NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM - CLARK. 207 



of which the upper ones are smooth, tapering;, and pointed, while the 

 lower are club-shaped and have rough or thorn}' tips; uppermost 

 longest, equal to two joints or nearly so; distally, the lower arm spines 

 are crowded and turned inward to cover the lower surface of the arm. 

 Tentacle scale single, very small and pointed; those on the first pair of 

 arm pores are larger and blunter than the others, but the difference is 

 not so great as is shown in fig. 966. Color (dried from alcohol), very 

 light brown. 



Localities. Albatross station 3338, off Alaska, lat. 54 19' N.; long. 

 159 40' W., 625 fathoms, green mud, sand, bottom temperature 37.3, 

 3 specimens; station 4781, Bering Sea, lat. 52 14' 30" N.; long. 174 

 13' E., 482 fathoms, fine gray sand, pebbles, bottom temperature 38.6, 

 1 specimen; station 5029, Okhotsk Sea, lat. 48 22' 30" N.; long. 145 

 43' 30" E., 440 fathoms, black sand, gravel, bottom temperature 

 35.3, 1 specimen. Bathymetrical range, 440 to 625 fathoms. Tem- 

 perature range, 38.6 to 35.3. Five specimens. 



Type.C&t. No. 25649, U.S.X.M., from station 5029. 



In some respects, notably the lower arm spines, this species ap- 

 proaches certain forms which I have included (in this report) in the 

 genus Ophiolebes, but the disk and mouth parts are so characteris- 

 tically ophiacanthine that it has seemed to me more natural to include 

 it here. The numerous oral papillaB are a very noticeable feature and 

 the peculiar position of the lo\ver arm spines on the terminal half of 

 the arm is remarkable, at least in the larger specimens. 



OPHIACANTHA DIPLOA, new species.a 



Disk 7 mm. in diameter; arm about 45 mm. long. Disk covered 

 with thorny stumps, among which are some elongated thorny spines 

 almost exactly like those figured by Koehler 6 for duplex. Radial 

 shields narrow, widely separated, only the distal ends visible; there 

 are no bare plates between or around them. Upper arm plates small, 

 triangular with distal margin curved, widely separated, at first wider 

 than long. Interbrachial spaces below covered like disk, only 

 the stumps are all very minute. Genital slits not conspicuous. 

 Oral shields much wider than long, rhombic with distal angle rounded. 

 Adoral plates large, rather short and wide, meeting broadly within. 

 Oral papillae three or four on a side and one at apex of jaw, long, thick 

 and sharp, subequal. First under arm plate about one-third as long 

 as second, hexagonal, wider than long; succeeding plates also hexag- 

 onal and wider than long, but the distal angle is rounded, and there 

 is a distinct median notch in the consequently convex distal margin; 

 all the plates are separated or the basal ones are barely in contact. 



a AmXooc, signifying double, equivalent to Latin duplex in reference to the two kinds 

 of spines on the disk and its close relationship to 0. duplex Koehler. 

 & Investigator, Deep Sea Oph., 1899, pi. 9, fig. 70. 



