OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 21 



The outlines of the mouth plates are fairly well seen in the dried 

 specimens, such as that which I have shown in figure 8. The mouth 

 shields are large and broad, very much broader than long, triangular, 

 with a very obtuse and rounded proximal angle similarly broadly 

 rounded lateral angles, and a convex distal border. The -adoral 

 plates are much elongated, narrowed inwardly, but usually reaching 

 the median interradial line ; outwardly they are broadened and give 

 off a narrow process which separates the mouth shield from the first 

 side arm plate. 



The lateral mouth papillae are four in number in both specimens ; 

 they are unequal, and always arranged in a slightly irregular man- 

 ner, as I stated in 1904. The only papilla of which the form is 

 fairly constant is the proximal, which is rounded, slightly denticu- 

 late on its free border, and very much smaller than the terminal 

 papilla; the three others are conical, pointed, and of medium, but 

 variable, dimensions. 



The arms are narrow and rather flexible. The shape of the upper 

 arm plates recalls that which I have just described in Ophiomyxa 

 irregularis. The under arm plates are as broad as long, with a 

 rather sharp proximal angle, straight sides, and a deeply notched 

 distal border; this border even projects rather strongly on either 

 side of the notch which is then delimited by two small acute angles, 

 becoming thereby very evident. These plates are separated by a 

 rather narrow interval which, however, is well marked from the 

 second arm segment outward. 



As a rule the arm spines are three in number, and sometimes even 

 only two; I have only seen four very rarely, and only on the first 

 arm segments. These spines are moderately thick at their base, 

 which is buried in the integument, thence tapering very rapidly and 

 becoming rather slender and pointed; they bear denticulations only 

 in their distal half, and these are not very strongly developed (pi. 

 92, fig. 3a). The two ventral spines equal or slightly exceed half 

 the length of the segment ; the dorsal spine is a little longer, though 

 it does not reach quite the length of the segment. As the arms be- 

 come narrower the denticulations of the spines, which are rather 

 poorly developed at the base of the arms (pi. 92, fig. 3#) become 

 stronger (fig. 35) ; they are often more developed along one of the 

 borders of the spine, and thus the first ventral spine sometimes takes 

 a form approaching that of a hook, though it can not be said that, 

 it becomes converted into a true hook. 



I was greatly surprised to find in the integument of O. neglecta 

 both on the disk and on the arms C -shaped spicules analogous to< 

 those known in various echinoids and holothurians ; some of these' 

 are here figured (fig. 3^). 



