450J AMERICAN TESTUDINATA. Tart II. 



scribed within as naiTOw limits as any other type of animals. It has already been 

 stated, (p. 301,) that there is a great difference between the geographical distriljntion 

 of the Sea Turtles and that of the fiuviatile and terrestrial species of this order. 

 There are, in flict, only two marine Fauna3 of Testudinata, — that of the Atlantic 

 Ocean, and that of the Pacific, including the Indian Ocean ; and between the two 

 there exist only specific differences between their representatives, the genera are 

 the same. In the Atlantic Faunte we have four species along the American coasts : 

 Sphargis coriacea, Thalassochelys Caouana, Chelonia Mydas, and Eretmochelys imbri- 

 cata; while in the Pacific Fauna only one species, the Chelonia virgata, has thus 

 far been noticed along the western coast of America. 



Among the fresh-water species there are two, Chelydra ser2Dentina and Ozotheca 

 odorata, which extend nearly over the whole range occupied by Testudinata, east 

 of the Rocky Mountains. Thyrosternum pennsylvanicum is also very widely dis- 

 tributed ; and so is Malacoclemmys palustris ; but this last occurs only in saltrmarshes 

 along the sea-shores from New York to Central America. All the other species 

 have a more or less circumscribed home; so that the whole country may be divided 

 into a number of very natural Chelonian Faunae, according to their distribution. 



1st. The North-eastern Fauna. It extends as far north and east as Turtles occur, 

 that is, through parts of Nova Scotia, New Brunswick, and Canada West, a little 

 beyond the forty-fifth isotherm. Westward it reaches Lake Erie, and southward 

 North Carohna, extending along the AUeghanies even as far south as Georgia. Its 

 boundaries coincide with those of Chrysemys picta. It is chiefly characterized by 

 Clemmydoida?, three distinct genera of which occur within its area : Nanemys 

 guttata, which, like Ch. picta, ranges through its whole extent, with the exception 

 only of its most north-eastern parts; Glyptemys insculpta, which is found from the 

 most northern to the middle regions of the Fainia; and Calemys Miihlenbergii, which 

 occurs only in the middle region. Ptychemys nigosa is characteristic of the borders 

 of the Chesapeake Bay. Cistudo virginea is found everywhere, but sparingly in 

 the northern range ; while it extends very far westward and southward, where it is 

 most common. Chelydra serpentina and Ozotheca odorata also occur everywhere, 

 while Thyrosternum pennsylvanicum begins to appear in its middle tracts onl}". 

 Along the sea-shores, Malacoclemmys palustris begins also in the middle region of 

 the Fauna; but it is nowhere found in the interior, far from salt water. Emys 

 Meleagris, which is characteristic of the north-western Fauna, is rare here, and so 

 also is Graptemys geographica. On the western borders of this Fauna, Aspidonectes 

 spinifer begins to make its appearance ; but there is no trace anywhere of the 

 family of Testudinina. 



2d. The Wedern Fauna. This Faima extends westward from the western parts 

 of Pennsylvania to the arid plains at the foot of the eastern slope of the Eocky 



