OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 803 



Description. — The diameter of the disk is 3 mm. ; the arms are from 

 15 mm. to 18 mm. long. 



The disk is rounded. The dorsal surface is covered with few plates, 

 among which a circular dorso-central which is very much larger than 

 the others may be distinguished. These plates form five broad inter- 

 radial bands in which they are arranged in two or three rows ; they 

 are rounded or oval, somewhat unequal, and those which are close to 

 the dorso-central plate are larger than the others. Toward the 

 periphery of the disk the plates become rapidly very much smaller 

 and more numerous, and they cover a semicircular space which pro- 

 jects outward between the arms, encroaching upon about half the 

 length of the distal border of each radial shield. The dorsal plates 

 of the disk are without club spines, and these only occur at the 

 periphery of the disk on the plates of the latter, or on those of the 

 two last rows, whence they continue onto the ventral surface. The 

 club spines are short, rather thick, ending in three or four triangular 

 and very short spinules. The radial shields are triangular and rather 

 small ; their length equals about half the radius of the disk, and they 

 are almost twice as long as broad ; the two shields of each pair are 

 slightly divergent and close together, though not in contact, out- 

 wardly and separated by a single row of plates. 



The ventral surface of the disk does not show distinct plates, but 

 it is covered over its whole extent with club spines which are more 

 developed than those seen at the periphery of the disk on viewing 

 the ophiuran from the dorsal surface, and these club spines all termi- 

 nate in three or four short and triangular spinules. 



The mouth shields, which are broader than long, are lozenge- 

 shaped, with the angles rounded. The adoral plates are triangular 

 with the apex rounded ; they are in contact in the median interradial 

 line, and they broaden progressively outwardly. The oral plates are 

 high. The tooth papillae are arranged in three rows only, two 

 lateral and a median. 



The upper arm plates, which are large and broad, are trapezoidal 

 with a straight and slightly concave proximal border, and a broad 

 and convex distal border passing over by rounded angles into the 

 sides, which are very slightly concave. All these plates are broadly 

 in contact. 



The first under arm plate is small, rectangular, and broader than 

 long. The following plates are rectangular, at first as broad as 

 long, then becoming a little longer than broad, with the sides slightly 

 convex and the angles rounded. They are very broadly in contact. 



The side arm plates carry eight spines at the base of the arms. 

 The four ventral spines are free. From the commencement of the 

 arms the first assumes the form of a hook which usually shows onlv 



