MUSEUM OF COMPARATIVE ZOOLOGY. Ill 



Widtli of arm, ^vithout spines, close to disk 2 mm. Mouth-papillae seven on 

 each side, three basal ones considerably largest ; all forming a close line. 

 Mouth-shields small, triangular, with acute angle inward, and outer edge much 

 rounded. Side mouth-shields large, much longer than broad, wider without, 

 meeting within ; length to breiulth 1.7 : 1. Under arm-plates from the second 

 to the fourth or fifth furnished with tentacles ; they are axe-shaped, with an 

 angle imvard, lateral sides re-enteringly curved and outer side curved ; beyond, 

 the plates are rudimentary and diamond-shaped. Side arm-plates thick, meet- 

 ing above and below beyond the disk. Upper arm-plates diamond-shaped, 

 with an angle without and within ; length to breadth .7 : .7. Genital scales 

 long and narrow, bearing a row of papillae on the free edge. Lower inter- 

 brachial space covered by thin curved plates, of which five form a transverse 

 row along the disk margin ; upper surface of disk pentagonal. Radial shields 

 triangular, separated their entire length by a row of small plates ; and there 

 is a similar row in each interbrachial space ; the central space within the 

 radial shields is covered by six circular primary plates separated by small 

 ones. Arm-spinos six or seven in number, very short and blunt, situated on 

 the outer edge of the side arm-plate. No scales beyond the fourth or fifth 

 under arm-plate : they are large, oval, and situated near the inner angle of the 

 plate, one to each pore. Color in alcohol, gray. 

 Station 224, 1850 fathoms, 3 specimens. 



Ophiomusium cancellatum sp. nov. 



Plate I. Figs. 17, 18. 



Special Marks. — Arms rather slender and tapering, cylindrical or but 

 slightly wavy. Upper and under arm-plates persisting nearly to end of arm, 

 but no tentacles beyond third or fourth under plate. Genital openings bounded 

 by small close-set papillae. Disk flat, covered with small imbricated scales, 

 which are nearly ef[ual, except the marginal, which are larger. Upper arm- 

 plates large ; the basal ones long hexagonal. 



Description of an Individual (Station 236). — Diameter of disk 8.5 mm. 

 Width of arm, without spines, 1.5 mm. Length of arm 28 mm. Mouth- 

 papilloe forming a close line, six on each side, with one, diamond-shaped, at 

 angle of jaw. Mouth-shields triangular, Avith an .angle inward, sides equal 

 and curved ; length to breadth 1:1. Side mouth-shields long triangular ; 

 much wider without than within, where they do not quite meet. Genital 

 scales concealed under fine, closely set disk-scales. Under arm-plates pentagonal 

 near base of arm, farther out quadrangular, with an angle inward ; one tenta- 

 cle-scale, which is round, and situated on inner angle of the second and third 

 under arm-plates. Side arm-plates thick, minutely tuberculous, meeting be- 

 low, but not above, near base of arm. Upper arm-plates near base of arm 

 hexagonal, with outer and inner sides very short. Disk covered above and 

 below by thin, rounded, minutely tuberculous scales ; on the margin are larger 



