OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 35 



Family GORGONOCEPHALIDAE. 



ASTROTHAMNUS DEFICIENS, new species. 



Plate 1, figs. 1-10. 



Locality. — Albatross station 5605, Gulf of Tomirii, Celebes; Do- 

 depo Island (W.) bearing N. 14° W., 10.93 kilometers (5.9 miles) 

 distant (lat. 0° 21' 33" N., long. 121° 34' 10" E.) ; 1,183 meters 

 (647 fathoms) ; November 16, 1909. 



One specimen (Cat. No. E. 158, U.S.N.M.). 



Description. — The specimen unfortunately is not in a very good 

 state of preservation; the arms are broken up into numerous frag- 

 ments, and two of them are entirely lacking. However, poor as it 

 is, it can be satisfactorily studied and described, and it is evident 

 that it can not be referred to any known species. 



The diameter of the disk is 21 mm.; the arms must have had a 

 length of between 120 mm. and 140 mm. They are unbranched for 

 their entire length. The disk is thick and reaches 6.5 mm. in height. 

 The dorsal surface is depressed in the central region, and the ventral 

 surface is strongly convex; the radial and interradial regions are 

 strongly excavated at the periphery. The arms at their bases are 

 very distinct from the disk; they measure 5.5 mm. in width and 

 6 mm. in height ; they taper very gradually, but their height always 

 remains a little greater than their width. Their dorsal surface is 

 strongly convex, and by strongly rounded borders passes over into 

 the sides, which are vertical ; their ventral surface is almost flat. 



On the dorsal surface of the disk there are 10 much-elevated ribs, 

 which arise in the central region and, progressively increasing in 

 height and width, reach the periphery. The two ribs of each pair 

 are strongly divergent, and at the periphery of the disk they are 

 separated from each other by an interval of about 7 mm., within 

 which lies the base of the arm. The border of the disk is rather 

 strongly excavated between the extremities of the radial ribs, and 

 these on either side pass beyond the base of the corresponding arm.' 

 The radial spaces between the two ribs of each pair and the inter- 

 radial spaces between the pairs are rather strongly depressed. The- 

 whole dorsal surface of the disk is covered with small and thin., 

 though not transparent, plates, which are more or less imbricated, 

 irregularly polygonal, with the free border slightly raised, and 

 which become larger over the radial ribs where they are about 1 mm. 

 in diameter; they are smaller in the radial spaces, becoming still 

 smaller in the interradial spaces. Their dimensions still further 

 decrease toward the center of the disk, and they finally become 

 excessively reduced in the central region. Over the radial ribs some 

 of these plates are raised up into a large conical and pointed tubercle, 



