454 JANE STEPHENS : ATLANTIC SPONGES 



thick tufts of spicules. These fibres contain multiserially arranged oxea united by 

 spongin, which, as a rule, does not form a distinct sheath. They are 0'05-0'l mm. 

 thick, and are placed about 0'2-0'3 mm. apart in the centre of the sponge. Towards 

 the surface they are closer together, and immediately beneath the dermis they are 

 about the length of one oxea apart. They are connected by short, transverse fibres, 

 at right angles to them and running only from one main fibre to the next. The 

 transverse fibres, in which the spongin is relatively more abundant than in the 

 main fibres, and which are about 0*02-0*05 mm. in thickness, are placed much 

 closer together towards the surface of the sponge than towards its centre. They 

 contain two, three, or more rows of spicules. In places considerable numbers of 

 sand grains are present in the sponge. There is no special dermal skeleton. 



Spicules. — (l) Oxea, curved, tapering evenly to sharp points. They are short and 

 fairly thick, and do not vary much in size. They measure 0*13-0*16 mm. by 0*009- 

 0*011 mm. (2) Isochelae palmatse. — These occur in the dermal membrane and are 

 scattered through the sponge. They are 0*019-0*024 mm. in length, and they are not 

 very abundant. The whole spicule is slightly curved, and occasionally the peculiar 

 bending of the end of the axis from the inner side of the tooth can be seen, a character 

 to be found in many Homceodictya species. Usually this structure cannot be made out. 



Through the kindness of Professor Vosmaer I have been able to compare the 

 Scotia specimen with fragments of two of the original specimens from the Cape 

 of Good Hope, of which a preliminary description has been published under the 

 name Desrnacidon elastica (26). 



The arrangement of the skeleton is the same in all the specimens, and the 

 spicules are in close agreement. The oxea are similar in shape and size. In 

 Vosmaer's specimens they are 0*13-0*16 mm., with a maximum diameter of 

 0*013 mm., being, on the whole, very slightly thicker than in the Scotia specimen. 

 The palmate isochelse are similar in shape, but are slightly longer than in the 

 Scotia specimen, being 0*024-0*03 mm. in length. Sand grains and broken shafts 

 of spicules foreign to the sponge are sometimes incorporated with the skeleton. 

 In external appearance, too, the specimens are probably alike, as Professor Vosmaer 

 states that the form of his specimens resembles that of Homceodictya palmata 

 (Johnston), a species which the Scotia specimen also resembles externally. 



Homceodictya elastica differs from H. palmata in the shape of the isochelse, 

 and in the somewhat smaller size of the oxea. 



Homceodictya multiformis n. sp. (Plate XXXIX, figs. 1 a, 2, 3 ; Plate XL, fig. 16.) 



Station 482. Saldanha Bay, 5 fathoms. 20th May 1904. Three specimens. — 

 Reit's Bay, Saldanha Bay, shore. 21st May 1904. Five specimens 



Station 483. Entrance to Saldanha Bay, 25 fathoms. 21st May 1904 Thirty- 

 one large and twenty-five small specimens, and fragments 



