74 VESTIGES OF THE 



of tlic ganoid fishes, are considered as at their apogee, or 

 point of greatest abundance ; a fact of some importance, 

 seeing that they partake of the hzard character, a genus 

 of a higher oixler of animals wliich we are soon to see 

 entering upon the stage. Of this hnk family is the 

 Megalichthys Hibbertii, found by Dr. Hibbert Ware, in 

 a limestone bed of fresh-water origin, underneath the 

 coal at Burdiehouse, near Edinburgh. Others of the 

 same kind have been found in the coal measures in York- 

 shire, and in the low coal shales at Manchester. The 

 chief other fishes of the coal era are named palaeothrissum, 

 paLngoniscus, diperdus. 



Coal strata are nearly confined to the group termed 

 the carboniferous formation. Thin beds are not un- 

 known afterwards, but they occur only as a rare excep- 

 tion. It is therefore thought that the most important 

 of the conditions which allowed of so abundant a terres- 

 trial vegetation had ceased about the time when this 

 formation was closed. The high temperature was not 

 one of the conditions which terminated, for there are 

 evidences of it afterwards ; but probably the super- 

 abundance of carbonic acid gas supposed to have existed 

 during this era was expended before its close. There can 

 be little doubt that the infusion of a large dose of this 

 gas into the atmosphere at the present day would be 

 attended by precisely the same circumstances as in the 

 time of the carboniferous formation. Land animal life 

 would not have a place on earth ; vegetation would be 

 enormous; and coal strata would be formed from the 

 vast accumulations of woody matter, wdiich Avould gather 

 in every sen., near the mouths of great rivei's. On the 

 exhaustion of the superabundance of carbonic acid gas, 

 the coal formation would cease, and the earth might 



