'296 



PALEOZOIC TIME DEVONIAN AGE. 



that the clumsy Orthocerata of the Silurian age were succeeded by 

 fewer and smaller species. 



Just before the Devonian age closed, there were Reptiles in the 

 world. This is a second step in the unfolding of the Vertebrate 

 type. The skeleton of one small species, called Telerpeton, is repre- 

 sented in fig. 520. Moreover, besides these remains, tracks of 

 Amphibians have been observed, proving that air-breathing animals 

 frequented the marshes. 



Characteristic Species. 



1. Radiates. — Among Radiates there were species of Pentremites, the earliest 

 in Europe of the group of Blastoid Crinoids. 



2. Mollusks. — Brachiopods included species of Orthis, Strophomena, Atrypa, 

 Rhynchonella, Spirifer, Productus, Chonetes, etc.; besides Calceola and Stringo- 

 cephalus, which are confined to the Devonian age. Fig. 231 is the Calceola san- 

 dalina (so called from the sandal-like shape of the shell). This genus characterizes 

 the Calceola schist which underlies the great Devonian limestone of the Eifel. 



Conchifers were numerous of the genera Avicida, Aviculopecten, Pterinea, Nu- 

 cula, Conocardium ; also of Area, Grammysia, Megalodon, etc. There were 

 Gasteropods (all without beaks) of the old genera 3furchisom'a, Euomphalus, 

 Pleurotomaria, Loxonema, Bellerophon, etc. There were others also of the new 

 genus Porcellia, which is near Bellerophon, and somewhat resembles an Am- 

 monite in form, but has a deep dorsal slit in the aperture of the shell. 



Figs. 512, 513. 



Cephalopods.— Fig. 512, Goniatites retrorsus ; 513, Clymenia Sedgwickii; 513 a, dorsal view 



of septa. 



Cephalopods include a few species of the Orthoceras family, — also Nautili, and 

 several species of the new genus Goniatites, of the Ammonite family, and of 



