346 BULLETIN OF THE 



70 to a square mm. In the centre of the disk they are somewhat larger ; 

 and, in the interbraehial spaces below, much more minute ; everywhere 

 they are closely imbricated and somewhat irregular in size. The entire 

 disk, above and below, is beset with a considerable number of very fmo, 

 sharp, slender spines ; the longest about .8 mm. ; just outside the mouth 

 shields is a patch of stouter and blunter spines. Arm-spines, on the joints 

 just outside the disc, twelve, arranged from the median line of the arm 

 above to the tentacle pore below. The uppermost spines are very short and 

 sharp, and project over the succeeding upper arm-plate. The sixth, seventh, 

 and eighth spines long, slender and tapering ; the four lowest spines not so 

 long, but stouter, blunt, flattened, and smallest at the base. Lengths to 

 that of the under arm-plate (Gth joint) 3., .3, .4, .4, .5, 1., 1., .8. .G, .6, .G, C, : .G. 

 On the joints within the disk, the lower spines arc wider, blunter 

 and more flattened ; while the upper ones are slender, but not so long as 

 those on the joints beyond the edge of the disk. Third joint with twelve 

 spines ; the six lower ones are arranged on the side arm-plate, nearly at 

 right angles with the length of the arm, but here the side arm-plate makes 

 a sudden bend outwards and upwards, and this part bears six slender, sharp 

 spines, of which the upper ones are somewhat the shortest ; all these last 

 are difficult of detection, wedged, as they are between the arm and the 

 lower side of the disk. Tentacle scales two to each pore. On the first 

 five or six joints the scales are shaped just like the peculiar outer mouth- 

 papilla?, and are attached to the under arm-plate near the curved margin 

 of the pore. On the joints beyond, the inner scale is pointed oval in 

 shape, and attached to the side arm-plate next the lowest spine, while the 

 outer scale is more elongated and is attached to the under arm-plate.* 

 Close to the end of the arm the inner scale only remains, and gets some- 

 what more pointed. In alcohol, grayish straw color. 



A single specimen off Sand Key, Florida, in 100 fathoms; others in 77 

 and 1G0 fathoms. 



This species, when examined with a lens, presents a confused mass of 

 thousands of spines and papilla? of all shapes and sizes; ami it is only by 

 patient study that all its parts can be properly referred. It is distinguished 

 from O. nrirabilis by its numerous arm-spines and by the different shape of 

 the outer mouth-papillae. It showed the same tendency to twist the arms 

 upwards, above the disk. 



By the kindness of Dr. Smitt and Mr. Ljungman, naturalists of the 



* It will be. noticed that the parts here called outer tentacle scales are, under 0. mira- 

 bilis, I.ym., termed arm-spines, because, in that specie-;, they are continuous with the 

 arm-spines and have the fame shape. This is done to show that arm-spines and ten- 

 tacle scales are homologous parts, and are differently named only to indicate their form 

 or position. 



