MARINE RELICTS; BIPOLAR FAUNAS 1065 



three fish, and one seal {Phoca annellata Nilss). The Crustacea 

 are especially interesting. Mysis oculata Fabr. var. relicta is the 

 most widely distributed type. It is a variety of a true marine 

 form which occurs in the northern seas on the coast of Labrador" 

 and Greenland. The same variety occurs in lakes Superior, Michi- 

 gan, and Ontario, in the Gulf of Bothnia, and in the Caspian Sea. 

 The other marine Crustacea of the Scandinavian-Finnish seas are 

 three amphipods ; one isopod, one phyllopod, and one lophyropod. 



Relict seas derived from the shrinking of former mediterraneans 

 are found in the Caspian and Aral seas, which are still shrinking. 

 These seas are fragments of a once extensive southeast European- 

 Asiatic mediterranean of later Tertiary time (Sarmatien). The 

 relict fauna of the Caspian includes, besides the seal {Phoca cas- 

 pica), sixteen species of molluscs, including Cardium, Adacna, 

 Venus, etc. ; two Crustacea, four sponges, and a number of fish. 

 These seas are further characterized by having salty or brackish, 

 instead of fresh, water. 



Marine Relicts — Bipolar Faunas. "Bipolarity in the strict 

 sense," says Ortmann, "f. e., the presence of an identical species at 

 the North and South Poles, while it is absent in the intermediate 

 regions, is extremely rare, and there are hardly any well-established 

 cases. Bipolarity in a wider sense — presence of closely allied spe- 

 cies at the poles, while in the intermediate regions allied forms 

 are absent — is a well-established fact." The known cases are chiefly 

 of pelagic animals. Ortmann thinks that, in some cases, as medu- 

 sae, pteropods, and tunicates, the ancestors lived in the tropical 

 seas of Tertiary time, and their descendants migrated both north 

 and south, the tropical forms subsequently becoming extinct. The 

 difference between the north and south polar types in other cases 

 is explained by Ortmann as due to dififerent sources of the migrants, 

 the Arctic faunas being derived from the old Mesozoic Mediter- 

 ranean waters, and the Antarctic from Pacific waters. Other ex- 

 amples of marine relicts, or the occurrence of faunas in basins of 

 the sea, while they have become extinct in the neighboring region, 

 is shown by the fauna of Quahog Bay near Portland, IMaine ; and 

 in the southern parts of the Gulf of St. Lawrence, as about Prince 

 Edward's Island, and the op])osite coast of Nova Scotia, where the 

 water is shallow and much warmer than on most parts of the 

 Maine coast. Here Venus rnerccnaria is found in some abundance, 

 associated with oysters and other southern species which are absent 

 from the New England coast. They constitute "a genuine southern 

 colony, surrounded on all sides, both north and south, by the 

 boreal fauna." (\'errill and Smith-54 :?(5o.) 



