236 



PALEOZOIC TIME — UPPER SILURIAN. 



trail of a sea-worm, or Annelid, reduced one-half. There were also 

 Orthocerata and Trilobites. 



Characteristic Species. -— *^_ 



1. Radiates.— (a.) Polyps.— Figs. 365, 366, Zaphrentis (Caninia) bilateralis; 

 367, Palseocyclus rotuloides, different views, from New York ; 368, a branching 

 Figs. 365-369. 



Radiates.— Figs. 365, 366, Zaphrentis bilateralis; 367, Palseocyclus rotuloides; 368, a, Cha>- 

 tetes; 369, a, Graptolithus Clintonensis. 



Chsetetes. (6.) Acalephs.— 369, a, Graptolithus Cliutonensis. (c.) Echinoderms : 

 Crinoids.—A few species are known : fragments are common, and they are often 

 found in the iron-ore as well as in the limestones. 

 Figs. 370-382. 



10a 



Mollusks.— Figs. 370, a, Fenestella ? prisca; 371, Pentamerus oblongus; 372, 373, part of 

 casts of the interior ; 374, 375, Atrypa reticularis ; 376, 377, Athyris (formerly Atrypa) 

 congesta; 378, Chonetes cornuta; 379, Avicula rhomboidea; 380, Cyclonema cancellata*, 

 381. track of a Bivalve ( X y A ) ; 382, track of an Annelid ? ( X Y 2 )• 



2. Mollusks. — (a.) Bryozoans.— Fig. 370, Fenestella f prisca. 



