448 PROCEEDINGS OF THE NATIONAL MUSEUM vol.86 



part of the surface of the disk is occupied by 5 pairs of large radial 

 shields. The two shields of each pair are separated by a single 

 somewhat irregular row of moderate-sized obscurely delimited scales. 

 The pairs of shields are separated interradially by about 3 rows of 

 scales with similarly indefinite borders. The scaled central portion 

 of the disk, a circular area with a diameter equal to about one-fourth 

 that of the disk, the narrow radial line of scales, and the broad inter- 

 radial bands are uniformly studded with short, thick, subconical 

 stumps with blunt spinulose tips that on superficial examination 

 appear like granules. In the central circular area there are about 

 40 of these; a single somewhat irregular row runs along the lines 

 of scales separating the radial shields of each pair; and there are 

 about 3 irregular rows at the inner ends of the interradial bands 

 of scales, this number increasing to about 6 at the edge of the disk. 

 Each scale seems to carry a single stump. The radial shields bear 

 1 to 5 widely and irregularly scattered stumps. The interbrachial 

 areas on the oral surface are naked except for 3 or 4 large, rounded, 

 and well-defined scales in the central portion, one or two of which 

 may bear centrall)^ situated stumps. 



The 5 short arms are 13 mm long. The upper arm plates in- 

 crease in size to the fourth, which is triangular with the proximal 

 angle very broadly and the lateral angles more abruptly rounded, 

 not quite twice as broad as long. The upper arm plates following 

 gradually increase in length, the angle between the lateral edges at 

 the same time decreasing, so that at the middle of the arm they are 

 about as long as broad. Distally they become very narrow, elongate 

 fan-shaped, much longer than broad, with rounded lateral angles, 

 remaining always in contact. The surface of the upper arm plates 

 is finely pustulate. 



The oral shields are nearly twice as broad as long, rhombic with 

 concave sides, the lateral angles rounded and the outer and imier 

 angles pointed. 



The adoral plates are triangular, about twice as long as the width 

 of the radial ends, with their apices just meeting under the inner 

 side of the oral shields. Their outer border is closely appressed 

 to, and of the same length as, the adjoining side of the oral shield. 



There are 9 rather short and stout tooth papillae, a column of 4 

 on each jaw plate and a median one. 



The under arm plates are quadrilateral with the proximal and dis- 

 tal angles rounded, the distal border strongly concave, and the proxi- 

 mal somewhat convex. They are at first broader than long, becoming 

 about as broad as long in the middle of the arm and elongate dis- 

 tally. In the earlier portion of the arms the proximal border is 

 more or less angulate centrally. 



