224 LITTORAL DISTRICTS. 



expect to find as great a number of different belts of organized beings as we 

 find on land as we rise in altitude or in latitude. The tabulation of the 

 range of the species thus far found in Florida shows a very wide range in 

 (height) depth, in a comparatively narrow belt of variation of tempera- 

 ture. The species which characterize a local fauna are very limited 

 in depth, while, as a general thing, they have a wide geographical distri- 

 bution, as will he seen by an examination of the species which eminently 

 characterize the littoral fauna of the West Indies or of the West Coast of 

 Europe, which very soon merge (alter two or three intermediate belts) into 

 the deep-water (cold area) fauna of the North Atlantic. The species char- 

 acteristic of the deep waters of Florida, thus far not found extending to the 

 other side of the Atlantic, are Coelopleurus lloridanus. Salenia varispina, Podo- 

 cidaris sculpta, Trigonocidaris albida, Echinus gracilis. Echinolampas depressa, 

 and Agassizia excentrica. Of the truly littoral species of the Tropical At- 

 lantic District, some of them range from North Carolina, and even New 

 Jersey and Long Island Sound, to the southern extremity of Brazil; a great- 

 er number extend from South Carolina to Brazil ; a still greater number from 

 Florida to Brazil ; while from Florida to the northern part of Brazil we find 

 the strictly West Indian fauna (Tropical Atlantic District) sending out its 

 feelers to the Mediterranean, to the Platte River, to the Bermudas, and to 

 the West African Coast, while some of the deep-water (cold area) species are 

 found in the Gulf of St. Lawrence, the Azores, Shetland Islands, Mediterra- 

 nean, and West Coast of Norway. Two species, Encope Michelini and Moira 

 atropos, seem to be specially characteristic of the mainland, and thus far ex- 

 tend but a short distance south from Mexico. ^nA do not reach farther north, 

 the one than the Florida Keys, the other than North Carolina ; they are on 

 that part of the coast always accompanied by Arhacia punctulata. which thus 

 far has not been found in the West Indies, except on the coast of Cuba and 

 in the Straits of Florida. 



The American North Atlantic Coast from New Jersey to Hudson's Bay is 

 inhabited by species belonging in part to the North Atlantic District (PI. JJ) 

 and the Boreal American (PI. A), and in part to the Tropical Atlantic District 

 (PI. A). One of the species, Echinarachnius parma. is found not only on the 

 Atlantic side of America, but extends from the Straits of Behring along the 

 Aleutian Islands and on the Pacific Coast as far south as the East India Isl- 

 ands. Of the Tropical Atlantic species. Arhacia punctulata extends 

 to the southern extremity of Cape Cod ; this is also the limit of Mel- 



