OPHIUKANS OF THE PHILIPPINE AND ADJACENT WATERS. 155 



limited to the two proximal sides of the mouth shields ; they are very 

 narrow inwardly and do not reach the interradial median line; out- 

 wardly they become much broadened and send off a narrow process 

 which separates the mouth shield from the first side arm plate. The 

 oral plates are twice as high as broad, but they are in contact only 

 in their proximal half; they thus delimit a naked triangular space, 

 of which the base is formed by the proximal extremities of the 

 mouth shield and the adoral plates. The terminal mouth papilla is 

 rather thick, almost cubical, with the proximal face channeled. The 

 second papilla, inserted on the oral plate, is elongated, conical, with 

 the point blunted; the external papilla, inserted on the adoral plate, 

 is broadened, sometimes rounded and sometimes triangular, with the 

 tip much blunted. 



The upper arm plates are very large, covering the greater part of 

 the dorsal surface of the arm. They are semicircular or almost bi- 

 convex, with a somewhat rounded distal side, and are very much 

 broader than long ; all of them are in contact. 



The first under arm plate is small, trapezoidal, with a narrow distal 

 border, a longer proximal border, and divergent sides. The follow- 

 ing plates are -pentagonal, a little longer than broad, with a trun- 

 cated and rounded proximal angle, the lateral borders slightly 

 notched by the tentacle scale, and the distal side slightly excavated 

 in the middle. They are all in contact. 



The side arm plates, which are only slightly projecting, bear five 

 subequal spines, the length of which almost equals that of the seg- 

 ment; this number falls to four at some distance from the base. 

 These spines are rather thick and cylindrical, with the tip rounded ; 

 on the second ventral spine especially the tip is rather thick. Their 

 surface is simply rugose without showing distinct asperities. 



The single tentacle scale is very large, flattened, markedly longer 

 than broad, with the tip rounded. 



The specimen in alcohol is grayish white. 



Affinities and distinctive features. Amphiura dejecta belongs to 

 the section of the genus Amphiura in which the disk is covered with 

 plates on both surfaces, and which only possesses a single tentacle 

 scale. It may be compared with A. dbbreviata Kcehler, A. agitata 

 Koehler, A. angularis Lyman, A. duncani Lyman (=A. liltkeni Dun- 

 can), and A. macraspis H. L. Clark, but it can not be confused with 

 any of these. Amphiura abbreviata has the radial shields very nar- 

 row and elongated, the primary plates distinct, and the arm spines six 

 in number, half of them bihamulate; A. agitata possess seven arm 

 spines, and the dorsal plates of the disk are larger; A. angularis, 

 which has only four arm spines, has the external mouth papilla 

 smaller and the tentacle scale also smaller; A. duncani has six arm 



