40 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



but near tip of ray alternating, there being one more in the series. 

 Each inferomarginal has a low tubercle corresponding to the supero- 

 marginal spine. Viewed from side, both series increase in height 

 from interradius to the sixth plate; thence the superomarginals in- 

 crease slightly in height up to the terminal plate, while the infero- 

 marginals decrease. Beyond the sixth plate the inferomarginals do 

 not encroach upon the actinal surface. The horizontal suture be- 

 tween the two series is not deep. The free surface of the plates is 

 covered with minute bosses. 



Terminal plate very convex, large, elliptical, and wholly dorsal 

 in position, as it lies over the last three superomarginal plates. Judg- 

 ing from the scars of the spines, there are 4 terminal spines placed 

 symmetrically, 2 on either side, and on the narrow summit of the 

 plate, behind these, a series of 3 spines, making 7 in all. 



Cribriform organs spiniform and in the interbrachial arc, continu- 

 ous without a break as far as the middle of the sixth or enlarged 

 superomarginals, except for a slight wedge-shaped area in the middle 

 of the lower edge of each inferomarginal. In each interbrachium 11 

 fused cribriform organs, the odd one over the median interradial 

 suture. The sixth supero- and inferomarginals have a median ver- 

 tical bare space about as wide as the adjacent cribriform organs, 

 "which from here on rapidly narrow, and from the twelfth plate on 

 may be said to be rudimentary. These separated cribriform organs 

 extend upon the dorsal surface of ray and fuse with those of oppo- 

 site side so that the whole area from the limit of paxillae to terminal 

 plate and between the two dorsal rows of spines is a thick continuous 

 mat of spinelets, absolutely identical with the lateral cribriform 

 organs, and a fimbriate channel leads on either side from this area 

 along the lower edge of the terminal plate. The total number of 

 lateral organs is : Rays 9+9+interbrachiuin 11=29. This varies to 30, 

 as some rays have an additional small one at tip. The distal organs 

 are of course rudimentary. The delicate mostly terete spinelets end 

 in a blunt or even capitate fleshy tip (the calcareous part being 

 truncate denticulate). They are very close-set, in regular quincunx, 

 and decrease in length distad, markedly beyond the sixth marginal. 

 The spinelets of the vertical marginal series, in the separated organs 

 are flattened and united by a continuous web ; all other spinelets free 

 and independent. 



Paxillar areas with a stellato-penatagonal contour and comprising 

 the disk and proximal third of ray. Paxillae large, fairly high, 

 crowded, those on rays largest, decreasing in size toward center of 

 disk. The larger paxillae have 15 to 20 peripheral and 5 to 15 central 

 spinelets, cylindrical and slightly knobbed at tip, and one-third to 

 one-half as long as shaft of paxilla, which is variable in thickness but 



