ABATUS CAVEBNOSUS. 



213 



There are five spheridia near the actinostome, one in each ambulacral 

 area (PI. 99, fig. 1). 



Each interambnlacrum has one actinal plate followed by four and a half 

 coronal plates carrying on each plate from one to six primary and secondary 

 tubercles. The ambulacral areas are bare. In older specimens l 3 mm. in 

 length there is a miliary in each ambulacral plate. 



5 ' 



1.6 mm. 



FlG. 307. A. CAVERNOSUS. 



5 

 1.9 mm. 



Flu. o08. A. CAVEBNOSUS. 



Loven is right in objecting to the association of Abatits cavernosus Trosch. 

 with Hemiaster.- The structure of the abactinal system of Hemiaster is 



abb 

 37 mm. 



Fig. 309. A. cavernosus. Fig. 310. Hemiaster bufo. 



After Loven. 



S 

 37 mm. 



Fig. 811. Abatis cavernosus. 



of an ancient t} r pe, Fig. 310, while that of Abatus is eminently Schizas- 

 teroid. Fig. 311 (PI. 99, fig. 9), but neither Troschel nor myself had noticed 

 the difference in the structure of the abactinal system of Abatus and Hemi- 

 aster first detected by Loven. 



1 "Challenger " Echinoidea PI. XX a , figs. 9, 10. 2 Pourtalesia, p. 72. 



