460 JANE STEPHENS : ATLANTIC SPONGES 



wall of the oscular canal to the outer surface of the sponge, where they pierce the 

 dermis and project as tufts of spicules. These are connected by short, transverse 

 fibres which run only from one principal fibre to the next, and do not themselves 

 form continuous fibres. The two sets of fibres are at right angles to each other, so 

 that a fairly regular rectangular network is formed. The main fibres contain two or 

 three, or, for the most part, more numerous rows of spicules. The spicules are enclosed 

 in a thin, but usually distinct sheath of spongin, and the whole fibre is from 0'04- 

 0"07 mm. in thickness. The main fibres are often only the length of one spicule 

 apart, but they may be two or three, or more rarely, four spicule lengths apart, or, 

 in other words, the distance between them varies from about 0*15 mm. to 0'4 mm., 

 or more rarely to 0'5 mm. The transverse fibres contain a single spicule, or a single 

 row of spicules covered by a distinct sheath of spongin. They average about 0'03 

 mm. in thickness. There is no special dermal skeleton. 



Spicules. — Oxea, curved, tapering evenly to rather short points. They do not 

 vary much in length or thickness, being 0'14-0'17 mm. by 0"013 mm. In the 

 youngest specimen the largest oxea present measured 0'16 mm. by 0'013 mm., but, 

 for the most part, the oxea are shorter and much more slender than in the adult 

 specimens. The oxea of the embryos are about 0'065-0'll mm. in length. They 

 vary in thickness from exceedingly slender to about 0'006 mm. in diameter. 



Pachychalina hospitalis n. sp. (Plate XXXIX, fig. 7 ; Plate XL, fig. 8.) 



Station 482. Houtjes Bay, Saldanha Bay, shore. 19th May 1904. 



This species is represented by a number of specimens, most of them a good deal 

 broken, and by many smaller fragments. The shape of the specimens is rather 

 varying. Usually the surface rises up into numerous, short, finger-like branches 

 which anastomose, the whole forming a compact growth of interlacing branches 

 about 40 mm. in thickness. One specimen forms an encrustation on the inner side 

 of a large dead Patella shell, on which grow specimens of Microciona tenuis n. sp. 

 and Hymedesmia parva n. sp. Oscular tubes, up to about 7 mm. in height, rise 

 from the otherwise even surface. A similar encrusting specimen, about 9 cm. 

 in diameter, grows on a stone and spreads out over a Laminaria-like root. Other 

 specimens form fiat anastomosing branches about 5 or 6 mm. in thickness, with 

 numerous oscular tubes rising from them. The oscula are sometimes on a level 

 with the general surface of the sponge, but are usually raised above it. They are 

 about 1-3 mm. in diameter. The dermal membrane is thin. The pores are 

 scattered and are rather uniform in size. They average about 0'03 mm. Consistence 

 rather firm, but easily compressible. The surface is even, but under the lens 

 it is seen to be finely hispid, owing to the projecting ends of the main skeletal 

 fibres. The colour in spirit is pale yellow. In spite of their differences in shape, 

 all the specimens bear a general resemblance to each other. 



