FOREIGN DEVONIAN. 



297 



another, called Clymenia. Fig. 512, Goniatites retrorsus ; fig. 513, Clymenia 

 Sedgwickii. The shell in Clymenia has the form in the Ammonites, but, unlike 

 the Goniatites and Ammonites, the siphuncle is ventral instead of dorsal, and 

 the septa have no distinct dorsal lobe on the medial line, as shown in fig. 513 a. 



3. Articulates. — There are a number of species of Trilobites, though less 

 than in the Silurian : the genus P~hacops or Dalmania is most common. Homalo- 

 notus has European species, and one, H. armatus, has spines on the head and two 

 rows along the back. This spinous feature reaches its maximum in the Devonian 

 Arges armatus (fig. 514). 



Figs. 514, 515. 



Crustaceans.- 



-Fig. 514, Arges armatus ; 515, Slate containing [Cypridina serrato-striata, 

 natural size ; 515 a, same, enlarged. 



Minute Ostracoids, referred to the genus Cypridina, abound in the Cypridina 

 slate, giving this name to the beds. Fig. 515 represents a portion of the slate or 



Fig. 516. 



shale with the shells of the Cypridina s 

 and 515 a is one of the shells, enlarged 



Pterichthys Milleri. 



rato-striata on its surface, natural size, 



