OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 225 



Can there be a relation between age, or perhaps even between the 

 sex, of the individuals and the transformation of the dorsal spine? 

 Are all the individuals destined to undergo this transformation or 

 does it only take place accidentally and then under the influence of 

 certain conditions ? These are questions which I can not answer. 



OPHIOTHRIX DECEPTOR, new species. 



Plate 58, figs. 1, 2 ; plate 97, fig. 6. 



Locality. — Albatross station 5414; between Cebu and Bohol; Lauis 

 Point Light bearing N. 67° W., 17.60 kilometers (9.5 miles) distant 

 (lat. 10° 10' 40" N., long. 124° 02' 45" E.) ; no depth given; March 

 24, 1909. 



One specimen (Cat. No. E.13, U.S.N.M.). 



Description. — The diameter of the disk is 5 mm. ; the arms are thin 

 and slender, from 30 mm. to 32 mm. long. 



The disk is subpentagonal, with the sides slightly excavated. The 

 dorsal surface between the very large radial shields is covered with 

 very small unequal plates rounded in the central region and becom- 

 ing elongated and extremely narrow in the interradial spaces; the 

 outlines of these plates are not very evident, for they are covered 

 by a thin integument. A certain number bear a rather large, pro- 

 jecting granule, which is somewhat conical, with the extremity 

 rounded. At the periphery of the disk, outside the radial shields 

 and in the interradial spaces, the plates become very thin and trans- 

 parent, short and transversely broadened, and they form a continu- 

 ous covering on which may be perceived here and there a very small 

 conical and pointed granule which is very much smaller than those 

 of the rest of the dorsal surface. The radial shields are very large 

 and they cover a large part of the dorsal surface of the disk; the 

 radial and interradial spaces are very narrow. The two shields of 

 each pair are in contact by their external angle, thence separating 

 slightly, especially because of the slightly concave form of their 

 internal border ; the outer angle of each shield is separated from the 

 corresponding angle of the shield of the neighboring pair by a very 

 narrow interval ; from that point onward the interradial spaces pro- 

 gressively increase somewhat. The shields themselves are triangu- 

 lar, with a pointed proximal angle and a concave distal border ; they 

 are longer than broad, and their length reaches or exceeds two-thirds 

 of the radius of the disk. Their surface is entirely naked. 



The ventral surface of the disk is covered with extremely small, 

 thin, transparent, slightly imbricated, and very narrow plates. The 

 genital slits are broad and very evident. 



The mouth shields are short and much broadened, almost three 

 times as broad as long, with a rather sharp proximal angle projecting 

 55269— 22— Bui. 100 15 



