MUSEUM OF COMPARATIVE ZOOLOGY, 67 
r 
Three minute, evenly spaced 
1 arm-spines, Disk-scales above | 0. bullata 
8 Xi ^ tg rounded and of various sizes, Wyv. Thom. 
ETE almost with large marginal plates. 
entirely by the Three small tapering arm- 
large mouth- spines. Disk covered above 
shieldsand gen- by a rosette of large angular 
ital scales. primary plates, radial shields, O. convexa, 
and a few large interbrachial 
plates. 
Six minute arm-spines. First 
under arm-plate broader than 
long ; those beyond longer than 0 
broad. Radial shields sepa- 
rated within by a cluster of 
large scales, 
Mouth-shield Four or five minute arm- 
and genital | spines. Under  arm-plates 
^ Disk high. Basal under arm- | scales large and | longer than broad. Radial $0. variabilis. 
plates about as long as broad. | conspicuous, | shields separated at inner ends 
Arms high and rounded, with | but not cover-4 by a single scale. 
very short spines. Side arm- | ing the central | Three or four minute, wide- 
plates not meeting below within 4 margin of tlie ly spaced arm-spines. Mouth- 
disk. Side mouth-shields small, | interbrachial| shield trefoil with a pointed O. ornata, 
and at inner point of mouth- |space. lobe inward. - 
shield. Many tentacle-scales. 
(Type of O. bullata.) 
. sculptilis. 
Three minute arm-spines, 
high up. Radial shields 
rounded, separated by one { 
scale within. One large mar- 0. Lacazet, 
ginal plate with small scales 
about it, 
Three minute arm-spines. Disk covered by | 
0 
small irregular seales, small separated radial 
Shields, and very large mouth-shields. 
Two minute arm-spines. Mouth-shield 23 
lienosa. 
foil. Under arm-plates axe-shape. Radial 
shields small and rounded. 
Four minute, blunt arm-spines. Disk-plates 
rough and lumpy, with rosette of large prima- 
ries. Under arm-plates pentagonal. 
Eleven short, pointed, close-set arm-spines. | 
0. radiata, 
0. undata, 
Mouth-shields trefoil. Under arm-plates squar- 
ish. About eight tentacle-scales to each pore 
within the disk. 
Basal under arm-plates, beyond the second, about as long as broad, squarish, | 
. lapidaria. 
and with water-pores between them. Arms high, with swollen upper arm-plates 
and very small spines. Upper disk covered in great part by a rosette of primary 
plates and by radial shields, 
Disk covered with much-swollen lumpy plates. Genital scales wide, thick, and } 
0 
0 
O. solida, 
in a single piece. Basal under arm-plates longer than wide. Papille of arm-comb rugosa. 
short, flat, close-set, and with rounded ends. 
Disk-plates high and excessively swollen, Upper arm-plates rising in a high ponderosa. 
sharp ridge. Arm-spines minute, close-set, and like little blocks. n 
Interbrachial space below covered by only one or two plates besides the genital 
scales, Upper arm-plates rudimentary oy wanting. "Tentacle-pores of arm with 
only one rounded scale, 
Disk thick, and covered with thin smooth scales. No arm-comb, nor ۴ 
along genital openings. Basal under arm-plates, beyond the second, short and 
wide. 
0. 
0. minute, 
0. inermis. 
ovoid. Radial shields and 
Disk and arm-plates thick primary,plates circular and 
$ similar, 
0. Deshayest. 
swollen, and closely soldered. 
Side mouth-shields large and | 
Mouth-papillæ and scales of T : Side mouth-shields small. y 
mouth-tentacles thick, squar- ae true arm- J Month.shield broader than pO. inornata. 
ish, irregular, and crowded, $ FMD: long, with a peak inward, 
Arm-spines minute, with tenta- Disk-plates irregular and 
cle-scales similar in form, and humpy. A group of papille 
Standing only on side arm-plate, near the arm, on margin of in- 0. confragosa, 
inside the pore. terbrachial space, 
A small arm-comb, Side mouth-shields very O. intori 
narrow, 
