MUSEUM OF COMPARATIVE ZOOLOGY. , 57 



OPHIACANTHA Mull. & Trosch. 

 Ophiacantha discoidea sp. nov. 



Plate XV. Figs. 406 - 407. 



Special Marks. — Seven or eight slender, translucent, nearly smooth arm- 

 spines. A small spine-like tentacle-scale. Disk densely set with minute 

 stumps crowned with thorns. 



Description of an Individual (Station 190). — Diameter of disk, 4.7 mm. 

 Arms broken ; they were plainly long, because, in their first 15 mm. there was 

 scarcely any tapering. Width of arm near disk 1 mm. Three cylindrical, 

 blunt, peg-like mouth-papillse on each side, and a similar but longer one at 

 apex of mouth-angle. Teeth longer than wide, with a rounded cutting edge. 

 Mouth-shields broader than long, regular heart-shaped, with point inwards ; 

 length to breadth, .7 . 1. Side mouth-shields very wide without, and overlap- 

 ping the first under arm-plate, but tapering to a thin point within, where they 

 scarcely meet. First under arm-plate longer than broad, and somewhat over- 

 lapped by side mouth-shields ; the plates just beyond are much wider than 

 long, of a wide axe-shape, with a broad curve without, short re-entering curves 

 on the sides, and an obtuse angle within. Side arm-jjlates meeting above and 

 below, stout and flaring, with a strong spine-crest. Upper arm-plates fan- 

 shaped, with the angle inward ; widely separated. Disk nearly round, a little 

 puffed, closely and evenly set, except in the middle, with very short micro- 

 scopic stumps crowned with 3 or 4 little thorns. No scales or radial shields ap- 

 pear in the alcoholic specimen. Seven or eight slender, pointed, translucent, 

 nearly smooth arm-spines, whereof the two uppermost are nearly as long as 

 two joints ; while those below gradually diminish in length to the lowest, 

 which is two thirds as long as a joint. One narrow, pointed tentacle-scale. 

 Color in alcohol, pale brownish gray. 



Station 190, 49 fathoms, 1 specimen. 



This species stands nearest, perhaps, to 0. cosmica, from which it is distin- 

 guished by different under arm-plates, smaller side mouth-shields, stouter disk- 

 stumps, and a very narrow spine-like tentacle-scale. 



Ophiacantha Valenciennesi sp. nov. 



Plate XV. Figs. 408-410. 



Special Marks. — Disk evenly granulated above. Seven long, slender, much 

 flattened arm-spines. Outer mouth-papilla spatula-like and covering the pore 

 of the mouth-tentacle. 



Description of an Individual (Station 192). — Diameter of disk 11 mm. 

 Length of arm 50 mm. Width of arm near disk 3 mm. Twelve mouth-papillsB 

 to each angle ; of these the outermost one on either side is wide, like a short 

 spatula, and is plainly the scale of the mouth-tentacle ; the next four papillae 



