IX 



PHYLUM ECHINODERMATA 



387 



there among the tubercles, usually one in the middle of each 



ossicle, are pedicellarics, which differ widely from those of Asterias. 



Each pedicellaria in An- 



thenea is a small, narrow, 



oblong, calcareous body, 



consisting of two parallel 



narrow valves or jaws : 



these, instead of being 



supported on a flexible 



stalk, are articulated with 



the edges of a slit-like 



depression on the surface 



of the flat ossicle, and are 



thus on a level with the 



general surface. The term 



valvulate is applied to 



pedicellarire of this de- 



scription. In a living 



Anthenea many of the 



pedicellariae will be found 



to have their valves widely 



open ; when they are 



touched the valves close 



together, gradually open- 



ing again after a little time. The ambulacral spines bounding 



the ambulacral grooves are flattened and blunt, and arranged 



in fan-like fasciculi. Round 

 the border separating the 

 aboral and oral surfaces 

 the plates are arranged 

 in two somewhat irregular 

 rows. 



The aboral surface is 

 strongly convex, but not 

 uniformly so, there being a 

 more or less distinct de- 

 pression in the form of a 

 shallow open groove, the 

 inter- radial depression, op- 

 posite each of the intervals 

 between the arms. The 

 surface is dotted over with 

 numerous small rounded 

 tubercles, arranged in some- 

 what irregular radiating 

 lines. These aboral tuber- 



FIG. 311. Anthenea, view of aboral surface. 



(After Sladen.) 



F,c, 3,2- 



, w )1)f oral Sl ,rfce. 



c c 2 



