140 THE IMPERFECTION OF 



it may possibly be said that no sponges are found for 

 such and such a period, because none existed in it. 

 The plausibility of such an opinion can only be tested in 

 fresh illustrations of the general argument. The coal- 

 field of Nova Scotia has been described by Professor 

 Dawson of Montreal. As it afforded a fine field for the 

 exertions of the geologist, so it repaid him by its great 

 richness in the fossil remains of plants. But in the 

 coal formations of England and of Westphalia insects 

 also had been found of different genera in addition to 

 plants, while Nova Scotia, with all its vegetable wealth, 

 yielded the anxious explorer but a single specimen of the 

 still more interesting relics. That specimen consisted 

 of the head and some other fragments of a large insect, 

 probably neuropterous. That single specimen Professor 

 Dawson tells us he found in a coprolite, in the fossil 

 excrement of a reptile enclosed in the trunk of an erect 

 sigillaria. Could any one invent a more curious cabinet 

 to preserve so fragile a specimen for millions of years ? 

 Can it in this case be argued, that of insect remains 

 nothing was found in the carboniferous of Nova Scotia 

 but the head and some other appurtenances of a single 

 neuropterous insect, because that head and those 

 appurtenances were all that had ever flourished there? 

 It cannot so be argued, not only because the analogies 

 of the carboniferous formation in other parts of the 

 world are conclusive against such argument, but also 

 because within the last three or four years, after long 

 and diligent search, two more species have been added 

 to the collection of carboniferous insects from Nova 



