258 



ASTEKOIDEA AND OPHIUROIDEA. 



Eucladia, described by Dr Henry Woodward from the Upper 

 Silurian, which apparently belongs to the section of the 

 Opliiuroids represented at the present day by Euryale, in 

 which the arms, instead of being simple, are bifurcated. 



Fig. 148. A, Outline of Eugaster Logani, of the natural size Devonian. B, Base of an 

 arm of the same viewed from below, enlarged, c, Outline of Protaster Forbesi, of the 

 natural size Upper Silurian. D, Base of arm of same, viewed from below, enlarged. E, 

 Portion of the arm of Ptilonaster princeps, viewed from below, enlarged Devonian : a, 

 Ambulacral plates ; 6, Adambulacral plates ; p, Pore. (After Hall.) 



As regards the Secondary and Tertiary Ophiuroids very 

 little need be said, partly because they approximate closely 

 to, or are identical with, recent generic types, or because they 

 are so imperfectly preserved, as a rule, that their determina- 



Fig. 149. Aspidura loricata. Muschelkalk. 



tion is exceptionally difficult. In the Trias appear the 

 genera Acroura and Aspidura (fig. 149), the latter being 



