106 BULLETIN OF THE 



separated their entire length by a broad wedge of small scales. On the under 

 surface of the disk are numerous irregular plates between the genital scales, 

 which are thick, with a wavy outline. The genital opening runs less than half- 

 way to the margin. Three very short, blunt arm-spines, situated low on the 

 outer edge of the side arm-plate. A pair of small tentacle-pores, each sur- 

 rounded by a raised burr, situated near the inner angle of the second under arm- 

 plate, on its edge ; and a similar but minute pair on the third plate. Beyond 

 this the pores are difficult to see and lie near the base of the under arm-spine. 

 The second pair of mouth-tentacles protrude from an oval rim, having on each 

 side a couple of ill-defined tentacle-scales. Color in alcohol, gray. 



The disk and arms had clinging to them small polyp-like creatures, about 

 2 mm. high, and which seemed unquestionably the Scyphostoma stage of some 

 medusa, like Cyanea. It is not easy to guess what they were doing 12,000 

 feet below the surface of the ocean. 



Station 156, 1975 fathoms, 11 specimens. 



Ophioplinthus grisea sp. nov. 



Plate II. Figs. 33, 34. 



Special Marks. — Scaling of lower interbrachial space fine (ten or twelve in 

 a transverse row). Very small, bead-like scales on first two pairs of arm-tenta- 

 cles. Two or three very minute, peg-like arm-spines, situated low down. 



Description of an Individual (Station 156). — Diameter of disk 20 mm. 

 Width of arm close to disk, without spines, 2 mm. Mouth-papilloB short, thick, 

 closely soldered together, about six on each side, with two longer blunt papilla) 

 at apex of jaw. Mouth-shields small, very broad heart-shape, with a peak 

 within, often cracked in two or more pieces. Side mouth-shitdds small, nar- 

 row, not meeting within, and so covered by the skin as to be seen with diffi- 

 culty. First under arm-plate large, three-sided, with inner angle much rounded 

 and outer edge slightly curved ; second and third pentagonal, with sharp angle 

 inward, lateral sides re-enteringly curved, outer edge slightly rounded ; those 

 beyond are rounded diamond-shape, and much broader than long. Side arm- 

 plates smooth, meeting broadly below, slightly swollen along their outer edge. 

 The basal upper arm-plates are as wide as long, of a general oval form, wider 

 without than within, and having a deep median groove. Disk covered with 

 thin, rounded, irregular plates and scales, having six large rounded primary 

 plates, one in the centre and one to each brachial space. Radial shields very 

 irregular, rudely triangular or quadrangular, with rounded corners, separated 

 their entire length by three or more rows of disk-scales ; length to breadth 3 : 3. 

 On the under surface of the disk the scales are small and very thin ; th(; genital 

 scales are long and narrow, with an irregular wavy outline and often broken in 

 three pieces. The genital opening extends less than half-way to the margin. 

 The minute blunt arm-spines, of which the under one is largest, stand low, 

 on the hide arm-plate. The second pair of mouth-tentacles issue from large 



