PALEOZOIC TIME — LOWER, SILURIAN. 



511 



clustered steins, Fig. 706, with the cells above stellate. A species of Tetra- 

 dium, T. Jibratum of Tennessee, is represented, in Fig. 707. 



Minutely columnar Bryozoan corals of the Monticulipora tribe were 

 very numerous, 70 or 75 species having been described from the Cincinnati 

 beds. 



704-708. 



705t 



!m 



MS:.M 







»> ^Tvrv o^::*. r>r:. ^xrT^n^ r 



l"?^.©i 



crfe?-- 



m 



Fig. 704, Favistella stellata ; 705, Halysites gracilis ; 706, Sarcinula (?) obsoleta ; 707, a, Tetradium flbratum ; 



708, Gl3'ptocrinus decadactylus. Hall. 



The Echinoderms included Crinoids and Cystoids of several kinds. Fig. 

 708 represents a fine Glyptocrinus, one of the most common ; and Fig. 703, a 

 remarkable Star-fish from the Cincinnati beds, Palceaster Jamesi D. Two 

 other ficne Star-fishes from the same locality (P. Dyeri Meek and P. magnificus 



709-712. 



Lamellibkanchs. — Fig. 709, Avicula demissa ; 710, Ambonychia radiata ; 711, Modiolopsis modiolaris (x |) ; 



712, Ortbodesma parallelum. Hall. 



713. 



Miller) have a diameter of about six inches. Bryozoan corals also are com- 

 mon in the Cincinnati beds. 



The Brachiopods are nearly the same as in the Trenton. 



Lamellibranchs are rather common, they being usually 

 more abundant in shales and shaly sandstones than in lime- 

 stones. Some of the kinds are shown in Figs. 709-712. 



Of the Gastropods represented on page 507, Figs. 673-675 

 are also Hudson group species ; and the same is true of the 

 Lituites ( Trocholites) Ammonius, Fig. 688. Of Cephalopods, the Cincinnati 

 beds have afforded 13 species of Orthoceras, 5 of Endoceras, 4 of Lituites, 

 and 10 of other genera. 



Head-shield of Triar- 

 thrus Beekii. 



