HORTON — GEOLOGY OF THE STONESFIELD SLATE, 



257 



reptiles tlie Pterodactyles are represented by one species (P. Buck- 

 landi), cliiefly known by its wing-bones, remarkable for tbeir length, 

 and wMcIl, like those of birds, were hollow in the middle, thias com- 

 bining extreme lightness with strength. The family of turtles are 

 known in these beds by one small species of Glielonia. 



The remarkable catalogue of associated life exhibited by these rocks 

 is rendered still more complete by the occurrence of three genera of 

 Mammalia, namely, Anvphitherium, Phascolothermm, and Stereognathus. 

 Of these the only known remains are a few specimens of the lower jaws, 

 with small cuspidated teeth, indicative of a small insectivorous quad- 

 ruped, probably allied to the opossums, and other marsupial genera 

 now confined to Australia and Tasmania. It is extremely interesting 

 to observe that this resemblance to existing forms of Australian life is 

 by no means limited to the mammalia of the Oolite. For instance, 

 in the Australian sea exists the Gestracion PhilU]ji, or Port Jackson 

 shark, the only known representative of the numerous species of 

 Acrodi and Strophodi, the palatal teeth of which are so abundant in 

 the Oolitic beds. There also living Terebratulae are found associated 

 with a species of Trigonia, the extinct forms of which are among the 

 most common of the Stonesfield fossils. On the continent of 

 Australia also flourish the Araucarise and Cycadacese, coniferous 

 plants, very nearly allied to the vegetable remains of the Stonesfield 

 Slate. 



If we review the fossil treasures of Stonesfield in the aggregate, we 

 can to some extent reproduce that period of the earth's history in 

 which the district under our notice was a lagoon with boidering 

 marshes, intervening between a line of coast on the one hand, and 

 the ancient Oolitic ocean on the other. Every circumstance con- 

 nected with these finely laminated and ripple-marked sandstones 

 indicates the nature of the process by which they were deposited 

 to have been slow and gradual, doubtless demanding similar con- 

 ditions to those which would prevail in a shallow sea-lake, pene- 

 trated at intervals by moderate swells, or gentle tides from the 

 sea, but not exposed to storms or fluctuations caused by violent 

 littoral action. 



We may picture to ourselves the inhabitants of this lagoon, consti- 

 tuting a large population, beautiful branching star-corals analogous to 

 those forming the reefs and islets on which the broad Pacific smiles, 

 aristocratic Nautili and Ammonites associated with their humbler 

 neighbours, the Trigonise, Terebratulae and oysters that furnished a 

 supply of food for the numerous sharks and other predaceous fishes 

 infesting the wide open sea, and frequently visiting this quiet lake in 

 quest of prey. On the ancient land lived that monstrous reptile the 

 Megalosaurus and the crocodile-like Teleosaurus, with a few turtles ; 

 strange winged lizards, the Pterodactyles, hovered in the air, or 

 snatched their prey from the calm waters below ; and insects like 

 dragon-flies flitted over the reedy marshes. From time to time 

 fragments of bordering plants floated in the shallow pools, 

 either swept down by inundations or driven by the wind ; 

 VOL. III. 2 K 



