SPONGES FEOM THE WESTEEN COAST OF NORTH AMERICA. 125 



Phakellia ventilabrum, Bowerbank. 1864. Mon. Brit. Spong., vol. i., p. 186; vol. ii., p. 122; vol. iii., p. 57, pi. xxii., 



figs. 1-7. 

 " " Verrill. 1873. Am. Jour. Sci. and Arts, vol. vi., p. 440 and vol. vii., p. 413. 



" " ? Whiteaves. 1874. Report on deep-sea dredging operations in the Gulf of St. Lawrence, p. 9. 



« " var. connexim, Ridley and Dendy. 1S87. Rep. Monaxonida, Zool. Chall. Exp., vol. xx., p. 170, 



pi. XXXV., figs, o, 3a. 



There are a immlier of cup-shaped specimens of this species from Alaska, the hxrgest of 

 which has a height of 250 mm., a width at the top of 170 mm. and a thickness of 13 mm. 

 half way up the stalk. The growth of this sponge, in most instances, is much more robust 

 in this region than in the Gulf of St Lawrence, although large specimens have been found 

 further south, off the coast of Maine. A few of the specimens, however, are quite small and 

 bear a strong resemblance in general appearance to the Gulf of St. Lawrence sponge. 



In spiculation a considerable variation is noticeable ; whilst in some specimens there is 

 a decided tendency toward the separation of the spicules into two sizes, the smaller spicules 

 being at the surface, in others the difference in size is less marked or not apparent at all. 

 The maximum length of the spicules in different specimens, varies from 0-353 to 0'628 mm. 

 with an average thickness of 0-013 mm. In individual specimens the variation in length of 

 the spicules is considerable. Three sponges from St. Matthew Island, Behring Sea, des- 

 cribed in the ' Transactions of the Royal Society of Canada, 1892,' as a variety of Phakellia 

 papyracea, Ridley and Dendy, are now seen to be evidently a form of Phakellia ventilabrum, 

 Johnston, in which the spicules show a marked tendency to division into two sizes, a char- 

 acter which is, as shown by other specimens in the present collection from Alaska, not a 

 permanent character. 



Distribution. — Arctic Ocean, Behring Sea and North Pacific Ocean. 



Phakellia Dalli. (Sp. nov.) 

 (Plate III., figs. 5, 5a-d.) 



Sponge (Plate III., fig. 5) erect, with a spreading root and a long, stout stem, divided 

 at a considerable height above the base into three branches which again subdivide once or 

 twice, anastomose and terminate in cup-shaped expansions ; total height of sponge 344 mm. ; 

 height of stem 205 mm. ; length of branches before subdivision 70 mm. ; diameter of stem 

 15 mm. ; diameter of main branches about 12 mm. The stem is of about the same thickness 

 throughout its length and the main branches are nearly as stout as the stem whilst the sub- 

 divisions of the branches are short and onlj' slightly reduced in thickness. The largest of 

 the cup-shaped expansions, of which there ai-e four, has a diameter of nearly 45 mm. Colour, 

 when dr}', dull ])rt)wnish-yell(iw, Texture, of stem and branches, compact, firm, unyielding, 

 of the terminal cups, moi'e open, elastic. 



Skeleton. — Separate, well defined fibres of spicules pass along the central portion of the 

 branches and of the walls of the cups ; these by subdivision and branching give rise to 

 subsidiary fibres which run to the surface. The fibi-es are connected b}' individual spicules 

 crossing them at right angles. The stem and lower portions of the branches are strength- 

 ened by the development of horny fibres covered by stylote spicules running longitudinally 

 in the stem and branches and crossed at right angles by fibres of spicules passing to the 

 surface, the whole forming a somewhat compact reticulation. The surface ends of the fibres 

 terminate in indistinct brushes. 



