Plate 89. 

 Sperosoma obscurum A. Ag. and CL. 



1. Actinostome and base of corona, x 2. 



2. Abactinal system, x 2. 



3. Actinal ambulacral and interambulacral plates, just below ambitus, x 1.3. 



4. Abactinal ambulacral and interambulacral plates, just above ambitus, x 1.2. 



