 
that region, to a memoir by one of us upon the Crimsea, in which we have described 
these deposits, as being there composed of courses of argillaceous marls, clays, 
calcareous marls, concretions, ferruginous bands, agglutinated shells (faluns), 
and soft, spongy, shelly limestone'. The soft limestone, usually white, is the 
best type of the whole formation, and largely used as a building-stone both at 
Odessa and in the Crimsea, it has afforded a great number of organic remains. In 
some bands associated with it we found an infinite quantity of small Paludinse ; 
but at Taman, as at Novo Tcherkask, the most abundant forms are the small and 
peculiar Cardiacete, and the Mytilus polymorphus (Dreissena of Van Beneden). Of 
the former M. Deshayes described twenty species, and whilst these are asso- 
ciated with Mytili and a Modiola which must have lived in brackish waters, we 
remarked the almost total absence of Gasteropods of marine origin ; the Paludime, 
Melanopsidse and Limnese which were then enumerated, being unquestionably of 
freshwater origin, and one of them undistinguishable from species now inhabiting 
the embouchure of the Dniester ( Neritina Danubialis ) . 
In addition to these decisive concliological facts, an independent proo as 
recently been obtained of the manner in which beds of a purely marine c aracter 
passed into these brackish steppe limestones. Pallas and Rathke had both alluded 
to the bones of certain Cetacea found in the peninsula of Taman ; and Pro essor 
Eichwald had referred the head of one of these animals to a Dolphin, and named 
it Ziphius prisons. Obtaining possession of this specimen for the Museum of St. 
Petersburg!!, Professor Brandt worked the head of the colossal creature out o the 
rock in which it was imbedded, and pronouncing it to belong to a new family of 
whales, has described it under the name of Cetotherium RathUi. This fossil genus 
appears to form a new link in the animal kingdom, and is more nearly allied to the 
. M . E. de Verneuil, M4m. de la Soc. G&l. de Fr. vol.iii. with 6 plates. 
