402 AIR-BREATHERS IN THE COAL. [Cn. XXV 



gress in obtjiining a knowledge of the terrestrial fauna of tlie coal, since 

 the reptiles above enumerated seem to have been all amphibious. Nega- 

 tive evidence should have its due weight in paleontological reasonings 

 and speculations, but we are as yet quite unable to appreciate its value. 

 In the United States about five milhons of tons of native coal are annually 

 extracted from the coal-measures, yet no fossil insect has yet been met 

 with in the carboniferous rocks of North America. Ought we then to 

 conclude that at the period of the coal insects were unrepresented in the 

 forests of the Western World ? In like manner, no land-shell, no Helix, 

 Bulimus, Pupa, or Clausiha, nor any aquatic pulmoniferous moUusk, such 

 as Limneus or Planorbis, is recorded to have come from the coal of 

 Europe, worked for centuries before America was discovered, and now 

 quarried on so enormous a scale. Can w^e infer that land-shells were not 

 called into existence in European latitudes until after the carboniferous 

 peiiod ? 



The theory of progressive development w^ould account readily for the 

 absence of Chelonian and Saurian reptiles, or of Birds and Mammals, 

 from the Coal-Measures, because the condition of the planet is supposed 

 to have been too immature and unsettled to permit creatures enjoying a 

 higher development than batrachians to find a fit domicile therein. But 

 this same theory leaves the scarcity of the invertebrata, or the entire ab- 

 sence of many important classes of them, wdiolly unexplained. When 

 we generalize on this subject, we must not forget that the eighteen or 

 twenty individual insects and land-shells met with in the coal (and most 

 of these veiy recently found), are scarcely double the number of the car- 

 boniferous reptiles which have been established within the last ten years 

 on the evidence of bones and footjDrints. Yet our opportunities of ex- 

 amining strata formed in close connection with ancient land exceed in 

 this case all that we enjoy in regard to any other formations, whether 

 primary, secondary, or tertiary. We have ransacked hundreds of soils 

 replete with the fossil roots of trees, — have dug out hundreds of erect 

 trunks and stumps, which stood in the position in which they grew, — 

 have broken up myriads of cubic feet of fuel still retaining its vegetable 

 structure, — and, after all, we continue almost as much in the dark re- 

 specting the invertebrate air-breathers of this epoch, as if the Coal had 

 been thrown down in mid-ocean. The age of the planet, or its unpre- 

 pared state to serve as a dwelling-place for organized beings, cannot ex- 

 plain the enigma, because we know that while the land supported a lux- 

 uriant vegetation, the contemporaneous seas swarmed with life — with 

 Articulata, Mollusca, Radiata, and Fishes. We must, therefore, collect 

 more facts, if w^e expect to solve a problem, which, in the present state of 

 science, cannot but excite our wonder; and we must remember how 

 much the conditions of this problem have varied within the last ten 

 years. Meanwhile let us be content to impute the scantiness of our data 

 chiefly to our want of skill as collectors and interpreters, but partly also 

 to our ignorance of the laws which govern the fossilization of land- 

 animals, whether of high or low degree. 



