288 THE OLDEST AIR-BREATHERS 



INVERTEBRATE AIR-BREATHERS. 



The coal formation rocks have afforded Land Snails, Milli- 

 pedes, Spiders, Scorpions and Insects, so that all the great 

 types of invertebrate life which up to this day can live on land 

 already had representatives in this ancient period. Some of 

 them, indeed, we can trace further back, the land snails prob- 

 ably to the Devonian, the Millipedes to the same period, and 

 the Scorpions and insects as far as the Silurian. No land ver- 

 tebrate is yet known, older than the Lower Carboniferous, but 

 there is nothing known to us in physical condition, to preclude 

 the existence of such creatures at least in the Devonian. 



It would take us too far afield to attempt to notice the in- 

 vertebrate land life of the Palaeozoic in general. This has been 

 done in great detail by Dr. Scudder. I shall here limit myself 

 to the animals found in our erect trees, and merely touch in- 

 cidentally on such others as may be connected with them. 



I have already mentioned the occurrence of a land snail, 

 a true pulmonate mollusk, in the first find by Lyell and my- 

 self at Coal Mine Point, and this was the first animal of this 

 kind known in any rocks older than the Purbeck formation of 

 England. It is one of the groups of so-called Chrysalis-shells, 

 scarcely distinguishable at first sight from some modern West 

 Indian species, and distinctly referable to the modern genus 

 Pupa. It was named Pupa vetusta, and a second and smaller 

 species subsequently found was named P. Bigsbyi, and a third 

 of different form, and resembling the modern snails, bears the 

 name Zonites priscus. The only other Palaeozoic land mol- 

 lusks known at present are a few species found in the coal 

 formation of Ohio, and a fragment supposed to indicate another 

 species from the Devonian plant beds of St. John's, New 

 Brunswick. .This last is the oldest known evidence of pulmon- 

 ate snails. If we ask the precise relations of these creatures to 

 modern snails, it may be answered that of the two leading sub- 



