TUNICATA. 7 
HALOCYNTHITD. 
HALOCYNTHIA SETOSA. 
(Plate IT.) 
Halocynthia setosa, Sluiter, Bull. Mus. Nat. Hist. Paris, xi. (1905), p. 473. 
Localities.—(1) Winter Quarters, 10 fathoms, 19. iii. 02, one specimen, 8 x 4 x 6 cm. ; 
(2) East End of Barrier, 100 fathoms, 29. i. 02, bottom mud, stones and rocks, two 
specimens, 10 x 6 x 5 and 5 x 8 x 2°5 em.; (8) Winter Quarters, D net, No. 12 
Hole, 100 yards 8. of Hut Point, 20. viii. 03, one specimen, 9 x 5 x 5 cm.; 
(4) Winter Quarters, 20 fathoms, net, one specimen, 6 x 3°5 x 4 cm. 
External Appearance.—The body is ellipsoidal, with the longer axis dorso-ventral 
and the height about equal to the breadth. It is attached by a small bare area which 
occupies the middle half of the lower surface, and in the first specimen recorded above 
measures 4°5 x 3.cm. Colour yellowish grey, and due to the numerous long echinated 
spines that cover the test densely (Plate IL. fig. 1). Branchial and atrial apertures 
4-lobed and very far apart—5 cm. apart in a specimen measuring 9 cm. in greatest 
(dorso-ventral) diameter. 
Test leathery, not thick, 1 to 2 mm. over most of the body, increasing up to 
5 mm. on the base of attachment; white in section, smooth and glistening on the 
inside, covered externally with a dense and somewhat matted layer of tapering 
echinated spines (Plate II., fig. 2). The thickness of this layer varies from 5 to 
15 mm. (fig. 2), and the individual spines, though tough, are not stiff, and the 
consistency of the covering is more like coarse hair than bristles. The longest spines 
reach 17 or 18 mm. in length and about 1 mm. in greatest diameter, and bear a large 
number of small sharp-pointed spinules or recurved hooks (see figs. 2, A, B, and C). 
Fig. 2 B shows a type of spine where the spinules are softer and more projecting ; 
fig. 2 C a type where they are harder, sharper, and more recurved. Many of them are 
densely clothed with growths of diatoms and other minute organisms, and many small 
shells, fragments of Polyzoa, etc., are found entangled or attached to the spines. The 
specimens from localities (3) and (4) are almost wholly covered by the remains of a 
Hexactinellid sponge. 
Mantle thick, opaque, scarcely attached to test. Musculature consisting of (1) the 
siphonal sphincters, (2) a circularly running layer surrounding both apertures (fig. 3), 
and (3) internal radial and longitudinally running stout fibres starting beneath the 
sphincters. A fine fibrous connective tissue surrounds and unites these muscular 
layers. 
Branchial Sae with six large folds (fig. 5) on each side, the largest being that 
nearest to the dorsal lamina (fig. 4, Br. f). The internal bars are much more 
