240 



PALAEOZOIC TIME UPPER SILURIAN. 



in figs. 389-391; Brachiopods, in figs. 392-404; Conchifers and 

 G-asteropods, in figs. 405-407 ; Trilobites, in figs. 408-411. Penta- 

 merus oblongus of the Clinton epoch (fig. 371) is abundant in the 

 Niagara limestone of Wisconsin and Iowa. 



Characteristic Species. 



1. Radiates. — (a.) Polyps (Corals). — Fig. 383, Chonoplxyllum Niagarense 

 (Conophyllum of Hall, a genus first published in 1852, two years after Chono- 

 phylluin by Edwards) ; 384, Favosites Niagarensis ; 384 a, surface of same, 

 enlarged, showing outline of cells; 385, Halysites catenulata ; 386, Heliolites 

 spinipora H.; 387, an enlarged view, showing the 12-rayed cells and the inter- 

 val of a cellular character separating them, both of which are distinguishing 

 characteristics of the genus Heliolites ; 388, Stromatopora concentrica. 



(b.) Echinoderms. — Fig. 389, Ichthyocrinus Isevis Conrad, a species which is 

 sometimes twice as large as the figure; 390, Caryocrinus ornatus Say, of Lock- 

 port, the nut-like shape having suggested the generic name (from Carya, the 

 hickory-nut); 391, Stephanocrinus angulatus Conrad, of Lockport; or, part of 

 the stem, enlarged; b, joint of the stem, top-view : c, base of the body, showing 

 the three pieces of which it consists. Also, fig. 156 (page 148), the Cystid 

 Callocystites Jewettii H., and fig. 154, the Star-fish Palseaster Niagarensis. 



Figs. 389-391. 



Crinoids.— Fig. 





), Ichthyocrinus lsevis; 390, Caryocrinus ornatus; 391, a, b, c, Stephano- 

 crinus angulatus. 



2. Mollusks. — (a.) Bryozoans. — Many species of delicate corals of the 

 genus Fenestella, resembling fig. 370, and of other genera, (b.) Brachiopods. — 

 Fig. 392, Strophomena rugosa ; 393, Lejjtsena transversalis Dalman; 394, Atrypa 

 nodostriata, the Niagara form of this species; 395, same, side-view; 396, Me- 

 rista nitida ; 397, Pentamerus interplicatus ; 398, a, Rhynchonella cuneata ; 399 a, b, 

 Leptocozlia disparilis ; 400, Orthis bilobus ; 400 a, same, enlarged; 401, Sjnrifer 

 Niagarensis; 402, same, side-view; 403, 404, Sp. suleatus. Among these, all but 

 the Leptocoelia disparilis, Atrypa nodostriata, and the Orthis and Spirifers, are 

 found also in European rocks. 



