538 



MIDDLE DEVONIAN. 



[Ch. XXVI. 



species), both in England and on the Continent. In Germany they 

 are usually confined to distinct beds, as at Oberscheld, also at Couvin 

 in Belgium, &c. Trilobites are not unfrequent in Cornwall ; they are 

 chiefly restricted to species of Phacops,. P. Icevis, &c, but in the upper 

 Devonian limestones of the Fichtelgebirge, as at Elbersreuth in Bava- 

 ria, there are numerous other genera and species, such as Brontes, 

 Cyphastis, &c, which never rise higher in the series or appear in any 

 portion of the carboniferous limestone. 



Middle Devonian. 



The unfossiliferous series (No. 2, p. 536) of North Devon, and the 

 calcareous beds of Ilfracombe (3), correspond to the Dartmouth and 

 Plymouth 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 Favo- 

 sites, Heliolites and Cyathophyllum, the last genus equally abundant 

 in the Silurian and Carboniferous 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 polymorphs 

 (fig. 605), one of the commonest of all the Devonshire fossils. The 

 Cyathophyllum ccespitosum (fig. 606) and Heliolites pyriformis (fig. 



Fm. 605. 



Fig. 605. 



Favosites polymorpha, Goldf. S. Devon, from 



a polished specimen. 



a. Portion of the same magnified, to show the 



pores. 



a. Cyathophyllum ccespitosum, G old£ 

 Plymouth and Ilfracombe. 



&. A terminal star. 



c. Vertical section, exhibiting trans- 

 verse plates, and part of another 

 branch. 



60*7) are peculiarly characteristic ; as is another very common species, 

 the Aulopora serpens (fig. 608), which creeps over corals and shells in 

 its young state, as here figured, but afterwards grows upwards and 



