Plate 72. 

 Arseosoma bicolor A. Ag. and CI. 



1. Actinostome and base of corona, x 1.7. 



2. Abactinal system. X 2.3. 



3. Actinal ambulacral and interambulacral plates, seven millimeters from ambitus. X 1.8. 



4. Abactinal ambulacral and interambulacral plates, eight millimeters from ambitus. X 2. 



