TUNIC AT A. 



HALOCYNTHIID.E. 



HALOCYNTHIA SETOSA. 



(Plate II.) 

 Halocynthia setosa, Sluiter, Bull. Mus. Nat. Hist. Paris, xi. (1905), p. 473. 



Localities. (1) Winter Quarters, 10 fathoms, 19. iii. 02, one specimen, 8x4x6 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 3 x 2'5 cm. ; (3) Winter Quarters, D net, No. 12 

 Hole, 100 yards S. of Hut Point, 20. viii. 03, one specimen, 9x5x5 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 II., fig. l). 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 (l) 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 Sac with six large folds (fig. 5) on each side, the largest being that 

 nearest to the dorsal lamina (fig. 4, Br. /). The internal bars arc much more 



