ARALO-CASPIAN PROVINCE. 365 



water origin, being sometimes composed of myriads of Cyclades, or the shells 

 of Drvissena and Cardium, as in the islets near Astrakhan. It is believed 

 to indicate the former existence of a great inland sea, of which the Aral and 

 Caspian are remnants, but which was larger than the present Mediterranean 

 at an age previous to that of the Mammoth and Siberian Rhinoceros. The 

 present level of the Caspian is 83 feet below that of the Black Sea ; that of 

 the Aral has been stated to be 117 feet higher than the ('aspian, but is 

 probably not very different; their waters are only brackish, and in some 

 parts drinkable. The steppe limestone rises to a level of 200 — 300 feet above 

 the Caspian ; it spreads eastward to the mountains of the Hindoo Kush and 

 Chinese Tartary, southward over Daghestan and the low region E. of Tiflis, 

 and westward to the northern shores of the Black Sea. The extent to 

 w^hich it has been traced is represented by oblique lines on the map.* Some 

 of the Caspian shells still exist in the Sea of Azof and the estuaries of the 

 Dnieper and Dniester. Our information upon this seldom-visited region is 

 derived from the works of Pallas, Eichwald,t Krynicki,^ Middendorff, and 

 Sir Roderick Murchison. 



Aralo-Caspian Shells. 

 A, Aral; C, Caspian; B, Black Sea. 

 The Species marked * are found also in the steppe limestone. 

 *Cardium edule, L. C. (very small) B. Baltic. 



„ edule, var. (rusticum, Chemn.) A. C. B. Icy Sea. 

 *Didacna trigonoidfs, Pal. C (Azof. M. Hommaire), 



„ Eichwaldi, Kryn. (crassa, Eich.) C. B. (NikolaieflF). 

 Monodacna Caspia, Eich. C. 



,, pseudo-cardium, Desh. (pontica, Eich.) B. 

 Adacna laeviascula, Eich. C. 

 „ vitrea, Eich. C. A. 



* „ edentula, Pallas. C. 



„ plicata, Eich. C. B. (Dniester, Akerman, Odessa). 



„ colorata, Eich. C. B. (Azof, Dnieper). 

 *Mytilus edulis, L. C. B. (not in Middendorff s list.) 



„ latus, Chemn. B. 

 ♦Dreissena polymorpha. Pal. C. B. 



Paludinella stagnalis, L. (pusilla Eich.) C. B, (Odessa). Ochotsk. 



* ,, variabilis, Eich. C. 

 *Nei-itina liturata, Eich. C. on sea weed. 

 ♦Rissoa Caspia, Eich. C. 



„ oblouga, Desm. B. 

 ,, cylindracea, Kryn. B.§ 



■* From a sketch kindly prepared by Professor Ramsay. 



+ Geogr. des Kaspischen Meeres, des Kaukasus und des Siidlichen Russlands 

 Berlin, 1838. Fauna Caspio-Caucasica, 1841. 



X Bull, des Nat. Moscow, 1837. 



? The Veliitina (Limneria) Caspiensls, A. Ad. was founded on a specimen of 

 LimncBa Gebleri, Midd. (1851) from Bernaoul, Siberia. 



