OPHIACTIS MLLLEIU. 



109 



mediate in lengtii ; lengths to tliat of under ann-plate (nintli joint), 

 ,0, .8, .'J, 1.4, .S. .(') : .1) ; neai- tip of arm, only four spines, which are 

 nearly e(iual. 'rentacle-scale stout, nearly round, rather large; length 

 to that of under arni-i)late, .:> : .('». (.'olor. in alcohol : li<<ht irrav. 



0. KrUijcri is easily distinguished hy the shape of its upper and 

 under ann-j)lates, and by its six smooth spines,, of whieh the fourth is 



much the longest 



LIST OF SPECIMENS 



Cataloffue Origitiiil Number 

 Number. Number, of Spec. ! 



Locality. 



When 

 Collected. 



Whence obtained. 



Nature of 

 S|H-ciiuen. 



436 



1024 



JfKsexin of Comparative Zoology. 

 Callao. I I Janlin dcs Plantes. | Alc-oliolic. 



Smithsonian Institution. 



1 I Callao. 



University ^luseum, 

 Copenhagen. 



Alcoholic. 



Ophiactis Miilleri Lutken. 



Ophiactis Miilkri Lutkf.x. Additamonta ad HL^t. Oph., p. 127. 



Special Marks. — One mouth-papilla, usually six arms ; upper arm- 

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



Description of a Specimen. — Diameter of disk, 3.3""" ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 1.5°"°- ; width 

 of ami 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 : .0. Mouth-papilla?, 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 papilla?. Mouth-shields a little variable, usually broad diamond-shape, 

 with angles more or less rounded ; length to ])readth, .3 : .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 thev become more ang-ular, and are 

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



