MUSEUM OF COMPARATIVE ZOOLOGY. 161 



OPHIOGERON * gen. nov. 



Disk covered by a naked skin. Mouth-angles naked, except a few small 

 teeth on jaw-])late. 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 VII. rigs. 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 14 mm. Width of same close to disk, without .spines, 

 1 mm. 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 imder arm-plate narrow, five-sided, with inner 

 edge straight, a broad angle without, and re-entering cur^'es 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. 



* 6<pis, snake ; y^puv, an old man. 



