REPORT ON THE MONAXONIDA. 171 



Norway (Schmidt) ; Arctic Ocean, off Norway (Vosmaer) ; Baltic Sea (Fristedt) ; ? Gulf 

 of St. Lawrence (Whiteaves) ; Florida, Gulf of Mexico and Barbados (Schmidt) ; off 

 Brazil and north-east of Falkland Islands (Challenger). 



The species is typically an inhabitant of deep water, being common in depths over 

 100 fathoms, seldom occurring in shallower water, and going dowai to 1035 fathoms, as 

 shown by the Challenger dredgings. 



Phakellia jiahellata, Ridley and Dendy (PI. XXXIV. figs. 2, 3, 3a; PI. XL. 

 figs. 6, 6o). 



1886. Phakellia fla J lellata, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. .5, vol xviii. p. 478. 



Sponge (PI. XXXIV. figs. 2, 3) erect, stipitate ; stem rather short, stoutish, cylindri- 

 cal, ending below in a widish, flattened base of attachment, and expanding rather suddenly 

 above into a broad, flattened, vertical lamella with undulating margin. One side of the 

 lameUa is thrown into more or less pronounced, rather irregular, longitudinal furrows and 

 ridges, while the other is comparatively smooth and bears numerous stellately disposed 

 oscula (PL XXXIV. fig. 3a). The finest specimen in the collection is 125 mm. in total 

 height and the same in breadth ; the stem is 25 mm. long and 8'5 mm. in greatest 

 diameter (being not quite round). The lamelliform portion is only about 3 mm. thick 

 (except along the prominent ridges). Colour in spirit greyish-yellow. Texture rather 

 soft and brittle. Dermal membrane thin and transparent. Pores very abundant on the 

 surface which bears no oscula, in small groups over the ends of narrow inhalent canals, 

 where they reduce the dermal membrane to a mere network ; the pores themselves are 

 round or oval openings about 0'07 to O'l mm. in diameter; on the opposite side of the 

 sponge they are scarce or absent. Oscula (PI. XXXIV. fig. 3a) numerous, on one side 

 only of the sponge, in round, stellate groups of eight or ten ; the oscula themselves 

 are minute, round and about 0'5 mm. in diameter; the groups are fairly regularly 

 placed at about equal distances, and are about 4 mm. (or a little less) in diameter. 



Skeleton. — From the point where the stem enters the sponge stout, branching bands 

 of spiculo-fibre, containing a very large proportion of dark-coloured, horny cementing 

 material, radiate upwards through the soft tissues. In addition to this fibrous skeleton 

 there is a rather irregular, somewhat Halichondrioid reticulation of stout stylote 

 spicules, terminating at the surface in divergent brushes of much smaller, slender styli. 

 Each Inrush surrounds the apex of one of the larger styli, and the apices of its own 

 spicules project for a short distance beyond the surface of the sponge. 



Spicules. — Megasclera; (l) stout, smooth, slightly curved, sharply and rather 

 abruptly pointed styli (PI. XL. fig. 6); measuring about 0"5 by 0'03 mm.; forming the 

 main skeleton, occurring both in the fibre and in the reticulation outside of it. (2) Much 

 smaller, straight, smooth, slender styli (or subtylostyli) (PI. XL. fig. 6a), sharply and 



