THE CARBONIFEROUS PERIOD. 



187 



are highly characteristic, as are the slender toothed branches 

 of Glauconome (fig. 126, fr). A more singular form, however, is 

 the curious Archimedes (fig. 126, c}, which is so characteristic 

 of the Carboniferous formation of North America. In this re- 

 markable type, the colony consists of a succession of funnel- 



rig. 126. Carboniferous Polyzoa. a, Fragment of Polypora dcndroidea, of the 

 natural size, Ireland ; ' Small portion of the same, enlarged to show the cells ; 6, 

 Qlauconome pulcherrima, a fragment, of the natural size, Ireland ; 6', Portion of the 

 same, enlarged ; c. The central screw-like axis of Archimedes Worthenl. of the natural 

 size Carboniferous, America ; c', Portion of the exterior of the frond of the same, 

 enlarged ; c". Portion of the interior of the frond of the same showing the mouths of 

 the cells, enlarged. (After M'Coy and Hall. ) 



shaped fronds, essentially similar to Fenestella in their structure, 

 springing in a continuous spiral from a strong screw-like vertical 

 axis. The outside of the fronds is simply striated; but the 

 branches exhibit on the interior the mouths of the little cells 



