OPHITJRANS OF THE PHILIPPINE AND ADJACENT WATERS. 489 



the free border rounded ; it is inserted both on the oral plate and on 

 the adoral. The following papilla is very much smaller, almost 

 quadrangular, and a little broader than long ; the three following are 

 small, conical, and pointed, but the proximal papilla is stronger, and 

 almost of the same size as the unpaired papilla which terminates the 

 yaw, and which is also conical and pointed. Beyond the outermost 

 mouth papilla there is a papilla inserted on the first under arm plate 

 which is much elongated, narrow, pointed, and slightly recurved. 



The arms are rather broad at the base, and when they are viewed 

 from the ventral surface, it may be seen that their width increases 

 progressively and rather rapidly as far as the border of the disk, 

 then decreases very much more gradually. 



The first upper arm plate is very small, triangular, with the angles 

 rounded. The second, which is larger, is trapezoidal with a narrow 

 proximal border and very divergent sides. These two plates are 

 always included in the radial incisions of the disk. The third plate 

 is very much larger than the preceding; it is trapezoidal, also with 

 divergent sides, and two and a half times as broad as long. The 

 granules of the dorsal surface of the disk stop at a variable level on 

 this plate, and sometimes they reach its distal border. The following 

 plates are quadrangular, very much broader than long, with straight 

 borders ; the proximal border is a little narrower than the distal, and 

 the sides are slightly divergent. 



The first under arm plate is short and very much broadened, at 

 least three times as broad as long; its proximal border, which is very 

 broad, curves outwardly and passes over by sharp angles to the short 

 and oblique sides; the distal border is straight and as broad as the 

 proximal side of the second plate. The following plates are quad- 

 rangular, broader than long, with the proximal border straight ; the 

 distal border, which is a little broader, is very slightly notched in 

 the middle and rounded on either side of the notch; the sides are 

 broadly excavated by the tentacle pores and they pass over into the 

 distal border by sharp angles. 



The side arm plates, which are not very projecting, carry at the 

 base of the arms eight spines; this number soon falls to seven and 

 then to six. These spines are slender, flattened, broadened, and 

 pointed, more or less lanceolate in form, and appressed against the 

 side arm plate. The three or four first ventral spines have almost the 

 length of the segment, the following little by little become shorter, 

 and the last only reaches a length of half a segment. 



The tentacle scales are two in number throughout the whole length 

 of the arms; they are- very large and oval; the internal scale is a 

 little larger than the external, which it slightly overlaps. 



