58 EXTINCT MONSTERS 



the world's history known as the Silurian and the Old Eed 

 Sandstone periods. As far as we know, they did not survive 

 beyond the succeeding period, known as the Carboniferous. 1 



1 The student should consult Dr. Henry Woodward's valuable Monograph 

 of the British Merostomata (Palseoutographical Society), to which the writer is 

 much indebted. With regard to the representation of Pteryyotus anglicus in 

 Plate II., it has been pointed out by Dr. Woodward that the creature was unable 

 to bend its body into such a position as is shown there. As in a modern 

 lobster or shrimp, there were certain overlapping plates in the rings, or 

 segments, of the body, which prevented movement from side to side, and 

 only allowed of a vertical movement. 



