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 

 footprints ; and it is now regarded as certain that the 

 Cheirotherian tracks are those of Labyrmthodont Am- 

 phibians. This specimen, discovered in the New Red 

 Sandstone (Lower Trias) at Jena, Germany, belongs to 

 the Ward Collection in the University of Rochester. 



Size, 7 ft. 2 in. x 18 in. 



