THE GENUS COLOBOCENTEOTUS. 13 



than those of that species (Pis. -9^, figs. J.-5; ^, figs. 1-3). The primaries of 



A A A 



the abactinal side of the test are much smaller than those of Podophora 

 and are loosely packed upon the test, leaving considerable open space round 

 each tubercle. This open space is specially marked on the line separating the 

 ambulacral from the interambulacral zones (Pis. 33, figs. 2, 3; 37, figs. 2, 3). 

 The general color* of the radioles is of a grayish pink color with a slight 

 tinge of green on the upper surface of the larger primary ambital radioles. 



Seen in profile and from the abactinal side the primary radioles which are 

 irregularly circular at the tip are seen to diminish very gradually in size above 

 the ambitus as they reach towards the apical system (Pis. 33, figs. 2, 3; 37, 

 figs. 2, S). The large abactinal radioles immediately above the ambitus are 

 arranged more closely than those more distant from it (Pis. 33, fig. 3; 37, 

 fig. 3). 



Seen from the actinal side (Pis. 33, fig. 1; 37, fig. 1), the actinal membrane 

 is nearly bare, carrying but few small clusters of miliary spines on the pairs 

 of poriferous plates and a few minute spines irregularly scattered over it. 

 (Pis. 33, fig. 1; 37, fig. 1). The actinal side of the test below the ambitus is 

 covered with slender somewhat club-shaped spines varying but slightly in 

 shape or size between the actinal system and the actinal side of the ambitus. 

 The poriferous fields are separated by wide interambulacral zones (Pis. 33, 

 fig. I; 37, fig. I). 



The spines of the actinal system close to the teeth are short, club-shaped, 

 slightly flattened (PL 40, fig. 1) ; those from the buccal membrane are some- 

 what longer (PI. 40, fig. 2). Half way between the actinal system and the 

 ambitus the radioles are much stouter and only slightly club-shaped (PI. 40, 

 figs. 3, Jf), as are the smaller spines found on the smaller secondary granules 

 or larger miliaries (PI. 40, fig. 5) ; these spines are all delicately striated with 

 an ill-defined milled ring. 



Below the ambitus we pass suddenly to much larger flattened, angular 

 radioles, rounded at the tip, with a large base for the muscular attachment 

 (PI. 40, figs. 6-8). These spines form a part of the principal subambital 

 fringe of radioles^ the primary radioles of which are figured on PI. 40, 

 figs. 9-11 ; these radioles resemble those of P. jyedifera, but are comparatively 

 shorter and narrower ; they are flat on the lower surface, somewhat spathi- 

 form on the upper surface, and greatly flattened towards the tip of the 

 radiole, as is shown by a profile view (PI. 40, figs. 9, 11). 



We now come to the larger spines of the abactinal pavement immediately 



