PALEOZOIC HOCKS AND 



289 



Radiates. Among corals, the characteristic Silurian 

 chain-corals (Halysitids) are gone, but the other two 

 forms remain, with different species (Figs. 200, 201). 

 The graptolites are gone, as also the Cystidean crinoids, 

 but the blastids or bud-crinoids are now far more abun- 

 dant, though they reach their maximum only in the 

 Carboniferous (Fig. 242, page 316). 



Bivalves and Univalves. Brachiopods still continue 

 in great numbers, of the characteristic Paleozoic, square- 

 shouldered forms (Fig. 202), and both Lamellibranchs 



FIG. 202. 



FIG. 203. FIG. 204. FIG. 205. 



FIGS. 202-205. Devonian brachiopods . 202. Spirifer perextensus. (After Meek.) 

 Devonian lamellibranchs and gasteropoda : 203. Ctenopistha antiqua. (After 

 Meek.) 204. Lucina Ohioensis. (After Meek.) 205. Orthonema Newberryi. 

 (After Meek.) 



and Gasteropods (univalves) are now more abundant. It 

 is well to note that fresh-water and land forms are now 

 for the first time introduced. 



Ceplialopods. The Orthoceratites still continue in 

 Devonian times, though in greatly diminished number 

 and size ; but we note here a great advance in the intro- 

 duction of a new form characteristic of this and the 

 Carboniferous, viz., the Ooniatites (angled stones), so 

 called because the suture or junction of the partition with 

 the shell is angled instead of simple (see Fig. 246, page 



LE CONTE, GEOL. 19 



