160 NATURAL HISTORY BULLETIN 



superomarginal plates, which are evenly rounded vertically, 

 densely granulated, and separated by deep and wide fasciolated 

 grooves, clothed with innumerable fine spinules. On the distal 

 half to three-fourths of the ray these plates bear, on the outer 

 convex surface, a single small obtuse-conical spine. These spines 

 rarely extend to the base of the ray. Paxillar spinules are 

 crowded and capitate or clavate. 



Inferomarginal plates bear two flattened, short, marginal 

 spines, side by side, and a row of about four on the under side, 

 near each margin, the aboral ones larger ; between these the sur- 

 face is closely crowded with small, flat, more or less scale-like 

 spinules. 



The adambulacral spines are triseriate or nearly so ; inner ones 

 are usually three, somewhat flattened ; the next row has two flat 

 spines, side by side, the aboral one larger. Sometimes there is a 

 third spine; outer ones are four to six, small, flat, or spatulate 

 spinules, either in one or two rows, or clustered. 



Special description : A well grown normal specimen agreeing 

 well with Say's type, is from Egmont Key, W. Florida (No. 

 2213, Yale Mus.). 



Its radii are 17°^™ and 76™^ ; ratio, 1 :4.5 ; breadth of rays at 

 base, without spines, 20°"°^ with spines, 25™™ ; breadth of paxillary 

 area at second pair of superomarginal plates, 10™™; breadth at 

 10th pair, 8™™ ; radius of disk is equal to first six or six and one- 

 half marginal plates ; height of second marginal plate is equal to 

 length (radial) of three (2d to 4th). Number of marginal 

 plates, 27-28 pairs. 



The rays are thick and stout with rather blunt tips. The oc- 

 ular plate is relatively large, turned up, short and thick, as wide 

 as long, deeply bilobed, and grooved above with the sides swollen. 

 Paxillary area broad, even. 



The superomarginal plates are larger, and thick, well rounded 

 transversely, not at all obliquely placed, except slightly near tip 

 of rays. The first or interradial pairs are thicker and higher 

 than the following, and wedge-shaped. 



A single imperfect row of small, short, obtuse-conic or acorn- 

 shaped spines is present on the distal two-thirds or three-fourths 

 of the ray, extending on some of the rays to the fifth plate from 

 the base, and to the last pair of plates at the tip of the ray. 



