OPHIUKANS OF THE PHILIPPINE AND ADJACENT WATERS. 401 



In this same example from station 5259 I find a peculiarity which 

 is also found in the small specimen from the same station and which 

 I have not found in any other. At each of the angles of the distal 

 border of the mouth shield there occurs a very small intercalated 

 plate which causes this angle to be somewhat truncated. This plate 

 is very constant and is lacking only in one of the angles of the mouth 

 shield of the large specimen. The appearance of this plate is not 

 correlated with the age of the subject, as I find it both in the small 

 and in the large specimen, and it is lacking in the other large speci- 

 mens. But I find an indication of it in the form of two very small 

 plates in the specimen from station 5527. 



The mouth shields are large, a little longer than broad, pentagonal, 

 with a sharp proximal angle bordered by straight sides, two convex 

 and slightly convergent sides, and a straight distal border. The 

 adoral plates are large, rather short, twice as long as broad, much 

 broadened in their outer half, and tapering inwardly. The oral plates 

 are triangular and high. The lateral mouth papillae are six in 

 number; they are large and rather broad, especially the outermost, 

 which is very highly developed, rectangular in form, and broader 

 than long; the four following are almost square, and the last is 

 conical and pointed : the unpaired terminal papilla is slightly stouter 

 than the preceding. 



The first upper arm plate is rectangular, broader than long, with 

 the distal border convex. The following are small, triangular, a 

 little broader than long, and their size decreases very rapidly ; they 

 are all widely separated. 



The first under arm plate is small, pentagonal, almost as broad as 

 long, with a rather sharp proximal angle. The two following are 

 rather large, elongated, pentagonal, with a sharp proximal angle; 

 the} 7 are widely separated ; the third is a little broader than the sec- 

 ond. Beyond this the plates become extremely small, but they are 

 continued over the greater part of the length of the arms. 



The side arm plates are projecting and strongly swollen in their 

 distal dorsal region ; they are covered with granules similar to those 

 of the dorsal surface of the disk, but somewhat less evident; these 

 granules soon disappear; and they are, moreover, very unequally 

 developed in different specimens. The arm spines are four in num- 

 ber; the two first form a small group close to the ventral border of 

 the plate, and the second is twice as broad as the first ; the two others, 

 somewhat separated from each other and from the small group 

 formed by the two preceding, are smaller and thinner; they are at 

 first some distance from the distal border of the plate on the first 

 arm segments, then little by little they approach that border. I some- 

 times find at the base of the arms three ventral spines instead of 

 only two. 



55269 22 Bull. 100 26 



