MARINE PROVINCES. 161 



The Mediterranean fauna appears to be perfectly homogeneous ; 

 but a few African forms enter the Straits of Gibraltar, and are 

 found on the adjacent coasts of Spain and Algiers. The most 

 peculiar of these species is the large Gymbaim olia^ belonging to 

 the family Volutidte. 



In the Bay of Cadiz, just without the Strait of Gribraltar lives 

 the Halia priamus^ the only representative of its genus. Its 

 position in the system has been often changed, and it is only 

 within late years that the animal has been obtained and its 

 relationships understood. It is extinct in the Mediterranean, 

 but fossil in the pliocene of the North of Italy. Ungidina ruhra^ 

 of Senegal, has likewise been collected at Cadiz. Strombus 

 bubonius of Senegal is found fossilized in the latest deposits of 

 the newer pliocene. 



The study of the miocene and pliocene tertiary fauna of the 

 Mediterranean Countries shows that this Sea has received acces- 

 sions belonging to the Indian Ocean, West Africa and North 

 Europe. These tertiary fossils appear to indicate a much warmer 

 sea, in which Polyps lived. Consequent upon its refrigeration and 

 the interruption of the communication with the Indian Ocean, a 

 number of these genera became extinct at the commencement of 

 the pliocene epoch, although a few representatives of a more 

 tropical fauna still survive. The following may be cited : 



{A, African; 0, Indian Ocean). 



Umbrella, 0. Fasciolaria, A. Mesalia, A. 



Marginella, A. Cancellaria, A. Clavagella, 0. 



Cymbium, A. Pedicularia, O, Cardita, A. O. 



Clanculus, A. 0. Sigaretus, A. Chama, A. 0. 



Xenophora, A. 0. Siliquaria, A. Spondylus, A. 0. 

 Typhis, A. 0. 



Finally the Mediterranean genera Crepidula, Smaragdia, 

 Dolium, Rissoina, Solemya, Thecidium, are identical with 

 American forms belonging to the Transatlantic and Carib- 

 bsean Provinces. 



Black Sea. In the northern part a few Aralo-Caspian shells 

 are found, otherwise the Black Sea only ditters from the Medi- 

 terranean in the paucity of its species ; Dr. Middendorfl' enumer- 

 ates 68 only. The water is less salt, and there is no tide, 

 but a current flows constantly through the Dardanelles to the 

 Mediterranean. 



Gulf-weed Banks. The few species collected are principally 

 pelagic, consisting of nudibranchiates, Litiopa, etc. Two species 

 of Patellidae are the only mollusks in common with Europe and 

 there is no good reason why this fauna should be included in the 

 Lusitanian Province. 



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