SUBCARBONIFEROUS PERIOD. 



313 



enlarged ; fig. 534 a, a plate of the same species, enlarged about two dia- 

 meters; fig. 535, a plate of Archseocidaris Noriooodi H., natural size, from 



Fig. 536. 



Palseechinus (Melonites) mnltipora (X/^)- 



Outline view of the restored 

 Melonites. 



Fig. 537 



the Kaskaskia limestone,- fig. 536, Melonites mnltipora, from the St. Louis 

 limestone, half natural size, but crushed; 536 a, an outline, showing the 

 form of the unbroken shell. The genus Archseo- 

 cidaris, like the modern Cidaris, has large promi- 

 nences on the plates to support the spines, which 

 are also large. In Melonites and Palseechinus the 

 plates are without prominences, and the spines 

 were small. The Pentremites above mentioned occur 

 through nearly all the limestone or upper group in 

 Tennessee. 



3. Mollusks. — (a.) Bryozoans.—Fig. 537 a, 

 Archimedes reversa, being a portion of the spiral 

 axis with the reticulated expansion removed. Fig. 

 537 b, a portion of the reticulated expansion of A. 

 Wortheni, magnified and showing the non-poriferous 

 surface. Fig. 537 c, the poriferous side of the same. 



(b.) Brachiopods. — Fig. 538, Chonetes ornata 

 Shumard (nat. size), from the Lithographic and Fig. 537 a Archimedes reversa • 

 Chouteau limestones, Missouri ; 538 a, enlarged sur- 537 b, c, A. Wortheni. 



