■92 PROP. J. LOGAN LOBLEY, P.G.S., ETC.^ ON 



the rocks were formed during an epoch which has been 

 called " the Age of Reptiles "' from the dominance of the large 

 ■marine and the gigantic land reptiles which then peopled 

 the globe. The enormous and terrible Dinosauria is an 

 extinct order ot Keptilia ; — our present largest reptile, the 

 ■crocodile, having a femur only one-sixth the length of the 

 femur of a deinosaur. Another most remarkable extinct 

 order, the Pterosauria, flourished in Jurassic times. These 

 extraordinary creatures were winged reptiles, the wings 

 having a range of extension up to 24 feet. Al- 

 though the wings were bat-like and not feathered, the 

 pterodactyles had some of the characters of birds in 

 conjunction with some that were reptilian. The remains 

 -of a true feathered bird, however, have been found in 

 these rocks, showing that all the classes of Mammalia Avere 

 in existence in the Jm-assic epoch. 



One feature of the Secondary fauna is too remarkable 

 to be here omitted. It is the incoming, enormous develop- 

 ment of, and then the extinction of, two Avell defined groups 

 ■of the class Cephalopoda, the ammonites and belemnites. 

 Along with the ammonite flourished the nautilus, of the 

 same order of Cephalopoda, the Tetrabranchiata, yet iu 

 Palaeozoic times the nautilus lived when there were no 

 ammonites, and the nautilus still flourishes, while the 

 ammonite ceased to exist at the close of the Secondary epoch. 



With the exception of the Old Red Sandstone and the 

 tjoal seams with their underclays and shales, the rocks 

 known to us up to the Jurassic series are, from their fossils, 

 obviously marine. But some of the beds of the lower 

 oolites are estuarine in origin, and they contain a large 

 assemblage of land plants, in some cases beautifully 

 preserved, which alFord an indication of the character of 

 the terrestrial flora of Jurassic times. From these fossil 

 plants and parts of plants it is seen that this was an epoch 

 of gymnospermous phanerogams. The prevailing order 

 was Cycadaceae, about twenty genera of cycads having 

 been described from Jurassic rocks, and the conifers were 

 represented by the genera Araucaria, Pinites, Thuytes, and 

 others. 



The Cretaceous rocks furnish a most interesting connecting 

 link with the present, since their most remarkable division, 

 the chalk, is a rock of the same character and composition 

 as a deposit now forming on the floor of the Atlantic Ocean. 

 Even some of the species of the microscopic shells of which 



