142 BULLETIN OF THE 



of arm 15 mm. Width of arm -witbout spines 1 mm. Seven regular, sharp, 

 conical mouth-papilloe to each angle, whereof the innermost is much the largest, 

 and resembles the teeth, which are stout, blunt, spearhead-shaped. Mouth- 

 shields small, wider than long, with a point within and a curve without. Side 

 mouth-shields wide, thick, and somewhat curved. Under arm-plates thick and 

 swollen, pentagonal, with an angle inward and outer side widest. Upper arm- 

 plates thick and swollen, short fan-shaped, with an angle inward. Side arm- 

 plates large, meeting widely above and below, swelling gradually to form the 

 spine-ridges, which are not narrow or abrupt. Disk thickly set with small, 

 slender, smooth spines (PI. X. Fig. 271), among which appear minute thorny 

 stumps and crochets. Scaling and radial shields hidden, except outer tips of 

 the latter. Seven smooth, tapering, cylindrical arm-spines near base of arm, 

 of which the two upper ones are much the longest, attaining a length of 1.7 mm. : 

 the lower ones are short and stout. At tip of arm the lowest spine is slender, 

 a little curved, and slightly rough on its edge. One small pointed tentacle- 

 scale. Color in alcohol, white. 



A young and immature specimen, but distinctly characterized by its spiny diak. 



Stati'jn 56, 1075 fathoms, 1 specimen. 



Ophiacantha Troscheli sp. nov. 



Plate IX. Figs. 223-224. 



Special Marks. — Narrow, ridge-like radial shields, which are partly naked. 

 Disk beset on radial shields and centre with short, scai'cely thorny spines, and 

 in the interbrachial spaces with grains. Arms long and sinuous. Five or six 

 stout, nearly smooth arm-spines. 



Description of an Individual (Station 33). — Diameter of disk 7 mm. Length 

 of arm 84 mm. Width of arm without spines 1.8 mm. Seven stout, short, 

 blunt-pointed mouth-papillai to each angle, of which the innermost, standing 

 under the teeth, is sometimes represented by two.' Six or seven short blunt 

 teeth. Mouth-shields small, with an angle within and a curve without ; length 

 to breadth .8 : 1.2. Side mouth-shields wide, with curved sides, extending 

 well beyond mouth-shield on either side and meeting within. Under arm- 

 plates rather thick and somewhat obscured by skin ; rudely pentagonal, with 

 an obtuse angle inward ; first plate longer than broad, irregular, compressed, 

 six-sided ; second plate also longer than broad, curved without and wider than 

 within. Upper arm-plate rather thick, yet showing the median ridge of the 

 imderlying arm-bone ; four-sided, outer side curved or Avavy, and wider than 

 inner one, lateral sides nearly straight ; length to breadth 1.2 : 1.2. Side 

 ann-plates not meeting above near base of arm, and barely touching below ; 

 projecting very slightly even near end of arm, so that the knotted or bead-like 

 outline usual in the genus is not seen. Disk set with numerous, essentially 

 smooth spines about 1 mm. long, which stand mostly in centre and on radial 

 shields ; interbrachial spaces sparsely granulated. Radial shields naked for a 



