THE CARBONIFEROUS PERIODS 



481 



f w " a C 



Fig. 452. — Mississippian echinoderms. Crinoids : A, Actinocrinus multiradiatus ; 

 By Platycrinus discoideus ; C, Onychocrinus exsculptus ; D, Batocrinus (Dizygocrinus) 

 rotundus (with arms removed) ; E, the same as D with arms. Blastoids : F, Pentre- 

 mites robustus ; G, Pentremites pyriformis. Brittle Stars : H, Ony chaster flexilis. 



medes (Fig. 453). The Carboniferous was rich in brachiopods (Fig. 

 454 A-M), but before its close the leading Paleozoic genera had dis- 

 appeared. One characteristic genus (Productus) ^j^ 

 (Fig. 454 A, G) had one large, convex, spinose 

 valve and one concave one. 



Mollusks. — Gastropods (Fig. 455 A-G) and 

 pelecypods (Fig. 456 A-F) continued much as in 

 the Devonian. The cephalopods (Fig. 457 A-E), 

 on the other hand, showed considerable advance 

 in the complexity of the suture lines (p. 530). The 

 angle-sutured goniatites were common, and, be- 

 fore the close of the Permian, ammonites with 

 their complex sutures appeared. Some of the 

 straight, simple orthoceratites continued through- 

 out the Paleozoic into the Triassic. 



Arthropods. — Trilobites (Fig. 458) and euryp- 

 terids continued into the Carboniferous, but be- 

 came extinct at its close. 



Insects. — The earliest insects of which any 

 fossils have as yet been found lived in the Car- 

 boniferous (Fig. 459 A, B), and from that period , ^jo. 453- — Car- 

 1 • 1 1 1 *i 1 *t>i bomferous brvozoan : 



about 1000 species have been described. They Archimedes wortheni 



appear to have been more generalized than those (Mississippian). 



