OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 293 



part is rather variable ; it is rather large and triangular in shape in 

 the specimen represented on plate 44 as figure 3, less extensive on 

 that represented in figure 7, and still smaller on that in figure 6, where 

 this naked portion is small and oval. The two shields of each pair 

 are rather strongly divergent. The plates of the dorsal surface of 

 the disk may carry small, short, and rounded granules which often 

 show a tendency to rise up into small pointed cones (pi. 44, fig. 6, 

 and pi. 103, fig. 9b). In other specimens a certain number of 

 granules transform rather abruptly into spines which are rather 

 large, elongated, stout, and pointed, and are furnished with asperities 

 or even with small irregular teeth. These spines may be very few in 

 number and relatively small (fig. 3), or they may become very abun- 

 dant and very strong, rather thick, long, and pointed, with the sur- 

 face rugose or denticulated (fig. 7). The spines or the granules 

 continue over a small portion of the ventral surface of the disk but 

 they never advance very far, and the major portion of this surface 

 remains naked. The genital slits are large and broad; the genital 

 plates are extremely large. 



The mouth pieces are only slightly developed. The mouth shields 

 are small, broader than long, triangular or lozenge-shaped, with an 

 obtuse proximal angle sometimes prolonged a little toward the mouth 

 and bordered by two slightly excavated sides; the distal border is 

 very convex and is often broken up into two short sides united by a 

 very obtuse and rounded angle. The adoral plates are elongated, 

 broader outwardly than inwardly, and they usually send off a process 

 which separates the mouth shield from the first side arm plate; 

 they taper inwardly, but are in contact in the median interradial line. 

 The oral plates are of medium size. The tooth papillae are much 

 developed ; there can usually be recognized two lateral rows, and in 

 addition a median cluster composed of three very irregular rows. 



As I said above, the arms are very long, but very slender; their 

 dorsal surface is quite plane. The upper arm plates are very large 

 and extremely broad, and they cover almost the whole dorsal sur- 

 face of the arms. They are very much broader than long, with the 

 two long sides almost parallel ; the proximal border, which is almost 

 straight, is a little shorter than the distal border, which is sometimes 

 straight, and sometimes a little convex, and in the large specimens is 

 very often slightly excavated in the middle; the sides are a little 

 divergent, and they pass over to the distal border by sharp angles. 

 The form of these plates is somewhat inconstant, as may be seen 

 from the photographs which I give (pi. 44, figs. 3-7), and theset 

 plates may be broken up into fragments, of which the form, the 

 dimensions, and the number are extremely variable; in this respect 

 the greatest differences are found in different specimens, and in dif- 

 ferent arms of the same specimen, or even in different parts of a 



