SILURIAN FOSSILS 



59 



Coenites (called Cladopora in older publications) grows in branch- 

 ing colonies (fig. 82) made up of parallel masses of tubes radiating 

 from the center of the branches or covering both sides of a leaf-like 

 colony. Several species are found in our Silurian. 



Arachnophyllum (called Strombodes in older publications) grows 

 in hemispherical colonies and has large, polygonal tubes (fig. 83). A_. 

 striatum is common in the Niaaiaran. 



Fig. 81 



Favosites (fig. 84) is the honeycomb coral (its name is de- 

 rived from the Latin for honeycomb and of all the colonial corals, 

 it is t"he one that looks most like a honeycomb). The walls of the 

 cups are thin (they are thick in Thecia) . The genus is represented 

 by 6 common species. 



Thecia minor is somewhat like Favosites but the walls of the 

 cup are thick; it is common in the Upper Niagaran. 



Fletcheria ( Pycnostylus in older publications) is a colonial 

 coral like Favosites and Thecia , but unlike these two it has cups, 

 better tubes (fig. 85), that are not closely crowded together; the 

 cups are without crossbars, unlike Syringopora , but they bud from 

 each other at intervals. The floor-like diaphragms across the 

 tubes are characteristic. Two common species are abundant in 

 the Upper Niagaran. 



Syringopora (fig. 86) suggests amass of spaghetti with cross- 

 bars joining the tubes at right angles. The crossbars may be con- 

 fused with the budding points in Fletcheria at first, but they are 

 numerous and never continue upward to form a new cup; also, they 

 are always at right angles to the tubes whereas the budding indivi- 

 duals in Fletcheria are at an acute angle to the parent tube. Two 

 species of Syringopora are common in the Springfield and Cedar- 

 ville. 



Heliolites (fig. 87) is massive like Favosites but it has a distinc- 

 tive appearance because the cups are round and do not touch each other. 

 They are separated from each other by smaller, polygonal tubes. We 

 have 3 common species. 



Lyellia is like Favosites but has round cups set close together and 

 without smaller polygonal tubes between them. One species is common 

 in the Dayton. 



The remainder of our common corals are solitary or "horn" cor- 

 als. Cystiphyllum (see fig. 161) is distinguished 

 from all the others because of the blister -like 

 growths which mask the septa in the cup. C_. nia- 

 garense is common in the Niagaran. 



The remaining horn corals all have dis- 

 tinct septa. Amplexus is unique in that none of 

 the septa reaches the center of the cups; they do 

 so in all the remaining species. A species of 

 Amplexus is common in the Upper Niagaran. 



Heliophyllum (see fig. 162) grows quite large; its 

 septa have wavy edges, as in the next genus, and they 

 are slightly twisted at the center of the cup. A species 

 of Heliophyllum is common in the Upper Niagaran. 



Zaphrentis (fig. 88) is very similar to Heliophyl- 

 lum but has straight septa, not twisted at the center of 



Fig. 82 



Ik 



Fig. 83 -pp- 



Fig. 84 



VrPm 



Fig. 87 



