[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 outer end rounded or sub-truncate, 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 mottliugs, 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 &quot;greenish above, instead of brown. 



Diameter of the disk, of the largest specimen, ll mm ; length of arms, 



t 



29 v 



