. College collection of palaeontology. AMPHIBIA. 61 Their form was usually salamandroid, the limbs weak aud tail long; some forms were probably serpent-like; none were frog- like, as formerly supposed. Many genera had large pectoral plates and a ventral armor of scales; and some had the head pro- tected with a helmet of bony plates. The skull varied in differ- ent genera from mucli elongated as in Archegosaurus, to short, as in Brachyops. The vertebrae were biconcave. Huxley enumerates thirtj'-eight undoubted genera, and fifteen which are questionable. No. 93. [293] Labyrinthodon (Mastodonsaur
. College collection of palaeontology. AMPHIBIA. 61 Their form was usually salamandroid, the limbs weak aud tail long; some forms were probably serpent-like; none were frog- like, as formerly supposed. Many genera had large pectoral plates and a ventral armor of scales; and some had the head pro- tected with a helmet of bony plates. The skull varied in differ- ent genera from mucli elongated as in Archegosaurus, to short, as in Brachyops. The vertebrae were biconcave. Huxley enumerates thirtj'-eight undoubted genera, and fifteen which are questionable. No. 93. [293] Labyrinthodon (Mastodonsaurus) Jaegeri, Owen. Head (cast). This is the largest l^nown Am- phibian species, having labyrinthine teeth, i. e., a convergence of numerous inflected folds of the external layer of cement tovpards the pulp-cavity. The form of the animal was salamandroid. The body equaled the largest crocodile in size and was protected beneath by bony plates and scales. The head was triangular; the nostrils very small; and the orbits situated nearly halfway between the fore and back part of the skull. In this specimen the skull and lower jaw are firmly closed. It was found in the Upper Trias (Keup- er), near Stuttgardt, Wurtemberg, and is in the Museum of that city. No. 94. [294] Cheirotherium Barthi, Kaup. Tracks, on slab, in relief (cast). These remarkable foot-marks strikingly resemble the impression of the human hand, whence the generic title (Hand-beast). The tracks of the hind foot are about eight inches long and five wide. Less than two inches in advance of them are the prints of the fore-feet, which are only four inches long and three wide. The footprints follow one another in pairs, about fourteen inches apart. Dr. Kaup, who first described these ichnites, conjectured that the animal might have been a large species of the Opossum; but in the didelphic quadrupeds the thumb is on the inner side of the hind-foot. Bones of Lahy- rinthodon have been found in the same locality as the footprin
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