Plate 41. 

 1-7. ColobocentrotUB Stimpsoni A. Ag. 



1. The left anterior interambulacrum. 



2. The ninth and tenth plates from the actinal system of the left anterior interambu- 



lacrum. 



3. Showing the large tubercle of the fifth plate from the actinal system, at the ambitus of 



the left posterior interambulacrum. 



4. The same, seen in profile. 



5. One of the primary interambulaeral tubercles on the abactinal side. 



6. Grouping of the miliaries on the actinal side of the right posterior interambulacrum. 



7. Genital plate and pore of the left anterior interambulacrum. 



All the figures are from the same specimen, measuring 88 mm. in diameter, including the 

 spines. 



lionin Ids., Captains Ringgold and Rodgers, N. P. Ex. Ex., Dr. Wm. Stimpsou Coll. 



