CLARK: BRITTLE-STARS. 299 



g Radial shields moderate or small; arm-spines each with a 



dusky spot on dorsal side lymani 



g' Radial shields long and narrow; arm-spines unspotted 



dyscrita 

 c' 2 (exceptionally 3) oral papillae on each side of each jaw. 

 d Upper arm-plates broadly triangular, wider than long. 



e Disk-scaling coarse; in each interradial area are about 5 series, 

 the middle one made up of the largest scales but the lateral ones 

 rather coarse; radial shields usually twice as long as broad 



abyssicola 

 e' Disk-scaling finer with about 7 series in each interbrachial area; 



radial shields |-f as broad as long canotia 



d' Upper arm-plates oval, as long as wide, or longer, basally in contact 



but distaUy quite separated from each other loricata 



a' Upper arm-plates transversely ellipsoidal, or less commonly tetragonal; 

 width 1.3-4 X length; broadly in contact with each other throughout. 

 b Disk covered in the young with rather coarse scaling both above and 

 below, but after it is 3-4 mm. in diameter the scales tend to be obscured 

 by skin, except around radial shields, and the interbrachial areas below 

 become more or less naked; spinelets usually present on disk and espe- 

 cially in interradii on margins and below; typically 2 oral papillae on 

 each side of each jaw but occasionally only 1 is present and some indi- 

 viduals have none ; upper arm-plates swollen ; a small dark spot on each 

 side of each arm-segment, either on distal margin of upper arm-plate or 

 between each pair of plates; this spot is often accompanied by a notch 

 in distal margin of upper arm-plate so these plates may have a sUghtly 

 trilobed appearance; arm-spines 5 or 6 (or more basally); color usually 



variegated green and white; cosmopcUtan savignyi 



b' Not as above. 



c 1 oral papilla on each side of each jaw. 



d Radial shields moderate or large, their length equal to half radius ^ 

 of disk, more or less. 

 e Adoral plates nearly or fully meeting interradially. 

 / Oral shields much wider than long; arms 5; arm-spines 5 or 6. 



kroyeri 

 f Oral shields not much wider than long; arms 5 or 6; arm- 

 spines 4 or 5 simplex 



e' Adorals completely separated interradially by oral shield. 

 / Disk-scales rather coarse, about 5 series in each interbrachial 

 area; oral shields pentagonal or rounded triangular, not longer 

 than wide. 

 g Arms 5-7 X disk-diameter; upper arm-plates 3-4 X as wide 



as long modesta 



g' Arms 3-4 X disk-diameter; upper arm-plates not quite 

 2 X as wide as long. 



