NO. 1989. ASCIDIAN8 FROM NORTHEASTERN PACIFIC— RITTER. 493 



I regret not being able to determine more exactly the relations and 

 orientation of the visceral mass, especially with reference to the 

 branchial sac; but in ascidians so soft as this and indeed in most of 

 the deep-water species, more or less derangement of the parts in 

 preserved specimens seems almost inevitable. 



The question of the dorsal tubercle is also puzzling. On the evi- 

 dence of a single specimen not in the best state of preservation I 

 would not venture to declare it to be entirely wanting, but although 

 the area where it should be is intact, I am unable to discover the 

 organ. 



Type-locality.— K single specimen. Albatross 3326, lat. 53° 40' 25" N. ; 

 long. 167° 41' 40" W. Beruig Sea, 576 fathoms, muddy bottom, August 

 20, 1890. Tliis location is a httle north of Unalaska, where the bottom 

 drops off quite abruptly to a considerable depth. 



Type.— Cat. No. 5683, U.S.N.M. 



AGNESIA BERINGIA, new species. 

 Plate 36, figs. 37-41. 



Superficial characteristics. — Varying from elongate-laterally com- 

 pressed to short-elli}5tical compressed, and from a soft and clean 

 surface layer to one moderately firm with much adhering and embed- 

 ded sand. Test proper colorless and semitransparent, but often 

 entirely hidden by the coating of coarse, black sand. A long slender 

 peduncle frequently, though not always, present. Siphons hardly visi- 

 ble. Largest individuals 3.7 cm. in greatest diameter, most of the lots 

 considerably smaller. Mantle thin and delicate, its musculature being 

 but little developed, and confined to the anterior end of the body; 

 a series of distinctly separated nearly parallel muscle fibers sur- 

 rounding each orifice, and a set of distant, short fibers radiating 

 from each orifice. 



Respiratory system. — Orifices rather near together, at the anterior 

 end in the elongate individuals, the branchial being considerably in 

 advance of the atrial usually (not so in the one shown in fig. 37). 

 Ijobing of the orifices obscure, six to eight lobes being indistinctly 

 recognizable. Tentacles simple, of several sizes, disposed in several 

 rather uncertain circles. Total number 50 or more, the smallest 

 mere buds. The circlet of largest tentacles nearest, and very near 

 the peripharyngeal band, the smallest nearest the branchial orifice 

 (fig. 39 h.t.). All of the tentacles thick, particularly at base, in propor- 

 tion to their length separated from one another by liberal spaces. 

 Hypophysis a somewhat urn-shaped elliptical mass with the broader, 

 open end forward ; a peculiar prominent flap of epithelial membrane 

 on the right side of the organ (fig. 39 Jiy.). The ganglion long and 

 slender, in close contact with the hypophysis at its anterior end. 

 Dorsal languets consisting of what seem to be a series of enlarged 

 papillae of the inner surface of the branchial sac, there being one for 



