278 



BULLETIN 75;, UNITED STATES NATIONAL MUSEUM. 



(fig. 140&). Outlines of under arm plates indistinct; apparently they 

 are wider than long. Oral shields large, about as long as wide. Ado- 

 ral plates long and narrow, almost L-shaped; oral plates well devel- 

 oped. Genital slits long. Oral papilla about five on a side, most 

 proximal largest, rounded and finely serrate at tip. Teeth large, flat, 

 with rounded and serrate tips. Arm spines three, lowest slightly 

 longest equalling joint, and middle one usually shortest; each vertical 

 series of three are joined to each other by a membrane, reaching 

 nearly to their tips; in addition, all uppermost spines are joined to 

 each other by a narrow horizontal membrane, which reaches to or 

 beyond middle of spines. Color (dried from alcohol), dull purplish- 

 red, arms indistinctly banded with yellowish. 



Locality. ^Albatross station 4903, Eastern Sea, lat. 32° 31' 10'' N.; 

 long. 128° 33' 20" E., 107 to 139 fathoms, gray sand, broken shells, 

 bottom temperature 52.9° (?), 1 specimen. 



Type.— Cat. No. 25537, U.vS.N.M., from station 4903. 



This specimen is badly damaged, most of the disk being gone, but 



C 



Fig. 140.— Ophiohymen gymnodiscus. x (i- a, from above; 6, kkom uklow; c, side view of two 



ARM joints near DISK. 



its characters seem to be well shown nevertheless. Further material 

 is necessary to determine some points of structure, and observations 

 on living material can alone show what the functions of the arm 

 membranes are. It is easy to suppose they are natatorial. 



OPHIOLEPTOPLAX, new genus." 



Disk and arms covered by naked skin. Radial shields wanting. 

 Upper arm plates apparently present in form of very thin, transpar- 



o O(f)io and hnxog, signifying thin, and TrAdf, signifying -plate, in reference to the thin 

 transparent upper arm plates. 



