TOXOPNEUSTES PILEOLUS. 497 



size of the actinal cuts and of the projecting lips of the interambulacral part 

 of the cuts. This species is figured by Valenciennes in the Atlas du Voyage 

 de la Venus, but the lips are somewhat exaggerated and are not so promi- 

 nent in the original. 



Christmas Island ; Bourbon. 



Toxopneustes pileolus 



! Echinus pileolus Lam., 1816, An. s. Vert. 



! Toxopneustes pileolus Agass., 1841, Monog. Scut. Int. 



PI. V IIP. f. 1-2; PL XXV. f. 20, 21 ; PI. XXXVIII. f. w, n. 



The differences formerly considered as specific between the species of this 

 genus do not hold when a large series of specimens is examined. The vari- 

 ations found in specimens from different localities and of various sizes are 

 very considerable, extending to the breadth of the poriferous zone, the size 

 of the pores, the proportions of the actinostome, the concavity of the actinal 

 surface, and the greater or less conical outline of the test. 



In young specimens of Toxopneustes the arrangement of the pores is in arcs 

 of three pairs ; the actinostome is not sunken ; the cuts are slight ; the sec- 

 ondary and primary tubercles are arranged somewhat irregularly upon the 

 plates both of the ambulacral and interambulacral regions, forming only 

 two regular vertical rows in each area. The test of young specimens is 

 usually ornamented with spirally arranged bands of color, extending across 

 the ambulacral and interambulacral areas in disconnected patches, the bands 

 growing narrower towards the abaetinal pole (B. bizonata, Des.). With in- 

 creasing age these bands become more and more indistinct, and can often be 

 but faintly traced in the largest specimens examined. In larger specimens 

 the arrangement of the pores is in three apparently independent vertical 

 rows ; the size of the pores of the same specimen varies greatly in the 

 different ambulacra, and even in the different vertical rows of the same porif- 

 erous zone, either the inner or the outer row having the exterior pore the 

 largest (B. heteropora, Des.). In what has been considered usually the 

 typical T. pileolus the arrangement of the pores is uniform, preserving more 

 persistently the original arrangement of the pores, though the two outer 



