OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 355 



animal is plunged into alcohol, and also without doubt to the action 

 of the preserving liquid itself. 



I believe that in saying of the mouth pores that they are very close 

 to or distant from the mouth slits and that they are developed and 

 elongated from the side of tliese slits or, on the other hand, that they 

 are small, narrow, short, and distant from the slits we express condi- 

 tions corresponding to valid characters which are very useful to em- 

 ploy in classification, and not to modifications caused by the action 

 of reagents or the reactions which result from them in the ophiuran, 

 or which are perhaps dependent on the age and on the size of the 

 subject. 



OPHIOPYRGUS PLANULATUS, new species. 



Plate 81, figs. 3, 4. 



Locality. — Albatross station 5613; Gulf of Tomini, Celebes; Buko 

 Buka Island (E.) bearing S. 28° ; 7.41 kilometers (4 miles) distant 

 (lat. 0° 42' 00" S., long. 121° 44' 00" E.) ; 1,375 meters (752 

 fathoms) ; November 20, 1909 ; gy. M. 



One specimen (Cat. No. 40928, U.S.N.M.). 



Description. — The diameter of the disk is 4.4 mm.; the arms are 

 22 mm. long. 



The disk is rather thick; the two surfaces, the dorsal and the 

 ventral, are slightly convex, but the dorsal is not at all elevated; 

 it is entirely covered by six large plates, a dorso-central and five 

 primary radials, without the least trace either of intercalated plates 

 or of radial shields. The dorso-central, which is of very large size, 

 is pentagonal, with straight sides; it covers almost half of the ex- 

 panse of the disk. The radial plates, which are also very large, are 

 trapezoidal, broadened transversely, about twice as broad as long, 

 with a straight proximal side, straight and divergent lateral bor- 

 ders, and a rounded distal border forming the boundary of the 

 periphery of the disk; this distal border is swollen in its central 

 region into a rounded lobe the width of which equals that of the 

 corresponding arm, and which forms a slight prominence above the 

 surface of the disk. The radial papillae are scarcely evident, and, 

 in fact, I only distinguish them at the base of two arms, and only 

 when the animal is viewed from the side or from the ventral sur- 

 face; they are extremely small, conical, and only three or four in 

 number. 



The ventral surface of the disk in the interradial spaces is in very 

 large part covered exclusively by the mouth shields, these being 

 very greatly developed, and there is not the least trace of plates 

 other than the mouth pieces. The mouth shields are triangular, a, 

 little broader than long, with a rather open proximal angle and a 

 very convex distal border forming the periphery of the disk, the 



