332 



PALAEOZOIC SYSTEM OF ROCKS. 



the coal-measures, therefore, are here found, though imperfectly devel- 

 oped, and the coal not workable. The Carboniferous day is already 

 dawning. 



Animals. 



In accordance with our prescribed plan, all we can do in describing 

 Devonian animals is to touch prominent points — to notice what is going 

 )out, what is coming in, some few characteristic forms, and to dwell 

 only on what bears on evolution. 



Radiates. — Among corals, the chain-corals (Halysitids) have disap- 

 peared ; the other orders continue under different species (Figs. 403- 

 406). Among Hydrozoa, the Graptolites are gone ; among Crinoids, 

 the Cystids are gone, but in their place the Blastoids (bud-like), those 

 curious armless crinoids, with petalloid markings already spoken of as 

 rare in the Silurian, become more abundant. The Crinids, or plumose- 

 armed crinoids, continue undiminished. The Blastoids, however, are 

 still more characteristic of the Carboniferous. We therefore defer their 

 illustration to that period. 



Brachiopods. — Brachiopods are still very abundant, and still many 

 of them of the characteristic Palaeozoic, square-shouldered type. Among 



Fig. 409. FlG - 41 °- 



Figs. 407-410.-Devonian Brachiopods: 407. Spirifer ' fornacnia (after ■Meek .and Worthen): a. 

 Ventral valve; b. Suture. 408. Spirifer perextensus (after Meek). 409. Orthis Livia. a, Don>al, 

 b, Side view. 410. Strophomena rhomboidalis. 



spirifers, the long-winged species (Fig. 409) are very abundant and 

 characteristic. We give a few figures of Devonian bivalves, both 



