. Annual report. 1st-12th, 1867-1878. Geology. G48 GEOLOGICAL SURVEY OF THE TERRITORIES. KUMIXASTIA. EqUUS. Hy^na. SiMiUJE. Tragulus. Hipparion. Elefhas. ? PiNNIl'EDIA. FELIS. Ganis. Hv<eriiodon. Uusus. Nasua. Cebus. Anoplotbcrium. Anchitherium. Dinotherium Hapale. Omxivoua. Orohippus. Eofcasileus. Lemuk. Synoplathorium. Cercoleptes. / Bathmodon. ? Oligotomus. : Note.—Recent genera in shall capitals ; Miocene in italics,- and Eocene in ronian. Oh the plnjlogeny of the (jenerd of Tcstudinata.—The extinct tortoises of the Cretaceous and Eocene throw conside
. Annual report. 1st-12th, 1867-1878. Geology. G48 GEOLOGICAL SURVEY OF THE TERRITORIES. KUMIXASTIA. EqUUS. Hy^na. SiMiUJE. Tragulus. Hipparion. Elefhas. ? PiNNIl'EDIA. FELIS. Ganis. Hv<eriiodon. Uusus. Nasua. Cebus. Anoplotbcrium. Anchitherium. Dinotherium Hapale. Omxivoua. Orohippus. Eofcasileus. Lemuk. Synoplathorium. Cercoleptes. / Bathmodon. ? Oligotomus. : Note.—Recent genera in shall capitals ; Miocene in italics,- and Eocene in ronian. Oh the plnjlogeny of the (jenerd of Tcstudinata.—The extinct tortoises of the Cretaceous and Eocene throw considerable light on the probable origin of various existing genera,* and while much remains obi'cure, the following observations may be derived from the study of the forms in question: The order makes its appearance in the Triassic period, for I am as- sured by Dr. F. Endlich, of Reading, Pennsylvania, that the species obtained by Professor Queustedt in Wiirtembnrg belong undoubtedly to the Testudinata. With their special structure we are not yet fully acquainted. A number of genera appear in the Jurassic, and there is a successive increase in the number of species in the Cretaceous and Tertiary formations. Three structural features of importance mark the earlier fornSs. First, the incomplete union and ossilication of the ele- ments of the plastron and carapace; second, the reduction in size of the lobes of the plastron; third, the natatory character of the {)ha- langes, by their truncation and union in a single plane. Genera, re- taining some or all of the peculiarities, persist to the present day; but the ossified types, with distinct digits, are far more abundant, and are comparatively rare in the })eriod of the Jura. 8i)hargis, which is with- out carapace and has a greatly reduced plastron, may be regarded as nearest the primitive types of the order, though it still exists. Protoa- tega, of the Kansas Cretaceous, is its nearest extinct ally known. Fro- tostega is sui)erior i
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