570 Verrill, N'utes on Radiata. 



and less regularly arranged, forming clusters rather than rows, and ex- 

 tend backward beyond the fasciole, nearly to the anal area. The plas- 

 tron is broad oval, emarginate behind, the sides pretty regularly curved. 

 The subanal area is broadly cordate, with three or four conspicuous 

 pores on each side, from each of which a well-marked groove extends 

 to the center. The fasciole surrounding it is broad and well defined ; 

 the branches extending up near the sides of the anal area are nar- 

 rower, but depressed and conspicuous. The anal area is large, nearly 

 circular, but with a sharp angle on the upper side ; moi'e than half of 

 its diameter is occupied by a thin central membrane, which is some- 

 what semicircular, rounded below, its surface toward the edge bear- 

 ing minute, scattered, rounded plates, which, nearer the edge, increase 

 in size and form two or three disconnected circles of detached plates. 

 These are mostly rounded, or more or less oblong, though quite irreg- 

 ular in form and size, but the outer rows are composed of successively 

 larger and closer plates. Those of the outermost row are considera- 

 bly the largest and are mostly in contact, though still quite irregular 

 in size and form, and mostly with rounded angles and sides ; on the 

 upper side there is a triangular group of four or five similar plates, 

 between the outermost row and the small plates of the inner circles. 

 The actinostome is very broad crescent shaped, with rounded corners, 

 not at all produced, or even slightly emarginate, anteriorly ; but it is 

 strongly labiate, the lower border much thickened, prominent, and 

 broadly rounded. The actinal area is occupied by a thin membrane, 

 which bears comparatively few (about 25), mostly large and discon- 

 nected, irregularly shaped plates, most of which are not in contact ; 

 the larger ones are pierced by one or two pairs of small pores, and 

 the marginal ones bear a few small miliary tubercles. The outer row 

 contains 9 or 10 plates, which are transversely oblong and very une- 

 qual in size and form, but mostly in contact at their ends ; inside of 

 these there is an irregular row of 8, large, irregularly rounded plates, 

 which are mostly not in contact, often leaving considerable spaces of 

 naked membrane between. The inner portion of the membrane bears 

 an irregular group of five or six, unequal, smaller, well separated, 

 rounded plates. 



The largest specimen is 6-50 inches long; 5-35 broad; 2*05 high; 

 length of anterior lateral ambulacra from apex 2-35; greatest breadth 

 •38; length of posterior ones 2-80; breadth -45; diameter of largest 

 ovarial pores '09 by "05 ; average breadth of fasciole, about '06 ; 

 length of plastron 3-35 ; breadth 1*35; transverse diameter of anal 

 area -58; longitudinal diameter -65 ; diameter of its largest plates -08 



