THE ECHINODERMATA 249 



Chalk. It is one of the few crinoids that were not fixed 

 in the adult stage. By analogy with the modern free 

 crinoid Antedon we may infer that it was stalked in a 

 larval stage, but of this there is no actual evidence. The 

 top columnal, however, is apparently retained as a large 

 pentagonal plate in the centre of the dorsal cup. Around 

 and above this are five large pentagonal infrabasals, then 



A.F. 



A.F. 



A.F: 



C.D. 

 FIG. 69. MARSUPITES TESTUDINARIUS (SCHLOTHEIM), CAMPANIAN 



(UPPER CHALK). 

 (Cup without arms, natural size.) (Original.) 



A.F., Arm-facets; B, basal plates; C.D., centro-dorsal plate ; IB, infra- 

 basals ; R, radials. 



five large hexagonal basals, and five large pentagonal 

 radials, with facets for the arms. So far as the dorsal 

 cup goes there is perfect five-rayed symmetry, and the 

 dicyclic condition is shown very simply and clearly. 



The arms branch repeatedly. The ventral surface is 

 never preserved, but we may assume that, as in other 

 post-Palaeozoic crinoids, it consisted of many small 

 plates forming a flexible surface, on which lay open food- 



