TUNIOATA OF THE PRIBILOF ISLANDS. 529 



tliat a description of it would be justifiable, even tbougb. this must be more or less 

 incomplete. 



General character of the colony. — Apparently flat and incrusting. Specimens at 

 band closely adherent to and somewhat interwoven with laminaria roots. Quite dense 

 to the touch; a considerable quantity of sand imbedded in portions of the test; this 

 rather more abundant in the deeper parts than on the surface. Greatest dimension 

 of larg'est jjiece 3 cm., average thickness about 1 cm. Color grayish white; in portions 

 where sand is absent somewhat opalescent, so that the zooids can be seen through the 

 test with some distinctness. 



Zooids; general characters, — Probably arranged in systems, each containing but 

 comparatively few individuals; but the specimens at hand do not permit of certainty 

 on this point. Moderately numerous, rather irregularly distributed, there being con- 

 siderable areas of test which contain none at all. Placed at various angles to the sur- 

 face of the colony. Removed from the test with much difficulty. All in condition of 

 extreme contraction. Owing to this fact and the well-nigh impossibility of removing 

 them comi)lete from the test, the length of the individuals can not be determined with 

 any accuracy, but this not more than a few millimeters — 4 or 5. Thickness consider- 

 able as compared with length, even after contraction is taken into consideration. 

 Regions of the body very indistinct. Post-abdomen apparently about as long as 

 combined thorax and abdomen; broad at its origin, and tapering rapidly back to its 

 termination. 



Branchial apparatus. — Little information obtainable concerning the orifices. 

 Branchial siphon short, its 5 lobes well marked, probably in living specimens quite 

 long. Atrial siphon inconspicuous, with a wide, short languet, apparently having but 

 one lobe. Thorax very dense,owing in considerable degree to the large quantity of 

 mesenchymatous tissue and the thickness of the epithelial layer of the mantle; for in 

 spite of the extreme state of contraction the musculature is not developed to an 

 unusual extent. 



As nearly as can be determined the branchial sac contains about 10 series of 

 stigmata. 



Digestive tract. — Intestinal loop very short, indistinguishable in its several parts 

 excepting the stomach and rectum, the latter being very wide and filled with dark 

 brown faecal matter not formed into pellets. Stomach somewhat broader than long. 

 Walls longitudinally ridged on the inner surface, though the ridges are not always 

 regular and parallel. Apparently about 10 or 12 in number. 



Reproductive organs. — Ovary forming a compact mass situated some distance 

 behind the intestinal loop. Not large, so thoroughly embedded in the mesenchy- 

 matous tissue (?) — food yolk — contained in the post-abdomen that it is found with 

 difficulty. Testis not distinctly lobed, but large and massive, occupying most of the 

 post-abdomen. 



Embryos present in the atrial chamber of a few zooids. 



It is possible that careful study of more material of this species will prove there 

 are in reality two species represented here, distinguished by diiference in size of zooids, 

 form of post-abdomens, ridges in the wall of stomachs, and perhaps in some other par- 

 ticulars. But with the small number of specimens now available for examination it 

 is impossible to differentiate two such species with any satisfaction. 

 5947— PT 3 34 



