DESCRIPTION OF AN EXTINCT PALiEOZOIC INSECT. 



53 



In this little oasis at St. John which formed a refuge for the 

 air-breathers of Silurian time, there no doubt was a much greater 

 variety of animals than we know of at present, but it is ques- 

 tionable whether a single vertebrate of the land was then in 

 being, and it is quite sui-e that none has been recovered. Verte- 

 brates, in the form of small mailed fishes, were living in the 

 estuaries around the borders of the land, but probably none were 

 adapted for locomotion over a dry surface, and so we have no 

 terrestrial vertebrates in the Silurian age. 



The bulk of the land fauna consisted of air-ljreathing articu- 

 lates, some of which are of novel and bizarre types, others like 

 forms found in the Coal Measures, but all widely divergent from 

 any living types. 



The large proportion of millipedes and centipedes is remark- 

 able ; they form a quarter of the fauna, are mostly of large size, 

 and several of the genera are like those of the Coal Measures. 

 If we had not these genera to supply intermediate links no one 

 would recognize in the Arachnoids, the scorpions and spiders of 



modern times. We have 



attempted a restoration of 



one of the forms related to 



the spiders on the basis 



of the specimen preserved, 



and of some Carboniferous 



forms described by Dr. S. 



H. Scudder. The way in 



which the thorax grades 



into the abdomen, though 



seen to some extent in 



the Carboniferous forms, is 



more complete in those of 



the St. John beds. 



An order of insects which is insignificant in the modern 



world — the Thysanura — had a larger proportion in this ancient 



fauna. These insects, by their want of wings, the absence of a 



distinct division of the body into three regions, and the unifor- 



Fig. 1. 

 EcRYMARTus LATus. Mag. 4. Restored. 



