210 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



even octagonal; distal angles often rounded instead of truncate; all 

 of the under arm plates are near together, but they may be slightly 

 separated; they are often in contact. Side arm plates moderate, not 

 meeting above and only slightly, if at all, below; each plate carries 

 seven or eight smooth, stout but delicate arm spines, which are more 

 or less distinctly flattened; the spines are not only hollow, but the 

 central cavity is relatively very large; uppermost spine (or one next 

 to it), longest, rather exceeding two joints; basal series of spines of 

 opposite sides not noticeably approximate. Tentacle scales two on 

 each pore, long, flat, and blunt ; in large specimens the basal pores have 

 three scales. Color (dried from alcohol), disk, brown of some shade, 



FIG. 97. OPHIACANTHA DIPLASIA. 



X 2.25. a, FROM ABOVE; b, FROM BELOW; c, SIDE VIEW OF TWO ARM 



JOINTS NEAR DISK. 



ranging from very light to very dark; arm spines usually much lighter 

 than disk and often nearly white; occasionally the disk is dark brown, 

 mottled with a lighter shade. 



Localities. Albatross station 3051, off Oregon, lat. 43 59' 19" N.; 

 long. 124 58' 30" W., 59 fathoms, coral, broken shells, rocky, 23 

 specimens; station 3053, off Oregon, lat. 44 4' 30" N.; long. 124 50' 

 W., 64 fathoms, coral, broken shells, rocky, bottom temperature 

 47.3, 5 specimens; station 3054, off Oregon, lat. 44 13' N. ; long. 

 124 44' 30" W., 53 fathoms, rocks, bottom temperature 48, 3 speci- 

 mens; station 3078, off Oregon, lat. 43 59' 15" N. ; long. 124 46' W., 



