OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 31 



as broad, and do not separate the mouth shield from the first side 

 arm plate ; they are not in contact in the median interradial line, but 

 are separated by a rather broad space which is similarly continued 

 between the oral plates and which is simply covered by integument. 

 The oral plates are very high, elongated and narrow, three times as 

 high as broad, and directed obliquely toward each other; they are 

 separated for half of their length by the space which I have just 

 described and are in contact only in their proximal half. There are 

 two mouth papillae; the outer is small, short, and rounded, with a 

 rugose surface, situated on the internal border of the mouth tenta- 

 cle pore; the other, which is near the proximal end of the oral 

 plates, is elongated, pointed, spiniform, and conical, and its surface 

 is more rugose than that of the preceding. The teeth, which are 

 spiniform and elongated, form a regular double vertical column, 

 below which are some dental papillae of the same form; these last 

 are usually three in number, a larger unpaired papilla and two 

 smaller lateral papillae. 



The upper arm plates are entirely lacking. The first under arm 

 plate is large, rectangular, greatly broadened transversely, almost 

 three times as broad as long. Those following are very large, rec- 

 tangular, almost as broad as long, and all in contact. On the first 

 arm segments their distal border is more or less strongly notched 

 in the middle, and their sides extend inward somewhat obliquely; 

 they then become regularly quadrangular, and a little broader than 

 long. In the specimen from station 5592 these plates are more 

 broadened, and their distal border remains concave over a large part 

 of the length of the arms; furthermore, they are usually separated 

 by a narrow space filled by soft tissue. 



The side arm plates, which are very narrow on the ventral side, 

 carry four much elongated, slender, and transparent arm spines, 

 which are furnished with very strong and closely crowded teeth; 

 these spines much exceed the length of the segment, and the two 

 central spines, which are a little longer than the others, may reach 

 a length of two segments. 



In figure 1 on plate 93 I have given figures of some arm spines 

 taken from different heights along the arm. Toward the extremity 

 of the arms the teeth, relatively very strong and well spaced, are 

 often more developed on one of the borders than on the other (fig. 

 1&), but the first ventral spine is never converted into a true hook, 

 and sometimes it even entirely lacks the denticulations (fig. 1<?) . 



The tentacular pores are extremely large and do not show the 

 least trace of a scale. 



In the specimen from station 5592 the disk is dark brown in color, 

 even blackish, on the dorsal surface; the arms are a little lighter; 



