422 



FOSSILS OF THE 



[Ch. XXVI 



groups of Prof. Sedgwick's South Devon series, and are the most typical 

 portion of the Devonian system. They include the great hmestones oi 

 Plymouth and Torbay, replete with shells, trilobites, and corals. A thick 

 accumulation of slate and schist, full of the same fossils, occupies nearly 

 all the southern portion of Devonshire and a large part of Cornwall. 

 Among the corals we find the genera Favosites^ Helioliies, and CyatJio- 

 fhyllum^ the last genus equally abundant in the Silurian and Carbonifer- 

 ous systems, the two former so frequent in Silurian rocks. Some few 

 even of the species are common to the Devonian and Silurian groups, as, 

 for example, Favosites polymorpha (fig. 554), one of the commonest of all 

 the Devonshire fossils. The Cyathopliylluni ccespitosum ^fig. 555) and 



Fig. 555. 



Fig. 554. 



Favosites polymorpha, Goldf. S. Devon, n-om a polished 

 specimen. 



a. Portion of the same magnified, to show the pores. 



a. Oyathaphyllum ccenpitosum^ 



Goldf., Plymouth. 

 5. A terminal star. 

 c. Vertical section, exhibiting 



transverse plates, and part of 



anotLier branch. 



Heliolites pyriformis (fig. 556) are peculiarly characteristic ; as is another 

 very common species, the Aulo2:>ora serpens (fig. 557), which creeps over 

 corals and shells in its young state, as here figured, but afterwards grows 



Fig. 551. 



Fig. 556, 



BeUolites porosa, Goldf., sp. Porites pyriformis. Aulopora serpens, Goldf. 



L*^"^*^- (The young basal portion of a Syringopora^ 

 a. Portion of the same magnified. Middle De- Milne Edw. and Haime.) 



vonian, Torquay ; Plymouth ; Eifel. 



upwards and becomes a cluster of tubes connected by minute processes, 

 In this state it has been supposed to be a distinct coral, and has been 

 called Syringopora. 



