458 ECHINIDAE. 



prominent than the others. In young specimens the uniformity in the size of 

 the tubercles of the interambulacral space is not so marked, the middle rows 

 on each side of the median line being the most prominent. 



Specimens of this species have undoubtedly been figured by Rumph as 

 Echinometra setosa, but have since his time been generally referred to Dia- 

 dema, Small specimens of this species with dark violet spines would readily 

 pass to a casual observer as the young of Diadema, .and although his original 

 specimens are no longer accessible, yet his figure is too characteristic of this 

 species, and too unlike any Diadema known, to pass for anything else. From 

 the geographical range of the specimens of this species in the Museum and 

 other collections, there is every probability that Rumph must have found 

 it in Amboina, as it ranges from Natal to the Sandwich Islands. 



Society [stands; Zanzibar; Natal. 



ECHINIDAE. 



Family Echinidae Agass, 1846, C. 11. Ann. Sc. Nat. VI. (emend.) 



This family is Dearly identical to the subdivision of Oligopores proposed 

 by Desor. It is here, however, circumscribed in such a manner as to include 

 the greater part of one of his subfamilies of Polyporidae, containing gen- 

 era like Hemipedina, Phymosoma, which it may yet be advisable to sepa- 

 rate into a subfamily when we know more respecting them from recent 

 species than we now know. The typical genus of this family is Echinus. 

 The mode of growth of the poriferous zone shows that the same type of 

 poriferous zone may form either a simple vertical zone with the pairs of 

 pores placed directly one above the other; or that one plate may be pushed 

 out laterally between the others, so that the poriferous zone becomes com- 

 posed of two vertical rows of pores ; or they may be pushed out laterally 

 to such an extent as to form three distinct vertical rows. Two of the sub- 

 divisions of this family proposed by Desor are here adopted, somewhat 

 modified. It is impossible, however, with the scanty material at our disposal 

 to characterize the subfamilies as distinctly, and to limit them as accurately, 



