MUSEUM OF COMPARATIVE ZOOLOGY. 65 



rounded, and swollen, closely joined witli the under arm-plates. Arm-joints 

 recognizable through the skin. Arms rounded and slender, tapering very 

 gradually to the end. Disk flat and somewhat angular, not rising above 

 level of arms, covered with soft, moderately thick skin. Radial shields shorter 

 and wider than, in other species, separated their entire length, and very thin 

 and flat ; from the outside they are scarcely indicated, and they do not meet 

 in the centre. Two short, stout, bluntly pointed tentacle-scales, the lower one 

 longer, and both nearly naked. Two very short genital openings, about 5 mm. 

 long, near inner angle. When the skin is removed the genital plate and scale 

 are seen, the plate being rounded, much longer than broad, tapering from with- 

 out inward, and having the small, peg-like scale attached near its outer end. 

 Color in alcohol, pale straw. 



Station 241, 2,300 fathoms, 5 specimens. 



This species, well distinguished from others, is remarkable for the great 

 depth at which it lives. The genus is usually found not far below the 100- 

 fathom line, and 500 fathoms may be considered deep for it. 



Ophiocreas oedipus sp. nov. 



Plate XYI. Figs. 443 - 446. 



Special Marks. — Arms about twenty times the diameter of disk, and slender, 

 except the base, which is swollen above, and contains the ovaries. 



Description of an Individual (Station 344). — Diameter of disk 12 mm. 

 Length of arm about 250 mm. Arm much swollen for the first four or five 

 joints next disk, where its width is 3.5 mm., then suddenly shrinking to 2 mm. 

 with a height of 2 mm. There are numerous small, flattened grains extending 

 along the sides of the mouth-angles, above the second mouth-tentacle. Eight 

 or nine broad, flat teeth, with well-rounded cutting edge, the two lowest being 

 much narrower and peg-like. On removing the skin the mouth-shield is seen 

 to be very small, a little longer than wide, with ends much rounded. Side 

 mouth-shields very large, much longer than wide, with ends much rounded. 

 Side mouth-shields very large, much longer than wide, somewhat swollen, 

 meeting within where they are narrowest. Under arm-plates composed of two 

 or more small pieces. Side arm-plates swollen, meeting below, and, at the 

 base of the arm, joined to thick, narrow, ridge-like upper arm-plates, which 

 arch upward, and nearly or quite meet on the median line. Disk angular and 

 flat, with re-entering marginal curves. Radial shields narrow and highly 

 arched, not quite meeting in the centre, covered with thin skin, which 

 under the microscope is seen to be set with fine points. Genital openings 

 large and wide, occupying the whole height of the disk. Where the skin is 

 removed the genital plate is seen to be long, very broad and thick, tapering 

 inward ; the genital scale is small and peg-like. At base of arm there is only 

 one tentacle-scale ; beyond, there are two, the upper one very small, and spini- 

 form, the lower one enclosed in a thick club-ended skin-bag. 



On opening the singular swelling on the upper side of the base of the arm, 



VOL. VI. — NO. 2. 5 



