MUSEUM OF COMPARATIVE ZOOLOGY. llo 



arm-plates beyond the third. Four small, equally spaced arm-spines. Small 

 upper arm-plates. The great lower iuterbrachial plate has usually two much 

 smaller at its outer corners. 



Description of an Individual (Station 24). — Diameter of disk 8.5 mm. 

 Width of arm, without spines, close to disk 2 mm. Mouth-papillas five on 

 each side, with a large diamond-shaped one at angle of jaw, all forming a close 

 line. Mouth-shields large, irregularly pentagonal, with an acute angle inward 

 and outer edge straight ; length to breadth 2 : 1.7. Side mouth-shields longer 

 than broad, wider without than within ; outer ends curved, touching by their 

 narrow ends within. Genital scales large, semicircular, stretching from mouth- 

 shield to margin of disk. There are only three under arm-plates, the first 

 small and diamond-shaped, lying at outer end of mouth-slit ; second and third 

 pentagonal, with an angle inward, and lateral and outer sides nearly straight. 

 Side arm-plates thick, slightly swollen, and beyond the third under arm-jjlate 

 forming the entire covering of the arm, with the exception of rudimentary 

 triangular upper arm-plates, which do not extend to the tip of the arm. Disk 

 rather flat, and covered by closely soldered plates ; the upp6r surface is occupied 

 by six primary plates, separated by many smaller ones ; radial shields rounded 

 triangular, with acute angle within ; outer edges curved, strongly diverging 

 inward, and separated by a triangular scale. In iuterbrachial space are two 

 angular plates, the outer one wide quadrangular and closely soldered to a 

 great marginal plate, which, with the genital scales, covers the iuterbrachial 

 space on the under surface of the disk. At base of arm above are four little 

 plates, two central and two lateral. Four short, blunt, and thick arm-spines, 

 situated low on the outer edge of the side arm-plate. Tentacle-scales minute, 

 rounded, situated on the inner angle of second and third under arm-plates. 

 Color in alcohol, pale gray. 



In presence of the many new species of Ophiomusium, it has been thought 

 well to give figures and a full description of this one. 



Station 24, off St. Thomas, 390 fathoms, 2 specimens. Station 23, close to 

 Sombrero, 450 fathoms, 3 specimens. 



Ophiomusium simplex sp. nov. 



Plate I. Figs. 10, 11. 



Special Marks. — Most of the lower iuterbrachial space outside the mouth- 

 shield is occupied by broad genital scales and a great central plate. No under 

 arm-plates beyond the third. Two minute arm-spines set low down. Besides 

 the great iuterbrachial plate below there are three others along the margin. 



Description of an Individual (Aniboyna). — Diameter of disk 6 mm. Width 

 of arm without spines 1.5 mm. ; length of arm 15 mm. Mouth-papilla) seven 

 on each side, and one, spearhead-shaped, at angle of Jaw, closely soldered 

 together and forming a slightly rai.sed continuous line. Mouth-shields little 

 longer than broad, pentagonal, with acute angle within, at the corners of 



