70 Proceedings of the Biological Society of Washington. 



are continued over the edges of the disk, on the lower side in each inter- 

 brachial arc covering a triangular restricted area, just as do the very 

 much shorter and much more numerous and thickly set spines in 0. 

 filogranea. 



The broad spineless areas bordering the genital slits are covered with 

 large and prominent imbricated scales as in 0. filogranea. 



The arms are approximately 33 mm. long; the upper arm plates are 

 about twice as broad as long, more or less fan-shaped, with broadly 

 rounded outer angles. The under arm plates resemble those of 0. filo- 

 granea, but are proportionately slightly longer. 



The three arm spines are rather stout basally, but taper rapidly to a 

 point; they are similar and equal in length, being roughly as long as, or 

 slightly longer than, the lateral diameter of the lower arm plates. 



On the basal portion of the arms there are two tentacle scales of which 

 the inner is much larger than the outer; further out on the arm the 

 smaller gradually decreases in size and finally disappears. On some arms 

 the smaller may be more or less completely absent even from the arm 

 bases. 



The arrangement of the plates about the mouth does not differ from 

 that found in 0. filogranea, except that the plates are somewhat more 

 swollen, the oral shields are more regularly rhombic, and the distal mouth 

 papilla? are proportionately smaller, being not greatly larger than the 

 proximal, and inwardly more separated. 



The structure of the jaws resembles closely that in some specimens of 

 0. loveni at hand from Rio de Janeiro,- but the mouth papillse are more 

 rounded and less pointed, and the distal are more separated interiorly. 



Type.— Cat. No. 34,763, U. S. N. M., from Ensenada de Santa Rosa, 

 western Cuba, in 1-3 fathoms. 



