OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 291 



and the radial shields, which are exposed over their entire area, may 

 be clearly distinguished. In others, as that which is represented in 

 figure 8, and which I have just mentioned, the spines are shorter and 

 thicker, and the dorsal surface of the disk is covered with a fairly 

 developed integument which more or less complete^ conceals the 

 underlying plates and encroaches more or less upon the radial shields. 



The specimen from station 5080 (fig. 6) is remarkable for the 

 rudimentary condition of the armature of the dorsal surface of the 

 disk; the club spines are not very numerous, and are of small size, 

 conical, and well spaced; they become a little stouter and a little 

 more numerous toward the periphery of the disk. In its general 

 appearance this specimen quite brings to mind an O phiogymna pel- 

 licula, but the characters of the upper arm plates do not permit of 

 referring it to that form. 



The upper arm plates only show variations in form of slight im- 

 portance; they are always trapezoidal, with a fairly straight and 

 slightly concave proximal border, and a very broad and strongly con- 

 vex distal border, usually made up of two short sides united by an 

 obtuse angle; the lateral borders are straight and divergent, and 

 they pass to the distal side over rounded angles; these plates are 

 relatively more elongated in the young where they are still, however, 

 broader than long. The upper arm plates have the form of a dihe- 

 dral angle with a more or less well marked dorsal keel, and usually 

 they show toward the middle, but a little nearer the distal border, a 

 rather broad rounded and flattened tubercle, which sometimes is de- 

 tached from the general surface of the plate on which the keel is 

 only slightly visible, and sometimes is continuous with the keel itself, 

 which is more strongly marked. The presence of small granules on 

 the surface of the upper arm plates is rather rare in the Albatross 

 specimens and occurs very irregularly. One of the specimens on 

 which they are found rather abundantly is that from station 5141 

 which I show on plate 42 as figure 1. The form of these granules, 

 which are somewhat conical, pointed, and rather fine, may be seen 

 on the arm shown in profile; they occur only in the proximal half 

 of the arms. On other specimens a few granules may be met with 

 which are sometimes conical, sometimes rounded, always few in 

 number, and occurring in a very irregular manner exclusively in the 

 proximal region of the arms; I include a figure (pi. 43, fig. 10) of 

 the dorsal surface of the arm of a specimen from station 5545 which 

 shows a few of these rounded granules. 



The arm spines are rather large, comparatively short in the small 

 specimens, but their length increases proportionately with the size, 

 of the individual. In specimens of small and of medium size the 

 lateral spines have the tip somewhat broadened and very rounded; 

 in the large this tip is always rounded, but it is onlv slightlv or not 



