432 bulletin: museum of comparative zocjlogy. 



Station 4651. Ill miles northwest of Aguja Point, Peru. 2222 

 fms. Bott. temp. 35.4°. Fne. stk. gy. m. 



Station 4674. 86 miles southwest of Palominos Light House, Peru. 

 2338 fms. Fne. dk. gn. m., r. 



Eleven specimens. 



( Ophiacantha quadrispina,^ sp. nov. 



Plate 1, fig. 3, 4; Plate 2, fig. 3. 



Disk, 18 mm. in diameter; arms about 100 mm. long. Disk cov- 

 ered by a coat of fine scales which is more or less completely con- 

 cealed beneath a covering of coarse granules, 25-35 per square 

 millimeter. About one square millimeter or a little more of the distal 

 end of each radial shield is bare. Upper arm-plates wider than long, 

 separated or barely in contact, diamond-shape but with distal angle 

 much more obtuse than proximal; near tip of arm, they are nearly 

 triangular and about as long as wide. On the interbrachial areas 

 below, the granulation occupies only the central, marginal portion, 

 the region bordering the genital slits and distal to the oral shield 

 being quite bare, though covered with very fine scales. Genital 

 slits of unequal lengths, sometimes equal to Only the two basal arm- 

 segments and sometimes equal to four. Oral shields distinctly wider 

 than long; the madreporite is pentagonal with slightly concave sides, 

 and is widest proximally; the other shields are diamond-shaped with 

 rounded angles, slightly concave sides and a conspicuous distal 

 projection into the interradial area. Adoral plates nearly or quite 

 straight with almost parallel sides, about 3 times as long as wide, 

 meeting broadly in the interradii but separated radially by the first 

 under arm-plate; often, but by no means always, a distal projection 

 of the adoral plate separates the oral shield from the first under arm- 

 plate; in the 40 possible cases, this projection is present 25 times. 

 Oral plates superficially about as large as adorals; on the margin of 

 each are 3-6 papillae of very variable size and arrangement; as a 

 rule the distalmost is largest and the middle ones smallest, but the 

 distal ones may be quite lacking. Teeth five in each column; below 

 (or external to) lowest, is a group of 2-4 tooth-papillae, each about 

 equal to half a tooth. First under arm-plate, small, squarish, a little 



1 Quadrispinus = having four spines; in reference to the small number of arm-spines. 



