[721]. INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 427 
The mouth-shields are long-oval, or somewhat hexagonal, narrowed 
outwardly, the outer part of the lateral edges being nearly straight, 
the onter end rounded or sub-truneate, the inner end broadly rounded. 
Side mouth-shields triangular with the three edges concave, the inner 
ends not united, the surface finely granulated. The lower arm-plates 
are separated by the side plates; the first two are longer than broad, 
pentagonal, the inner end forming an obtuse angle, the outer edge 
straight; the next two are about as wide as long, squarish, with the 
corners rounded or truncate; the following ones are broader than long, 
somewhat octagonal, the outer and inner edges longest and nearly 
straight; beyond the middle of the arm they are again pentagonal, with 
an inner angle. On the first five joints of one specimen there is only a 
single pair of tentacle-scales, which are small and rounded ; on the suc- 
ceeding joints there are generally two pairs, one of them being consid- 
erably smaller than the other; the largest specimen has two pairs of 
tentacle-scales on all the joints. 
Arm-spines three, on each side of all the joints, except the first, which 
has but two; they are thickened at base, gradually tapering, blunt at 
tip, sub-equal; the lower one a little curved downward; the upper one 
stoutest, flattened, scarcely tapering, obtuse; the middle one a little 
longer than the others, the length about equal to width of lower arm- 
plates. The upper arm-plates are transversely sub-elliptical, with the 
outer edge well rounded, the inner edge slightly prominent or angular 
in the middle, and a little concave to either side, so that the lateral por- 
tions are somewhat narrowed ; the plates generally touch each other. 
Color, when living, brown above, the central area dark brown, a 
radiating band of the same extending to each interradial margin, and 
bordered like the central area with pale gray; opposite the base of 
each arm is a squarish area or radial band of olive-brown ; radial plates 
yellowish brown, the space between them bright blue. In the center of 
the disk is a small darker brown spot, and five similar ones, correspond- 
ing to the bases of the arms, form a circle around the center; five 
others, more distant, correspond to the interradial spaces ; other more 
minute dark spots are scattered over the disk. Upper arm-plates are 
mostly dark brown, edged with pale brown or whitish; some of the 
plates are partially or wholly lighter, yellowish brown, and thus form 
transverse light bands, or mottlings, consisting of one or more plates ; 
toward the tips these light bands become more numerous, and wider ; 
spines bright brown. Lower side of disk yellowish brown, with a tinge 
of greenish ; plates around the mouth whitish ; each of the jaws with 
two brown spots; mouth-tentacles orange-yellow. Under arm-plates 
yellowish brown, with the edges paler, and with a distal median spot 
of whitish; lower arm-spines yellowish brown. In some specimens the 
arms are dull greenish above, instead of brown. 
Diameter of the disk, of the largest specimen, 11™™; length of arms, 
130", 
29 V 
