NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 147 



plates more tetragonal, rather wider than long in the type, but in 

 some specimens (fig. 5Se) longer than wide, in contact throughout. 

 Side arm plates high, but narrow, part icularly near base of arm, where 

 they are well, separated by patches of naked skin; each plate carries 

 six or seven (rarely only five) slender, more or less flattened, sharp 

 spines, of which the lowest is the longest, a little exceeding the joint. 

 Tentacle pores large, each with two rather small tentacle scales. 

 Color (dried from alcohol), bare skin, deep brown; scales, grayish; 

 arms, yellowish. 



Localities. Albatross station 3132, off California, lat. 36 44' N. ; 

 long. 121 51' W., 33 fathoms, brown mud, bottom temperature 52.1, 

 26 specimens; station 3695, off Tsuragi Saki, Honshu Island, Japan, 

 110 to 259 fathoms, green mud, fine sand, 4 specimens; station 4965, 

 off eastern Japan, lat. 33 35' 20" N.; long. 135 10' 50" E., 191 

 fathoms, dark green-gra} 7 " sand, shells, bottom temperature 49.4, 2 

 specimens; station 4987, Sea of Japan, lat. 43 19' 20" N.; long. 

 140 17' E., 59 fathoms, rocky, bottom temperature 44.8, 2 speci- 

 mens; station 5036, south of the Hokkaido, lat. 41 58' N. ; long. 142 

 30' 30" E., 464 fathoms, brown mud, bottom temperature 37.9, 

 2 specimens; station 5039, south of the Hokkaido, lat. 42 11' N.; 

 long. 141 57' E., 269 to 326 fathoms, green mud, bottom tem- 

 perature 37.9, 8 specimens; station 5043, south of the Hokkaido, lat. 

 42 10' 20" N. ; long. 142 15' 20" E., 309 to 330 fathoms, brown mud, 

 fine black sand, coral, sand, bottom temperature 37.9, 9 specimens; 

 Monterey Harbor, Cal., 8 to 12 fathoms, 1 specimen. Bathymetrical 

 range, 33 to 464 fathoms. Temperature range, 52. 1 to 37.9. Fifty- 

 four specimens. 



Type. Cat. No. 25623, U.S.N.M., from station 3132. 



These specimens vary in disk diameter from 5 to 16 mm. In the 

 smallest, the disk is covered with minute scales except close to the 

 interradial margins, while in the largest there is no scaling on the 

 disk except very close to the radial shields. In specimens of all 

 sizes (except one large one), there are six or seven arm spines. 

 The diversity in the amount of scaling on the disk and interbrachial 

 spaces below is most remarkable, affording an unusually interesting 

 case of resorption of calcareous matter. Scales seem to be present in 

 young specimens and in regenerating disks, but their presence is not 

 wholly a matter of youthfulness, for there is some individual variation 

 in the matter. The condition of the disk in the type-specimen re- 

 minds one strongly of OpkionepJiihys, but the oral papillae are quite 

 different from those of that genus. In all particulars, except the 

 naked disk of many large specimens, acrystata is so evidently an 

 AmpJiiura, it has not seemed to me either practicable or desirable to 

 remove it from that genus. There seem to be no characters by which 

 the specimens from station 3132 can be distinguished from the 



