TURTLES. 313 



KEPTILES. 



Chelonia. The total number of known species of chelonians is 

 estimated by Hoffmann (1880) to be somewhat more than two hun- 

 dred and fifty. Of these only five are marine forms, the rest being 

 inhabitants of the land and its fresh waters. The former, com- 

 prised in the genera Dermatochelys (or Sphargis), Chelone, and 

 Thalassochelys, are very broadly distributed throughout the tropi- 

 cal and sub-tropical or temperate waters of both the Old and the 

 New World, most of the species being cosmopolitan, or nearly so. 

 Dermatochelys coriacea, the leathery turtle, is found along the 

 American border from Brazil to South Carolina and Massachusetts, 

 exceptionally on the European coast, and in the Indian and Pacific 

 oceans, from Africa to Chili. The green turtle (Chelone viridis), 

 which is held in such high estimation as an article of food, has an 

 equally extended range, although it is but very rarely found on the 

 European coast (England to the Mediterranean). Of still rarer oc- 

 currence in the European seas is Chelone imbricata, the hawk's 

 bill, which yields the tortoise-shell of commerce, and whose habitat 

 embraces nearly the whole circumference of the globe. The log- 

 gerhead (Thalassochelys corticata) is abundant on both sides of the 

 Atlantic, and in the Mediterranean, and is at rarer intervals also 

 met with in the Indo-Pacific basin. 



The land and fresh- water chelonians have a very unequal dis- 

 tribution, being most abundant in the region of the tropics, and 

 rapidly diminishing as we pass either north or south into the tem- 

 perate zones. The greatest number of forms belong to tropical and 

 sub-tropical America, and the smallest number to Australia and 

 temperate Eurasia, each of which possesses some fifteen species. 

 The northern limit reached by these animals in the Western Hemi- 

 sphere is about the fiftieth parallel of north latitude (Chelydra 

 serpentina), and not improbably the same parallel marks the cor- 

 responding general limit in the Eastern Hemisphere, although in 

 Europe Cistudo lutaria or Europaea, the most wide-spread species 

 of the continent, is found as far north as the fifty -fourth parallel 

 (Mecklenburg), and possibly still farther. The total number of 

 European species is five, most of which more properly belong to 

 the region about the Mediterranean. No species is known from 

 Great Britain, the Scandinavian Peninsula, Denmark, Holland, or 



