10 PAST AND PRESENT FORMS OF LIFE 



preserved in sedimentary beds than those of minute 

 organisms, they are also less likely to be overlooked when 

 exhumed in the operations of human industry. Take 

 as an example the chalk-beds of Great Britain, and, 

 among these, the Senonian beds, that massive formation 

 which is two hundred and sixty-five feet deep at Margate. 

 The whole of this is pure chalk, composed almost entirely 

 of the shells of myriads of microscopic animals classed 

 as Foraminifera, which co -existed with mighty Deino- 

 saurs, Ichthyosaurs, and Mosasaurs, some of which have 

 been found of a length of seventy-five feet. Even less 

 fitted than these fragile shells for preservation through 

 innumerable aeons are the delicate forms of insect life; 

 yet these have been identified in beds far older than the 

 chalk, the most ancient known insects having been dis- 

 covered in Devonian rocks of New Brunswick. Some of 

 these certainly were designed on heroic lines, one being 

 an ephemerid or May fly, with a wing spread of five 

 inches; and the carboniferous beds of Canada, younger 

 than the Devonian, have preserved a still nobler May 

 fly, measuring no less than seven inches across the wings. 

 Scorpions of gigantic size, as well as spiders, cockroaches, 

 and beetles of ordinary stature, have been found in the 

 same formation. Among the Jurassic rocks of the Lower 

 Lias occur bands so densely filled with flies and beetles 

 that they have come to be known as the Insect Beds. 

 Upwards of one hundred distinct species of beetles have 

 been identified among them, and several species of 

 midges and gnats. Coming down to the Tertiary period, 

 amber, the fossil resin of submerged forest, has preserved 

 myriads of the most delicate forms of insect life, which 

 flitted through forests tenanted by such gigantic creatures 



