274 



PALAEOZOIC TIME DEVONIAN AGE. 







Fig. 452. 



(c. ) Echinoderms. — There are many species of Crinoids, and the large, 

 smooth stems of some of them are half an inch to an inch in diameter. 

 The species of most interest are the Nucleocrini (also 

 called Olivanites) ; they are representatives of the Pen- 

 tremite family, — a group which had its first species in 

 the Chazy, the early part of the Trenton period, in the 

 Lower Silurian, but which from that time appears to have 

 been extinct until the Corniferous period in the Devo- 

 nian. In the Subcarboniferous period it was very com- 

 mon. The species of this period are ovoidal, or like 

 an olive in shape, and have ambulacral areas closely 

 like those of the true (pentagonal) Pentremites (figs. 

 531, 532). Fig. 452 is the Nucleocrinus Verneuili. (The 

 name Nucleocrinus of Conrad antedates Oh'vanites of Troost, 

 as well as Elseacrinus of Roemer.) 



2. Molhisks — («.) Brachiopods. — Figs. 453 and 454, Spirifer acuminatum 

 Con. (S. cultrijuyatus Roemer), from New York and the West. Fig. 455, Spirifer 



Figs. 453-455. 



55 



Nucleocrinus Ver- 

 neuili. 



Brachiopods. — Figs. 453, 454, Spirifer acuminatus ; 455, Sp. gregarius. 



gregarius, very common in Indiana and Kentucky, at the Falls of the Ohio, and 

 at Middleton, Canada (Billings). Also, Pentamerus aratus, Chonetes hemisphe- 



Figs. 456, 457. 



Conchipers. — Fig. 456, Lucina? proavia; 457, Conocardium trigonale. 



rica, Atrypa reticularis, A. impressa, Strichlandia elongata (Billings), formerly 

 Pentamerus elongatus Vanuxem ; also a Galceola near C. sandalina (fig. 231), 



