OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 101 



rounded angles to unite in a distal border which is similarly rounded. 

 The adoral plates are very large and broad, especially in their ex- 

 ternal portion, and outwardly they extend much beyond the mouth 

 shield which they separate from the first side arm plate. The oral 

 plates are triangular and rather low. The lateral mouth papillae are 

 three in number ; the external is very large, quadrangular, three times 

 as broad as high, and has the form which I have described in the 

 genus Ophioleda; the two others are narrow, conical, and pointed; 

 the unpaired terminal papilla is thick, conical, and rather large. 



The arms are moniliform and made up of relatively much elongated 

 segments. The upper arm plates are triangular, elevated, almost 

 as broad as long, with a proximal angle bounded by two straight 

 sides and a very convex distal border. They are widely separated 

 beyond the first. 



The first under arm plate is small, pentagonal, a little longer than 

 broad, with a sharp proximal angle and straight sides; it is widely 

 separated from the second. The following plates are small, penta- 

 onal, with an obtuse proximal angle, straight sides, and a slightly 

 rounded distal border a little depressed in the middle. These plates 

 are a little longer than broad, and are broadly separated from each 

 other. 



The side arm plates, which project strongly, bear at the base of the 

 arms six rather long, slender, pointed, and finely denticulated spines; 

 the first ventral spine is shorter than the segment, and the last dorsal 

 exceeds a segment and a half. On the two or three first segments 

 the lateral rows of spines come very close together in the dorsal 

 median line of the arm. 



The single tentacle scale is large, elongated, rather narrow, twice 

 as long as broad, with the tip obtuse. 



The color of the specimen in alcohol is white. 



I had already drawn up the description of this species and as- 

 sembled the photographs on plate 23 when I received Matsumoto's 

 first memoir that of 1915. As that naturalist had not, strictly 

 speaking, given any description of 0. venustus, but had only de- 

 termined the differences which separate it from Ophiothamnus 

 (Ophiomitra) hdbrotatus (H. L. Clark), I believed it worth while 

 to give here a description and two photographs of the specimens 

 collected by the Albatross. Matsumoto's final memoir, which ap- 

 peared in 1917, included a detailed description and figures of O. 

 venmtus ('17, p. 126, fig. 32). Not being able at this time to alter 

 my plates, I have allowed the explanation accompanying my photo- 

 graphs to stand. It may also be useful to compare the Albatross 

 specimen with Matsumoto's type, in spite of its smaller size. 



I will add some notes on the subject of the genus Ophiothamnus. 

 Matsumoto has the great credit of dissipating the doubts which 



