THE GEOLOGICAL RECORD 197 



then by reptiles, the last being the highest life forms present in the 

 Palaeozoic rocks. The vegetation is confined at first to crypto- 

 gams, but towards the end of the Era gymnosperms have made 

 their appearance. It is a remarkable fact that representatives of 

 all the invertebrate sub-kingdoms have been found in the earliest 

 Palaeozoic rocks, appearing, it is true, in rudimentary forms, 

 but still with a considerable amount of specialisation. This points 

 to the existence of many yet undiscovered faunas in the Eozoic 

 rocks. Vast numbers of genera and even whole classes appeared 

 and became extinct within the Palaeozoic Era. For instance, the 

 graptolites, blastoidea, cystidea, trilobites, and armoured ganoids 

 flourished and became extinct. Others, like the merostomata, 

 the rugose corals, the spire-bearing brachiopods, the articulated 

 echinoidea, and the nautiloid cephalopods, flourished in great 

 numbers and died down later to small numbers of degenerate 

 forms. 



Neozoic life is at first characterised by abundance of reptiles, 

 and afterwards by abundance of mammals. The reptiles occupied 

 the sea, the land, and even the air. The mammals give the best 

 evidence of evolution and progressive specialisation hitherto 

 obtained from the rocks. The abundant brachiopods are gradually 

 replaced by lamellibranchia, holostomatous by siphonostomatous 

 gastropods, regular by irregular echinoidea, the reptile-like 

 birds of the Mesozoic by the normal types of the Cainozoic. 

 Cycads and conifers give place to angiosperms, cartilaginous to 

 teleostean fishes. But again, many forms, either originating during 

 the Era or surviving from the preceding Era, flourish exceedingly 

 and then diminish or die out. Thus the ammonites and belemnites 

 among the cephalopods, the nummulites among the foramini- 

 fera, the hippurites among the lamellibranchia; the dinosaurs, 

 ichthyosaurs, and plesiosaurs among the reptiles ; the creodonts 

 and dinocerata among the mammals become wholly extinct, 

 while the mud fishes, terebratulae, trigoniae, nautili, the edentata, 

 and the marsupials have all become vastly reduced in numbers 

 and importance at the present day. On the other hand, the snakes 

 and turtles, the apes and herbivora, the birds, the dicotyledons 

 and grasses, the lamellibranchs and gastropods, increase in pro- 

 portion as the others diminish. 



