PALEOZOIC TIME — UPPER SILURIAN. 



54T 



A few of the many Corals in the Niagara group are represented in 

 the following figures, 761-766. Fig. 761 is one of the Cyathophylloids or 

 cup Corals ; 762, a Favosites, a columnar, tabulate Coral, so named from favus, 

 a honeycomb, in allusion to its columnar structure ; 763, a chain Coral, or 



761-766. 



COKALS. — Fig. 761, Chonophyllum Niagarense ; 762, a, Favosites Niagarensis ; 763, Halysites catenulatus ; 764, 

 765, Heliolites spiniporus ; 766, Stromatopora concentrica. Hall. 



species of Halysites, mostly imbedded in the limestones ; 766, a Stromatopora, 

 a calcareous Hydroid, the lines showing the edges of the very thin, barely 

 distinguishable layers. 



Figs. 767-770 are the forms of some of the common Crinoids and Cystoids. 

 In Fig. 767 the arms clustered about the mouth of the Crinoid are perfect. 

 Fig. 768 has the box-like body of a Cystoid, to which group it is related. It 



767-770. 



CElKorDS. — Fig-. 767, Ichthyocrinus kevis ; 768, Caryocrinus ornatus ; 769, a, b, c, Stephanocrinus angulatus ; 



770, Troostocrinus subcylindricus. Hall. 



had slender arms, three to four inches long, fixed to the top of the box, 

 which were very fragile and are seldom preserved. The stem is sometimes 

 found six to eight inches long. The genus Stej^hanocrinus, Fig. 769, includes 

 Crinoids with short delicate arms. Among Cystoids, Callocystites Jewetti, 

 Fig. 444, page 429, is very common. 



Besides the above forms, the Niagara group has afforded the first of the 



