THE ECHTNODERMATA 



251 



feature in many inadunates. Herpetocrinus (Sil.) is found 

 with the stem spirally coiled, concealing the crown, but 

 it could straighten itself when such protection was not 

 necessary. 



Platycrinus (Fig. 71, b, Carb.) is a monocyclic, transi- 



FlG. 70,-^-CRINOID COLUMNALS. 



#. b, e, f, g, Views of articular surfaces ; c, vertical section of part of stem ; 

 d, internal cast in place in rock-matrix ; e', side view. The thick black 

 in a-d represents cavities. (All about natural size.) (After Goldfuss.) 

 <z, Actinocrinus granulatus Goldfuss, Devonian, b, Cyathocrinus 

 rugosus Milkr, Devonian, c, d, Cyathocrinus pinnatus Goldfuss, 

 Devonian, e, e', Encrinus moniliformis Miller, Triassic. f t lsocrinus 

 basaltiformis (Miller), Jurassic, g, Bourgueticrinus ellipticus (Miller), 

 Upper Cretaceous (Upper Chalk). Dotted line = long axis of articular 

 surface below. 



tional from Inadunata to Camerata. The basals are re- 

 duced to three by fusion ; the symmetry is almost perfect, 

 there being only a slight difference between the anal 

 interray and the others ; the arms branch repeatedly, and 

 have a large crescentic articulation on the radials. The 



