306 



PALAEOZOIC SYSTEM OF ROCKS. 



columnar masses (Rugosa). Their upper portions are cup-shaped, and 

 the radiating lamince are very 

 distinct. In Favositids (Fig. 

 307) the hexagonal parallel col- 

 umns are divided somewhat 

 minutely by horizontal plates 



Fig. 304. 



Fig. 306. 



Figs. 304-306.— Cyathophylloid Corals: 304. Lonsdaleia floriformis (after Nicholson). 305. a 

 and b. Zaphrentis bilateralis (after Hall). 306. Strombodes pentagonus (after Hall). 



Fig. 307. 



Figs. 307-309.— Fa vositid and Halysitid Corals: 307. Columnaria alveolate: a, vertical; b. cross- 

 section (after Hall). 308. Syringopora verticillata. 309. Halysites catenulata (after Hall). 



