204- WALTER KIDD, M.D., P.Z.S., ON 



and mollusca, for example, now reached their zenith with 

 ammonites and belemnites. On land appeared butterflies 

 and various insects, enormous amphibians, true reptiles, huge 

 dinosaurs, crocodiles, winged reptiles, small mammals of 

 marsupial type, and a few birds. The earliest leaf-bearing 

 plants also came forth. In this period again, as with the 

 invertebrate fauna of Silurian times, all vertebrates with 

 their five orders were represented. And how were these 

 new denizens, many of them appearing suddenly U])on the 

 scene of life, greeted in the home where they found them- 

 selves ? There were warmth, excessive moisture, equabilit} 

 of conditions provided for this exuberant vegetable and 

 animal life, and as in other times scope for expansion rather 

 than struggle for existence, according to Sir William Dawson, 

 was the order of the day. Increasing definition of land and 

 sea Avhich began in Palaeozoic, continued slowly through 

 this Mesozoio period, and took its more modern form in 

 Cainozoic times, and slow development of climatic conditions 

 ensued. During this age the great chalk formations of the 

 world Avere being laid down in the sea for immense periods 

 of time, constructed from the minute shells of foraminifera, 

 and the flint from innumeiable polycystina, spicules of 

 sponge and diatoms ; these tiny creatures subserving the 

 Design prevailing through all geological time, which could 

 anticipate the day of Man's growing ability to make use of 

 these stores of flint and chalk. At the close of this long 

 stretcli of time, in which the British seas were warm 

 enough for coral reefs and the Arctic Zone for great reptiles, 

 a period of much greater cold prevailed. At any rate this 

 is presumed as the only known reason for that remarkable 

 extinction of species which took place over the large con- 

 tinents, when the giant forms of the Age of Reptiles largely 

 disappeared. The cold termination of the Secondary period 

 served its purpose in preparing the way for a higher scale 

 of life on land and sea. The birds and mammals, which 

 in secondary times had been represented in low and less 

 perfect forms, became highly specialized as the great colossi 

 of Saurian type gave way to their nobler if Aveaker suc- 

 cessors, and the Cainozoic became the Age of Mammals. 

 The new order of creatures of this important epoch were 

 again gently dealt with by a supreme Intelligence. The 

 fresh outburst of vertebrate life, and forests with large 

 proportion of warm-climate types, were not at once sub- 

 jected to that severity of condition which closed the 



