448 bulletin: museum of comparative zoology. 



specimen was the only one known and it seemed probable that it 

 was merely an individual variant of the widel^^ distributed and 

 variable 0. irrorata. The Albatross specimens have convinced me 

 that I was wrong and that 0. undulata is a good species. The coarser 

 disk-scaling and the stout arm-spines are very characteristic. Ly- 

 man's figures are excellent, but in the specimens before me the disk- 

 scales are more regularly arranged than in his type. The large plates 

 are surrounded by smaller ones in a somewhat ornate pattern. In 

 one specimen, the primary plates are very distinct. In these indi- 

 viduals the disk is 14 mm. across, so they are somewhat larger than 

 the Challenger specimen. 



Station 3689. Paumotu Islands: Marokau, 4 miles west of north- 

 west point. 807 fms. Bott. temp. 37.6°. Co. s., mang. 



Two specimens. 



/ 



Ophiomusium canaliculatum/ sp. nov. 

 Plate 5, fig. 5-8. 



Disk, somewhat highly arched, 8 mm. in diameter, rather more 

 than 2 mm. high; arms all broken, slender, apparently about 25 mm. 

 long. Disk covered by the six primar3^ plates, the large radial shields 

 and two additional plates in each interradius, the lower one of. these 

 two forming the margin of the disk; three very small plates occur 

 in interstices between large plates. Radial shields moderately 

 large, larger than any of the primary plates, in contact with each 

 other for almost their full length. All the disk-plates are shagreened. 

 Upper arm -plates none, unless a minute triangular plate between the 

 distal ends of the radial shields be construed as such. Interbrachial 

 areas below covered by 2 (in one interradius 3) plates, in addition to 

 the wide but very short marginal plate. Oral shields diamond- 

 shaped, somewhat wider than long; in the interradius with 3 plates 

 in the interbrachial larea the distal angle of the oral shield is truncate, 

 causing the shield to become pentagonal. Adoral plates well devel- 

 oped but not large, about 2.5 times as long as wide. Oral plates 

 somewhat shorter and a little wider. Oral papillae very indistinct, 

 apparently six or seven, but all fused into a narrow marginal piece 

 along the oral slits. First under arm-plate minute and indistinct, 

 apparently longer than wide; second under arm-plate, slightly 



•■ Canaliculatus = grooved, in reference to the deep median, longitudinal furrows on f.he arms. 



