On the Stagonolepis Robertsoni of the Elgin Sandstones. 75 



Stagonohpis into a reptile of high organization, though of nondescript 

 characters, did not interfere with his long-cherished opinion — founded 

 on acknowledged facts — as to the progressive succession of great 

 classes of animals, and that, inasmuch as the earliest Trilobite of the 

 invertebrate Lower Silurian era was as wonderfully organized as 

 any living Crustacean, so it did not unsettle his belief to find that 

 the earliest reptiles yet recognized, the Stagonolepis and Telcrpeton, 

 pertained to a high order of that class. 



3. " On the Stagonolepis Robertsoni of the Elgin Sandstones ; and 

 on the Foot-marks in the Sandstones of Cummingstone." By 

 Thomas H. Huxley, F.R.S., F.G.S., Professor of Nat. Hist., 

 Government School of Mines. 



The unquestionable remains of Stagonolepis Robertsoni which 

 have hitherto been obtained consist partly of bones and dermal scutes, 

 and partly of the natural casts of such parts. The former have been 

 obtained only at Lossiemouth, and are comparatively few in number ; 

 the numerous natural casts, on the other hand, have all been pro- 

 cured at the Findrassie Quarry, in which no bones or scutes, in their 

 original condition, have been discovered. 



The considerable series of remains exhibited to the Society did not 

 embrace all those which had been subjected to examination, but 

 contained only a selection of those more characteristic parts upon 

 which the conclusions of the author of the paper, respecting the struc- 

 ture and affinities of Stagonolepis, are based. 



They were — 1. Dermal scutes; 2. Vertebrre ; 3. Ribs; 4. Bones 

 of the extremities; 5. Bones of the pectoral arch; and 6. A na- 

 tural cast of a mandible with teeth. The dermal scutes are all 

 characterized by an anterior smooth facet, overlapped by the pre- 

 ceding scute, and by the peculiar sculpture of their outer surface, 

 which exhibits deep, distinct, round or oval pits, so arranged as to 

 appear to radiate from a common centre. Of these scutes there are 

 two kinds, the fiat and the angulated. By a careful comparison 

 with the dermal armour of ancient and modern crocodilian reptiles, 

 it was shown that every peculiarity of the scutes of Stagonolepis 

 could find its parallel in those of Crocodilus or Teleosaurus, — the flat 

 scutes resembling the ventral armour of the latter, the angulated 

 scutes the dorsal armour of the former genus. 



An unexpected verification of the justice of this determination 

 was furnished by a natural cast of a considerable portion of the 

 caudal region of Stagonolepis, consisting of no less than seven ver- 

 tebrae, enclosed within the corresponding series of dermal scutes. 

 Of these, the dorsal set were angulated ; the ventral, flat. 



It would appear that the anterior dorsal scutes attained a very 

 considerable thickness, while the posterior scutes were widest, 

 attaining more than five inches in Ijreadth in some instances. 

 The 'vertebrae dcF.ribed were all studied from natural casts, and 

 belonged to the caudal, sacral, and anterior-dorsal series. These 

 vertebra; are, in their leading features, similar to those of Teleosau- 



