426 PROF. F. J. BELL ON THE ECHINOMETRID.S;. [Mar. 1.5, 

 StRONGYLOCENTROTUS ARMIGER. 



StRONGYLOCENTROTUS BULLATUS. 



StRONGYLOCENTROTUS DEPRESSUS. 



A dry test, denuded of spines, is very probably to be referred to 

 this species ; I proceed, however, to point out a number of cha- 

 racters by which it appears to diifer from the descriptions of »S. de- 

 pressus as given by Prof. Alex. Agassiz, or the E. disjunctus of Prof. 



Fig. 1. 



Ambulacra! area of S. depressus, to show the disposition of the pairs of pores. 



von Martens. The test is not so depressed ; the primary tubercles 

 are not so numerous ; the poriferous zone is not specially broad ; and 

 it is not the uppermost, but the lowermost pair of pores that is "dis- 

 junctum." As to this last point, however, there is possibly some 

 error of observation, as it is difficult to see the exact position of the 

 pair of pores in question, since they lie altogether at the edge of the 

 plate. If the difference is real, it is probably one of specific impor- 

 tance. Prof. Agassiz remarks that in specimens with a depressed 

 test, "the inner and one outer pairs of pores " are disconnected. 



