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188 highly specialized species, the astragalo-calcaneum and the large, hemispherical fourth tarsale, articulating together enarthrodially, around which all the short metatarsals closely articulate in two groups of two and three.



. 154. Limbs and feet of Chelonia. Natural size. A, Chrysemys, hind leg from postaxial side. B, Chrysemys, front foot, dorsal side. C, Chelydra, hind foot, dorsal side. D, Cistudo, hind foot, dorsal side. E, Podocnemys, left hind leg, postaxial side. F, Podocnemys, right front forearm and foot, dorsal side. G, Trionyx, left hind foot, dorsal side.