OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 71 



Albatross agree well with the Siboga specimens, and they also show 

 in the covering of the dorsal surface of the disk variations similar 

 to those which I have already had occasion to notice. There may 

 be club spines terminating in many unequal spinules, or long and 

 slender true spines either with long spinules along their entire 

 length or simply with very much shorter teeth. These spines are 

 shown especially well on the two specimens from station 5423. There 

 occur also forms intermediate between the club spines and the true 

 spines, as may be seen on the photographs which I give in figure 7 

 on plate 93. On the two specimens from station 5423 the dorsal sur- 

 face bears among the granules very fine and short true spines having 

 a length of about 0.5 mm., which may occur as far as the periphery 

 of the disk. The surface of the upper arm plates is always rugose, 

 and the asperities retain more or less strongly the particles of mud 

 which adhere to them. These asperities may be localized chiefly on 

 the distal edge of the plates, there forming a small and very evident 

 border, which, however, always remains formed of simple rugosities. 



I give here a photograph of the large specimen from station 5648 

 (pi. 8, figs. 5,6). 



Ophiotreta eximia, it seems to me, may be assigned to Verrill's 

 genus Ophiotreta, together with O. dilecta (Kcehler), O. lineolata 

 (Lyman), and O. sertata (Lyman), and the species which I will 

 mention below, O. gratwsa, O. matura, O. spatulifera, and 0. valen- 

 ciennesi. I recognize the fact that the genus Ophiotreta has no 

 great value and is scarcely more than a subgenus of Ophiacantha. 

 But this division of Ophiacantha proposed by Verrill is nevertheless 

 convenient. H. L. Clark has maintained it in his catalogue ('15, 

 p. 216), but Matsumoto, in 1917, did not distinguish it from the 

 genus Ophiacantha. 



I should state that I adopt the genus Ophiotreta with the char- 

 acters and with the limitations given to it by Verrill and not in 

 H. L. Clark's sense. The latter assigns to it O. mixta (Lyman) and 

 O. littoralis (Kcehler), which should be placed in Matsumoto's 

 genus Ophiurochocia (see on this subject Matsumoto, '17, pp. 

 316,317). 



OPHIOTRETA GRATIOSA (Kcehler). 



Plate 11, figs. 1-7 ; plate 95, fig. 1. 



Ophiacantha gratiosa Kcehler ('96), p. 346, pi. 8, figs. 60, 61; ('99), p. 56, 

 pi. 8, fig. 68; pi. 9, figs. 71, 72.— H. L. Clabk ('15), p. 199. 



Ophiacantha inutilis Kcehler ('04), p. Ill, pi. 21, figs. 6-8. — H. L. Clark 

 ('11), p. 208; ('15), p. 199.— Matsumoto ('17), p. 117. 



Localities. — Albatross station 5116; Balayan Bay and Verde 

 Island Passage; Sombrero Island bearing N. 69° E., 4.63 kilometers 



