282 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 4, 



"Wallachia, reaching apparently to the foot of the Carpathian moun- 

 tains, are composed of lacustrine deposits, purely of freshwater 

 origin ; although, from their containing a peculiar striated bivalve 

 like a Cardium, and from the mistaking of a large fossil Dreissena 

 for a Mytilus, by some early travellers, some portions of these de- 

 posits have been considered to be indicative of brackish water 

 conditions ; there having thus been an apparent admixture of marine 

 with the freshwater shells of these strata. 



Although I thought there was an error regarding the so-called 

 Mytilus, since I had seen the large-sized Dreissena, much resembling 

 a Mytilus, in the gravel or drift- deposits of Gallipoli and Bodosto, I 

 had for a long time no means of solving the doubtful point either 

 in its case or in that of its associate, the apparently marine Cardium ; 

 for, notwithstanding many dredgings made in different parts of the 

 Black Sea during the late war, I never could discover either of these 

 bivalves, or their representatives, living in its water, although a true 

 Mytilus is the most common living shell in the Black Sea. 



When carrying out my researches on the shores of the Danube, 

 however, I observed numerous valves of a shell resembling this 

 apparently marine Cardium, cast up together with marine and fresh- 

 water shells, near every embouchure of the river; and, notwith- 

 standing that my research was renewed on this account, no living 

 specimen could be obtained from the brackish waters of the adjacent 

 parts of the Black Sea. The conclusion to which I then came, in 

 consequence, was that the loose valves must either be fossils, and 

 had been carried out by the Danube from some of the deposits 

 bordering it, or that they were living either in some brackish lagoon 

 within the Delta, or in the river itself. 



The survey of the lakes of Kattabug and Yalpuk following soon 

 after, I then discovered that these shells were abundant within 

 them; the mollusc to which they belong living there as a really 

 freshwater bivalve in depths of 5 and 6 feet and more ; and I then 

 saw that the animal differed from the true marine Cardium in having 

 two elongated siphons. 



It was thus rendered more probable that the Cardium-like shell 

 in question is truly a freshwater bivalve, which had existed in, and 

 descended from, the great Oriental Lake period ; probably, however, 

 with some slight modification of character, since it seems to me to 

 be nearly identical with one of the so-called Cardiums found in the 

 Kertch deposits ; and with the one in the gravel at Gallipoli in the 

 Dardanelles, where it is associated with the Mytilus poly morphus of 

 some authors, the Dreissena of modern conchologists. 



It is important to make these preliminary remarks whilst contem- 

 plating the freshwater deposits of the southern parts of Moldavia 

 and Bessarabia, and of the Dobrutcha, in which apparently the same 

 bivalve is abundantly found, in order to remove the impression which 

 might exist, of its being a Cardium that has by a gradual transition 

 from a marine to a brackish, and finally to a freshwater medium, be- 

 come habituated to the latter as its natural element. From my own 

 observations I am inclined to view it as being originally a purely 



