162 MARINE PROVINCES. 



V, Aralo-Gaspian Province. 



The only inland salt-seas that contain peculiar shell-flsh are 

 the Aral and Caspian. The shells chiefly consist of a remarkable 

 group of Cockles (Cardium), which burrow in the mud. No 

 explorations have been made Avith the dredge, but other species,, 

 probably still existing in these seas, have been found in the beds 

 of horizontal limestone which form their banks and extend in 

 all directions far over the steppes. This limestone is of brackish- 

 water origin, being sometimes composed of myriads of Cyclades, 

 or the shells of Dreissena and Cardium, as in the islets near 

 Astrakhan. It is believed to indicate the foi'mer 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 Caspian, 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 which 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. 



Few other inland bodies of brackish water are known to have 

 peculiar shells ; those of the modern deposits, in Mesopotamia 

 (at Sinkra and Warka), collected by Mr. W. K. Loftus, are 

 species still abounding in the Persian Gulf. All the living shells 

 of this Province are of estuary rather than marine character, 

 the so-called Rissoa being a Hydrobia, and the shell described b_y 

 H. Adams as Velutina Gasjnensis, a Limnsea Gebleri, Midd. 



VI. West African Province. 



The tropical coast of Western Africa is rich in conchological 

 treasures, and far from being wholly explored. St. Helena and 

 Ascension Island are included. About 300 species have been 

 obtained on the coast, and 150 species, mostly identical at 

 the Cape Verd Islands. The most characteristic genera are 

 Pleurotoma, Oliva, Marginella, Cymbium, Terebra, Pusionella, 

 Tj'mpanotomus, Mesalia, Ungulina, Felania, Tugonia, Talona, 

 Tellina. There are 40 species of Marginella, 36 of Plevirotoma, 

 20 of Tellina. Quite a number of the species cross the Atlantic, 

 recurring upon the opposite Brazilian and West Indian coasts. 



VII. South African Province. 



The fauna of South Africa, beyond the tropic, possesses few 

 characters in common with that of the western coast, and is 



