I/O HISTORICAL PALEONTOLOGY. 



the "under clay," which forms the floor of a bed of coal, and 

 which represents the ancient soil upon which the SigiHaHtegr&vr. 

 The Lepidodendroids and Sigillarioids, though the first were 

 certainly, and the second possibly, Cryptogamic or flowerless 

 plants, must have constituted the main mass of the forests of 

 the Coal period; but we are not .without evidence of the exist- 

 ence at the same time of genuine " trees," in the technical 

 sense of this term namely, flowering plants with large woody 

 steins. So far as is certainly known, all the true trees of the 

 Carboniferous formation were Conifers, allied to the existing 

 Pines and Firs. They are recognised by the great size and 

 concentric woody rings of their prostrate, rarely erect trunks, 

 and by the presence of disc-bearing fibres in their wood, as 

 demonstrated by the microscope; and the principal genera 

 which have been recognised are Dadoxylon, Palczoxylon, 

 Araucarioxylon, and Pittites. Their fruit is not known with 

 absolute certainty, unless it be represented, as often conjectured, 

 by Trigonocarpon (fig. 113). The fruits known under this 

 name are nut-like, often of consider- 

 able size, and commonly three- or six- 

 angled. They probably originally pos- 

 sessed a fleshy envelope; and if truly 

 referable to the Conifers, they would 

 indicate that these ancient evergreens 

 produced berries instead of cones, 

 and thus resembled the modern Yews 

 rather than the Pines. It seems, 

 further, that the great group of the 

 Cycads, which are nearly allied to the Conifers, and which 

 attained such a striking prominence in the Secondary period, 

 probably commenced its existence during the Coal period ; 

 but these anticipatory forms are comparatively few in number, 

 and for the most part of somewhat dubious affinities. 



CHAPTER XIII. 



THE CARBONIFEROUS PERIOD Continued. 

 ANIMAL LIFE OF THE CARBONIFEROUS. 



We have seen that there exists a great difference as to the 

 mode of origin of the Carboniferous sediments, some being 

 purely marine, whilst others are terrestrial; and others, again, 



