62 Proceedings of the Biological Society of Washington. 



ated on the border of the disk as viewed abactinally; it bears a few small 

 spinelets about its border. 



The papulee are very large, abundant, and conspicuous, covering the 

 dorsal surface of the disk and arms, and the lateral surfaces of the latter; 

 on the sides of the arms they are arranged in regular diagonal lines; in 

 the midradial region of the arms and on the disk their arrangement is 

 irregular. 



There are no traces of any plates between the adambulacrals and the 

 actinal border of the dorsal meshwork. 



The adambulacral plates at first are about twice as broad as long, be- 

 coming about as long as broad after the proximal third of the arm ; each 

 of these plates is separated from its neighbors by a distinct interval or 

 suture. 



The adambulacral plates bear within the furrow three long and very 

 slender spines situated one above the other ; on the furrow margin there 

 are usually three longer and stouter spines, forming a furrow comb; these 

 may be arranged with the central one in advance, or they may (more 

 rarely) stand in a diagonal line with the outermost nearest the center of 

 the furrow ; the innermost spine on the furrow margin ( whether the first 

 or the second) is directly over the slender furrow spine. The typical 

 arrangement seems to be, middle one in advance, proximal one slightly 

 behind it, distal one considerably behind it. The middle one, which is 

 larger than the others, is more or less sabre-shaped. The actinal surface 

 of the plate is studded with small spinelets which are irregular in position. 



The mouth plates are large and, owing to the absence of actinal inter- 

 mediate, or other except adambulacral, plates, very conspicuous. The 

 mouth spine.s are five in number, resembling the spines on the border of 

 the adambulacrals. On the outermost angle, deep in the furrow, are two 

 more spines, much smaller and more slender, of which the proximal is 

 opposite the fifth of the furrow series, and the distal, which is slightly 

 smaller, is situated slightly beyond. The inner half of the mouth plates 

 is covered with small spinules, but the distal half is naked. 



Color in alcohol brownish white. 



Type.—Ga.i. No. 38,316, U. S. N. M., from "Albatross" Station 2993, 

 oflF the Revillagigedo Islands, Lower California, in 364 fathoms. 



