MUSEUM OF COMPARATIVE ZOOLOGY. 161 
OPHIOGERON * gen. nov. 
Disk covered by,a naked skin. Mouth-angles naked, except a few small 
teeth on jaw-plate. Under arm-plates small, and with a large tentacle-pore on 
either side. Side arm-plates somewhat flaring, and carrying thorny arm-spines 
covered with skin. No upper arm-plates. 
This genus is somewhat allied with Ophiomyxa, and with Ophioscolex. 
Ophiogeron edentulus sp. nov. 
Plate VIX. Figs. 187-189. 
Special Marks. — Two or three feeble, pointed teeth ; otherwise the mouth- 
angle quite naked. Two short stout arm-spines, which, stripped of skin, show 
longitudinal rows of hooked thorns. 
Description of an Individual (Station 175). — Diameter of disk 3 mm. 
Length of arm about 14mm. Width of same close to disk, without spines, 
1mm. Mouth-angles quite naked, except one small pointed papilla at apex of 
jaw and two or three more that represent teeth. Mouth-shields rounded trian- 
gular ; length and breadth about equal, with an angle within and outer side 
rounded, Side mouth-shields rather large, curved, longer than wide, broadest 
within, where they meet. First under arm-plate narrow, five-sided, with inner 
edge straight, a broad angle without, and re-entering curves on the lateral sides, 
second plate similar, but narrower and with the angle inward. Those beyond 
are further modified by having the outer and inner sides curved. Side arm- 
plates broad and meeting below, beyond the second under arm-plate ; flaring 
somewhat toward their outer edge. The arm-plates and mouth-shields are more 
or less obscured by thick skin. Along the upper side of the arm the central 
ridge of the arm-bones shows through the skin. Disk flat and thin, completely 
covered with a naked wrinkled skin. Two short tapering arm-spines, which 
when stripped of skin present longitudinal rows of slightly hooked thorns. 
No tentacle-scales, but large pores from which long smooth tentacles protrude. 
Color in alcohol, grayish. 
Station 175, 1350 fathoms, 2 specimens. 
* dis, snake ; yépwr, an old man. 
