FOSSIL TURTLES. The origin of the Chelonia is uncertain. Otoecelus, all armored eotylosaur from the Permian of Texas, has been suggested by Cope as a possible progenitor, but the relationship is extremely doubtful. Certain characters of shoul der-girdle and ventral abdominal ribs in the plesiosaurs indicate that this order may have genetic affinity with the turtles, and the dicy nodonts and plaeodonts of Triassic age resemble turtles remarkably in many structures of the skull and limb-bones. (See TIIEROMORPIIA.) All these groups belong to the synapsid division of Reptilia. Little evolution is demonstrable within the ehelonian order from its first appearance in the European Upper Trios to the present. except in the degeneration of the carapace and elongation of the digits in the marine forms. The oldest turtle known is Proganoehelys, from the Royer (Upper Trios) of Germany. A probably' primi tive character in this genus is the well-developed row of supra-marginal plates. The Lower Juras sic strata have, as yet, yielded no chelonian re mains. hut in the Upper Jurassic, Cretaceous, and the Tertiary they are abundant. chiefly in the Northern hemisphere. The existing suborders Cryptodira and Pleurodira appear to be fully differentiated in the Upper durassie, the Trimly ehia in the Upper Cretaceous of North America. As a rule the known Jurassic turtles, have a solidly roofed skull like that of the recent green turtle, and a well-developed carapace. Professor Banes opinion is that the earliest turtles were swamp-turtles, and that the soft-shelled Trimly chin and the marine families evolved from these along one line, and the hand tortoises along an other.
Cryptodira is the suborder most widely represented among fossils, as among recent tur ties. Several of the existing families, including the marine Chelonithe and the 'leather-turtles,' are already differentiated in the Cretaceous, and in the Lower Eocene the highly specialized land-tortoises appear. Of the Cretaceous sea turtles some attained enormous size: Protosphar gis from Italy had a shell nine feet long, and in the North American Archelon the skull alone measures three feet. The suborder Pleurodira is widely distributed as fossils in various Meso zoic systems. Miolania, from the Pleistocene of Queensland, was a huge creature in which the head was armed with bony 'horns.' The third suborder, Trionyebia, is known from the North American Cretaceous and the Tertiary of both hemispheres. The gronp shows scarcely any change from its first appearance to the present.
13IBLIOGRAPuY. Consult standard works and au thorities cited under RErrii.E and ToRTOISE; Bontenger, Catalogue of CheIonians in British Museum (London, 1889) ; Gadow, Amphthia and Reptiles (London, 1901) ; L. Agassiz, Contribu tions to the Natural history of the United States (Boston, 1857). Most of the literature on fossil Chelonia consists of special papers in scientific periodicals. The most important ones are by G. Banr and E. Fraas in Germany, Boulenger and Gadow in England, and 0. P. Day in America.