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 limestones of 

 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, Heliolites, and Cyatho- 

 phyllu??i, 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 polymorplia (fig. 554), one of the commonest of all 

 the Devonshire fossils. The Cyathophylhim cwspitosum (fig. 555) and 



Fig. 555. 



Fig. 554. 



Favosites polymorpha, Goldf. S. Devon, from a polished 



specimen. 



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



a. Cyathophyllwn cctspitosum, 



Goldf.. Plymouth. 



b. A terminal star. 



c. Vertical section, exhibiting 

 transverse plates, and part of 

 another branch. 



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

 very common species, the Aulopora serpens (fig. 557), which creeps over 

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



Fig. 557. 



Fig. 556. 



ffeliolites porosa, Goldf., sp. Porites pyriformis, 



Lonsi 

 a. Portion of the same magnified. Middle De- 

 vonian, Torquay ; Plymouth ; EifeL 



Aulopora serpens, Goldf. 



(The young basal portion of a Syringopora, 



Milne Edw. aud Haime.) 



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. 



