NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 237 



most papilla (perhaps more properly the tentacle scale of the outer 

 oral tentacle) very long, slender, spiniform, and acute; the other two 

 are similar but shorter. First under arm plate very large, hexagonal, 

 a little broader than long; second plate larger, pentagonal,- much 

 broader than long; third plate smaller than second but similar; 

 succeeding plates similar but much smaller and tending to become 

 squarish; all the plates are widely separated. Side arm plates very 

 large, all but first two or three pairs much longer than high, meeting 

 broadly both above and below; each plate carries three arm spines, 

 of which the uppermost is smooth, acute, and equals the joint, while 

 the lower two are shorter and rough at the tip. Tentacle pores large; 

 tentacle scale single, small, 

 spiniform. Color (dried 

 from alcohol), dirty- 

 whitish. 



Locality. — Albatross sta- 

 tion 4775, Bering Sea, lat. 

 54° 33' 30" N.; long. 178° 

 44' E., 584 fathoms, green 

 mud, black specks, foram- 

 inifera, bottom tempera- 

 ture 37.2°, 1 specimen. 



Type.— Cat. No. 25739, 

 U.S.N.M., from station 

 4775. 



Although there is every 

 indication that this speci- 

 men is very young (except 

 the size of the genital 

 slits), it reveals certain 

 characters that are so dis- 

 tinctive it seems best to 

 give it a name. The 

 mouth parts and the un- 

 usually long (for this family) side arm plates are quite remarkable 

 and will make the species easy to recognize. 



OPHIACANTHA MEGATRETA, new species.a 



Disk wanting, but jutlging from the scars on bases of arms, it was 

 about 25 mm. in diameter; arms about 115 mm. long, beyond disk 

 scars. Upper arm plates more or less rhombic, ^\^th rounded angles, 



a Meyac, signifying big, and rpTjzSf, signifying pierced through; that is, with big holes, 

 in reference to the conspicuous tentacle pores. 



Fig. 112.— OPHIACANTHA macrarthra. X'2o. «,fromahove; 

 6, FROM below; c, .side view of two arm joint.snear disk. 



