Plate 36. 

 1-3. Colobocentrotus Mertensii Brandt. 



1. Seen from the aetinal side. 



2. The same seen from the abactinal side. 



3. The same specimen, seen in profile, facing the bivium and odd posterior interam- 



bulacrum. 

 All figures are natural size. 

 Bonin Ids., Captains Ringgold and Rodgers, N. P. Ex. Ex., Dr. Wm. Stimpson Coll. 



