THE RECORD FROM FOSSILS. 95 



been found to be slowly developing during its prog- 

 ress. Before, or during the Silurian age, all of the 

 sub-kingdoms of animals came into existence. 

 Ccelentera were present in the shape of sponges, 

 corals, hydroids. Among Echinodermata were found 

 crinoids, star-fishes, and some extinct forms of sea 

 urchins. Various mud tracks tell us that marine 

 worms lived in these early mud flats. Mollusks 

 were abundant, some related to clams and oysters 

 (lamellibranchs), and others related to our snails 

 and cuttle-fishes. Brachiopoda existed in marvellous 

 numbers, and the closely allied Bryozoa were plenty. 

 Crustacea there Avere, much like our shrimps and 

 lobsters, and a special type (trilobites) was highly 

 characteristic of the age. Scorpions were present 

 to represent the air-breathing animals, and the exist- 

 ence of their sting tells us that other air-breathing 

 animals (probably insects of some kind) had also 

 appeared. Of the sub-kingdom Vertebrata the 

 indications are scanty, though there is no doubt that 

 they were in existence by the close of the Silurian 

 age, for in the upper rocks of that period unques- 

 tionable fossil evidence has been found, and recent 

 discoveries have shown them in the lower Silurian 

 rocks, thus carrying them almost to the bottom. 

 The earliest vertebrates could not have had any 

 hard parts to be preserved, true bones and even 

 cartilage being of more recent origin, and this 

 explains their scanty remains in the lowest rocks, 

 although there can be no doubt that the vertebrates 

 must have been more or less abundant even in the 

 lower Silurian times. 



