SPONGES 42 1 



grew annually in thickness. The shape and arrangement of the 

 leaves differ much in the various genera; for example, they are 

 needle-like in Astrophyllites, while in Annularia they are broad 

 and at the base united into a ring around the stem. The shape, 

 size, and position of the spore-bearing organs likewise differ in the 

 different genera, but often resemble those of the modern horse- 

 tails. The base of the stem tapers abruptly, and is either con- 

 nected with a horizontal rhizome or gives off a bundle of roots. 

 Fragments of calamite stems are among the commonest fossils of 

 the coal measures (PL VI, Fig. 13). 



The Flowering Plants are still represented only by the Gym- 

 nosperms, of which Coi'daites is a common example. This plant 

 had a slender trunk, branching above into a pyramidal shape and 

 having long, broad, pointed leaves like those of certain lilies in 

 form. The trunk had a large, soft, inner pith. Cordaites is 

 referred to the Cycad division of the Gymnosperms, but has 

 certain resemblances to the Conifers, which were probably also 

 present in the Carboniferous vegetation. 



The Carboniferous flora is merely the Devonian flora some- 

 what advanced and diversified, but the forests were of the same 

 gloomy, monotonous character as before. The wide distribution 

 and uniform character of this flora are very remarkable ; we find 

 the same or nearly allied species of plants spread over North 

 America, Europe (even in the polar lands, like Spitzbergen and 

 Nova Zembla), Siberia, China, the Sinai peninsula, Brazil, Aus- 

 tralia, and Tasmania. This uniformity of vegetation indicates a 

 corresponding similarity of climate over nearly the whole world, 

 for no trace of climatic zones can be found. 



Foraminifera. — For the first time these animals assume con- 

 siderable importance in the earth's economy. Many genera which 

 are still living had representatives in the Carboniferous seas, but 

 the most conspicuous and abundant is the extinct Fusulina (PI. VI, 

 Fig. 1), a very large kind, with shells resembling grains of wheat 

 in size and shape. This genus is especially developed in the 

 Upper Carboniferous. 



Sponges are common, though rarely found in good preservation. 



