SPONGES FEOM THE WESTEEN" COAST OF NORTH AMEEICA. 121 



the difficulty of obtaining a good end view, the numl)er of the teeth has not been ascer- 

 tained with a great degree of certainty (Plate III., tigs. 2c, "2d). 

 Localities. — Kyska Island and Nagai Island. 



Myxilla Barentsi, Vosmaer. 

 (Plate II., figs. 9, 9a— c.) 



Myxilla barentsi, Vosmaer. 18S5. The sponges of the " William Barents" Expedition, 1880 and 1881, p. 27, pi. iv., 

 figs. 15, 16 ; pi. v., figs. 56-59. 



A few specimens referable to this species were collected at various localities. 



The measurements of the spicules taken from different specimens are as follows : — 



Spined styli (Plate II., tig. 9) ; varying in size from 0-163 by 0-006 mm. to 0-314 by 

 0-016 mm. 



Tornota (Plate IL, tig. 9a) with minutely spined ends ; from 0-176 to 0-229 mm. long 

 and from 0-004 to 0-008 mm. thick. 



Isochelœ (Plate II., fig. 9b) ; average length, 0-045 nmi. 



Sigmata (Plate IL, fig. 9c), simple and contort; average length 0-022 mm. 



Distribution. — Arctic Ocean, Behring Sea and North Pacific Ocean as far south as 



Vancouver Island. 



Myxilla parasitica, Lambe. 



Myxilla parasitica, Lambe. 1893. Trans. Royal Soc. Canada, vol. xi., p. 31, pi. ii.,^gs, 8, 8a— f. 



Two specimens of this species, both incrusting shells of Pecten hastatas, Sby., were col- 

 lected at Iliuliuk Harbour and Captain's Harbour, Unalaska Island. 



Myxilla Behringensis. (Sp. no v.) 

 (Plate IIL, figs. 3, 3a— f) 



Sponge (Plate III., fig. 3) massive, growing in irregular masses around algpe and other 

 foreign objects. Colour, when dry, yellowish-white or a light brown. Texture, firm. Sur- 

 face, undulating presenting a honey-comb appearance caused by the presence of polygonal 

 or circular openings which cover nearly the entire surface of the sponge. These openings 

 are seen to be of two distinct sizes ; the larger are distant from each other, circular and 

 generally occur in the elevated portions of the surface, the smaller are polygonal in shape 

 and are crowded together in the depressed parts of the surface. Dermal membrane, thin, 

 fragile, stretched across the openings. The larger surface openings appear to have the 

 nature of oscula and the smaller may have had pores leading into them although no evidence 

 of them has been observed in the membrane. The large openings in some cases have a 

 diameter of 8 mm. The small ones measure on an average about 1-5 mm. across but are 

 often much smaller. 



Skeleton. — Consisting of a veiy irregular reticulation of loose strands of stylote spicules 

 which is superseded at the surface by a dense felting of tylota, making a surface layer about 

 0-13 mm. thick. The dermal membrane covering the large surface openings is strengthened 

 by tylota which converge toward the centre of the opening, but the membrane across the 

 small openings is comparatively free of spicules. 



Spicules. — (a) Meçjasclera ; of two kinds; (1) Stout, slightly curved, rather abruptly 

 but sharply pointed stjdi, (Plate IIL, figs. 3a, 3b) which are often spined at the base and 



Sec. IV., 1894. 16. 



