Ch. XXVI] FOSSIL FOOTPKESTTS OF " OLD BED." 



413 



The matrix is a fine-grained whitish sandstone, with a cement of carbon- 

 ate of lime. Although almost all the bones except those of the skull 

 have decomposed, their natural position can still be seen. Nearly perfect 

 casts of their form were taken by Dr. Mantell from the hollow moulds 

 which they have left in the rock. 



Slight indications are visible of minute conical teeth. Of ribs there 

 are twenty-four pairs, very short and slender. The pelvis is placed after 

 the twenty-fourth vertebra, precisely as in the living Iguana. On the 

 whole, Dr. Mantell inferred that the animal possessed many Lacertian 

 characters blended with those of the Batrachians. He was unable to 

 decide whether it was a small terrestrial lizard, or a freshwater Batrachian, 

 resembling the Tritons and aquatic Salamanders. 



Although this fossil is the most ancient quadruped of which any 

 osseous remains have yet been brought to light, it seems not to have 

 been the only one then existing in that region, for Captain Brickenden 

 observed, in 1850, on a slab of sandstone from the same quarry at Cum- 

 rningstone, a continuous series of no less than thirty-four footprints of a 

 quadruped. A small part of this track, the course of which is supposed 

 to have been from a to b, is represented in the annexed cut (fig. 537). 

 The footprints are in pairs, forming two parallel rows ; the hind foot being 



Fig. 537. 



Scale one-sixth the original size. 



Part of the trail of a (Chelonian ?) quadruped from the Old Bed Sandstone of Cum- 

 mingstone, near Elgin, Morayshire. — Captain Brickenden. 



one inch in diameter, and larger than the fore foot in the proportion of 4 

 to 3. The stride must have been about 4 inches. The impressions re- 

 semble those left by a tortoise walking on sand ; and, if this be the 'true 

 interpretation of the trail, they are the only indications as yet known of a 

 chelonian more ancient than the trias. 



I have already alluded (p. 400) to trails referred by American geolo- 

 gists to several species of air-breathing reptiles, and discovered on the 

 eastern flank of the Alleghany range, in Pennsylvania, in a red shale, so 

 ancient that a question has arisen whether the rock should be classed as 

 the lowest member of the carboniferous, as Professor H. D. Rogers con- 

 ceives, or as the uppermost Devonian, as some have contended (see p. 400). 

 They at least demonstrate that certain quadrupeds, of larger size than 

 any of the bones that have been found in carboniferous rocks, existed at 



