﻿OPHIACTIS MiJLLERI. 



109 



mediate in length ; lengths to tliat of under arm-plate (ninth joint), 

 .5, .8, .0, 1.4, .8, .6 : .6 ; near tip of arm, only four spines, which are 

 nearly equal. Tentacle-scale stout, nearly round, rather large ; length 

 to that of under arm-plate, .3 : .6. Color, in alcohol : light gray. 



0. Krdyeri is easily distinguished by the shape of its upper and 

 under arm-plates, and by its six smooth spines,, of which the fourth is 

 much the longest. 



LIST OF SPECIMENS. 



Whence obtained. 



Spoci. 



Museum of Comparative Zoology. 



43G I . . I . . I Callao. | | JarJin des Plantes. | Alcoholic. 



Smithsonian Institution. 



1024 I . . I 1 I Callao. I I University ^luseum, | 



Copenhagen. Alcoholic. 



Ophiactis Miilleri Lutken. 



Ophiactis Miilleri Lutken. Additamenta ad Hist. Oph., p. 127. 



SjJecial Marhs. — One mouth-papilla, usually six arms ; upper arm- 

 plates regular oval ; near the edge of the disk a few spines. 



Descr'q)Uon of a Sjjecimen. — Diameter of disk, 3.. 3""°- ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, l.S""'; width 

 of arm without spines, .8""°' ; length of arm, 17"™ ; distance from outer 

 side of mouth-shield to inner points of teeth, to that between outer cor- 

 ners of mouth-slits, .7 : .6. Mouth-papillaj, one on each side, placed near 

 outer corner of mouth-slit ; thin, flat, rounded. Teeth four, longer than 

 broad, crowded ; cutting edge wavy ; lowest tooth smallest ; between it 

 and the lower end of the jaw there is a vacant space, without any teeth 

 or papilliB. Mouth-shields a little variable, usually broad diamond-shape, 

 with angles more or less rounded ; length to breadth, .8 : .3. Side 

 mouth-shields more than half as large as mouth-shields, stout, rather 

 broad ; not meeting within, but sometimes touching their next neigh- 

 bors at the outer end of mouth-slit. Under arm-plates, near base of 

 arm, short, rounded, heart-shape, with a more or less distinct angle 

 inward ; farther out on the arm they become more angular, and are 

 bounded within by a distinct angle, without by an outer side and two 



