MUSEUM OF COMPARATIVE ZOOLOGY. 101 



on each side. Three long, slender, cylindrical, sharp, tapering ann-spines, 

 situated close together low on the outer edge of the side arm-plates ; lengths to 

 that of an arm-joint 1.2, .8, .6 : .6. Color in alcohol, white. 



A young, with a disk of 3 mm., differed in having the upper di.sk covered 

 almost entirely by the primary and the other large plates ; the intermediate 

 disk-scales were just beginning to form. The radial shields were shorter, and 

 the papilla) above the arm fewer. 



Kerguelen Islands, 120 fathoms, 12+ specimens. Prince Edward's Island, 

 85-150 lathonis, 7 specimens (same species?). Station 152, 1260 fathoms, 

 4 specimens. 



Ophiocten umbraticum sp. nov. 



Plate V. Fiss. 131, 132. 



Special Marks. — Primary and marginal disk -plates small, and the former 

 widely separated. Arm-comb feeble. Tentacle-scales single and minute, or 

 quite wanting. 



Description of an Individual (Station 325). — Diameter of disk 9.5 mm. 

 Width of arm close to disk, without spines, 1.3 mm. Four rather wide, closely 

 joined mouth-papillaj, with one larger, diamond-shaped, at apex of the jaw. 

 Mouth-shield very thin, triangular, broader than long, with blunt angle inward 

 and corners rounded ; length to breadth 1 : 1.5. Side mouth-shields long and 

 narrow, tapering inward, where they nearly or quite meet. First under arm- 

 plate large, four-sided, the inner side being very short like a truncated angle, 

 with corners rounded ; the rest of the under arm-plates are very small, nearly 

 or quite semicircular, with a little peak inward. Side arm-plates slightly flar- 

 ing outward, meeting broadly below, where they form most of the under surface 

 of the arm ; separated above by upper arm-plates, which are four-sided, with 

 outer edge wider than inner, and curved ; lateral sides slightly re-enteringly 

 curved. Disk flat and thin, covered with small, transparent, delicate scales ; 

 si.\ small, rounded, Avidely separated primaries, one in the centre and one to each 

 brachial space ; outside these there are two similar plates in each interbrachial 

 space, one towards the centre and one near the margin ; along the margin there 

 are two irregular rows of small plates, somewhat broader than long. Radial 

 shields triangular, Avith a rounded angle inward, widely separated by the disk 

 scaling ; length to breadth 1.5 ; .8. Lower interbrachial space covered by deli- 

 cate, nearly transparent scaling, which also hides the genital scales, except their 

 outer tips, just outside the radial shields, which bear an arm-comb of three or 

 four minute papilla). Genital opening quite long, extending from the outer 

 end of side mouth-shitdds to edge of disk. There are large tentacle-pores, but 

 no scales on any of the pores. Near base of arm there are three small, delicately 

 tapering arm-spines, situated on the outer edge of the side arm-plate ; the 

 upper is about two thirds the length of an arm -joint and the lowest about half 

 as long ; farther out there are but two spines. • Color in alcohol, white. 



On the above specimen no tentacle-scales could be seen, but on others some 

 pores, at any rate, are furnished with a single minute one. 



Station 325, 2650 fathoms, 7 specimens. 



