A little more than ten years ago, namely, on the 15th December 1858, Sir R. Murchison read a paper “On the Sandstones of Elgin” before this Society. It was followed by an essay of my own “On the Stagonolepis Robertsonii ,” an animal so named by Prof. Agassiz in his ‘Poissons fossiles du Vieux Gès Rouge’ from some impressions of its dermal covering which had been discovered in the Elgin sandstones. In the latter paper, and in notes added to both papers, before their publication in the middle of the following year, the fact that Stagonolepis was a reptile closely allied to the Mesozoic Crocodilia , though distinct from any known form of that age, was for the first time asserted, and, indeed, I may say, demonstrated, the remains placed in my hands enabling me to put the fact beyond doubt. At the same time I mentioned the existence in the same beds of “a Saurian reptile about 6 feet long, remarkable for the flattened or slightly concave articular surfaces of the centra of its vertebræ, and for its well-developed costal system and fore and hind limbs, but more particularly characterized by its numerous series of subcylindrical palatal teeth.” I named this new reptile Hyperodapedon Gordoni , in honour of its discoverer, the Rev. Dr. Gordon, to whose exertions in the Elgin country geology owes so much: and I stated that “its marked affinity with certain Triassic reptiles, when taken together with the resemblance of Stagonolepis to Mesozoic Crocodilia , lead one to require