$ S. CRUSTACEAN'S OF THE DEVONIAN SYSTEM. < oy 



Zoophytes. The Corals and Crinoidea are numerous. 

 and most of the genera, and many of the species, are 

 equally abundant in the Carboniferous system. The 

 * and Cyathophylla,\ are common both in the 

 mountain limestone and in the Devonian marbles. The 

 Crinoideans comprise several genera,, and some peculiar 

 species ithocrinus {ante, p. 600 ). and Peniremites 



(p. 650 . 



Jlollusca. The shells in some districts are very nume- 

 rous, consisting of many genera of gasteropoda: as. Buc- 

 einum, Turbo, Pleurotomaria, &c. : and conchifera.. as 

 Cucullcea, Avicula, Peeten, &c. 



But the most remarkable feature in the conchology of 

 this epoch is the abundance of the ancient types of braehio- 

 poda. In the British Devonian strata alone have been 

 determined of Atrypa. 20 species : Leptcena, 7 : Orth.is, 16 : 

 Spirifer, 34; Terebratula, 30. 



Cephalopoda. Of the higher order of molluscous ani- 

 mals, species of seven or eight genera are met with. The 

 most common belong to Belle ropli on. Orthoceras, Cyrto- 

 (jr natites, and Clymenia ; the latter differ from 

 the Goniatites in being fattened, and having an internal 

 siphuncle. and angular septa. J The Orthoceratites in the 

 limestones of Devonshire often attain a large size. The 

 shell is commonly changed into white calcareous spar, 

 which in sections, forms a beautiful contrast with the red 

 hue of the surrounding rock.§ 



8. Crustaceans of the Devonian - System. — In this 

 formation the palaeozoic types of Crustaceans, the Trilobites, 

 begin to appear in considerable numbers, and prepare us for 

 the myriads that are imbedded in the Silurian rocks. The 



* Medals of Creation, p. 2< ' + Ibid. p. 298. 



• ^re Mr. LyelTa Elements of Geology, p. 15?. fig. 342. 



§ Polished slices of marble marked with sec:: _- . jrthoceratites 

 are sold by the lapidaries of Torquay and Teignmouth. 



