OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 361 



sides; the lateral borders are convex and they pass over by very 

 rounded angles to the distal side which is also convex; a rather 

 marked notch corresponding to the bottom of the genital slits sep- 

 arates the anterior region of the shield, which is very short, from the 

 very much more important posterior region. The adoral plates are 

 rather small with the two sides parallel and twice as long as broad. 

 The oral plates are broader and a little shorter than the adoral plates. 

 The lateral mouth papillae are four in number; they are small and 

 low ; the three outermost are rectangular and the last is a little more 

 elongated and conical. The unpaired terminal papilla is conical and 

 a little stronger than those on either side. 



The first upper arm plate is small, trapezoidal, a little broader than 

 long. The following are at first broader than long, quadrangular, 

 with the proximal border narrow and the sides diverging and 

 straight ; the distal border is convex or, better, is formed of two short 

 sides which unite over an obtuse and rounded angle. On the follow- 

 ing plates the proximal border becomes progressively shorter and it 

 disappears at about the twelfth plate ; the plates then become triangu- 

 lar, but always remain a little broader than long; they are at first 

 in contact, later becoming separated by a narrow interval. 



The first under arm plate is rather large, triangular, a little broader 

 than long, with an obtuse and somewhat truncated proximal angle 

 and a very convex distal border. The second is rectangular with the 

 proximal border a little narrower than the rounded distal border. 

 The following plates are pentagonal with a slightly obtuse proximal 

 angle which is truncated on the third and fourth plates, and which 

 is bounded by two concave borders; the sides are straight and they 

 unite over rounded angles to form the distal border, which is also 

 rounded. Little by little the lateral borders disappear, and the 

 plates become simply triangular. They are always broader than 

 long, and beyond the disk they are separated by an increasingly 

 elongated interval. 



The side arm plates carry three small equal papilliform spines; 

 the dorsal spine is separated from the median spine by a space which 

 is a little larger than that separating the latter from the ventral spine. 



The mouth tentacle pores are much elongated and very close to the 

 mouth slits ; they have five scales on each of their borders. The fol- 

 lowing pores have also four or five scales on each border. The num- 

 ber of these scales progressively diminishes and the pores of the sixth 

 pair have two or three proximal scales and a single distal scale. 

 This last finally disappears and there remains only a single proximal 

 scale. 



Affinities and distinctive features. — Amphiophiura fastigiata is re- 

 lated to A. remota and A. latro (Kcehler) collected by the Siboga, 

 and to A. undata (Lyman). The arrangement of the dorsal plates 



