410 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



which are more numerous in O. ligatum than in O. trychnum; these 

 differences have seemed to me important enough to separate from 

 this last the species from the Philippines. 



OPHIOMUSIUM LUNARE Lyman. 



Plate 87, fig. 8. 



Ophiomusium lunare LYMAN ('78), p. 116, pi. 1, figs. 4-6; ('82), p. 84, pi. 1, 

 figs. 13-16. KCEHLER ('04), p. 58. H. L. CLABK ('11), p. 107; ('15), p. 

 330. MATSUMOTO ('17), p. 289. 



Localities Albatross station 5444; east coast of Luzon, San Ber- 

 nardino Strait to San Miguel Bay; Atalaya Point, Batag Island, 

 bearing S. 65 E., 9.45 kilometers (5.1 miles) distant (lat. 12 43' 

 51" N., long. 124 58' 50" E.) ; 563 meters (308 fathoms) ; June 3, 

 1909 ;gn. M. 



Two specimens (Cat. Nos. 41168, 41169, U.S.N.M.). 



Albatross station 5445 ; east coast of Luzon ; San Bernardino Strait 

 to San Miguel Bay; Atalaya Point, Batag Island, bearing S. 56 E., 

 9.82 kilometers (5.3 miles) distant (lat. 12 44' 42" N., long. 124 59' 

 50" E.; 701 meters (383 fathoms) ; June 3, 1909; gn. M., S. 



Two specimens (Cat. No. 40918, U.S.N.M.). 



Notes. The diameter of the disk varies between 10 mm. and 13mm. 



In the arrangement of the dorsal plates of the disk these specimens 

 differ somewhat from the type described by Lyman, but I believe 

 that these differences are due simply to a difference in the size of 

 the specimens. Lyman's type had the disk only 7 mm. in diameter, 

 and the plates were less numerous than in the specimens collected 

 by the Albatross, in which the large plates of the disk, which alone 

 occur in Lyman's type, are separated by a certain number of smaller 

 plates. But I find that the latter are less numerous in the small 

 specimens than in the large, which would confirm my supposition. 

 I have already called attention ('04, p. 59) to similar differences due 

 to age in describing the specimens collected by the Siboga. The two 

 radial shields of each pair are separated for their entire length in the 

 largest specimens, but in the smallest they are in contact by their 

 outer angle, while in Lyman's type they are in contact for half of 

 their length. They are a little larger in my specimens than in the 

 latter. The mouth shields are also a little more elongated. But the 

 other characters are so in agreement with Lyman's description that I 

 do not hesitate to refer my specimens to O. lunare. 



In the specimens which he examined, in which the diameter of 

 the disk varied between 6 mm. and 13 mm., H. L. Clark ('11, p. 107), 

 also found differences correlated with the size of the individuals 

 similar to those which I have noted in the arrangement of the dorsal 

 plates of the disk. I may add also that in the two specimens from 



