251 



Skeleton. — Cortex formed of alternating transverse and 

 longitudinal layers of amphityles, these latter also being 

 scattered in the soft tissues. 



Spicules. Megascleres. — Amphityle, 530 x 22 /x, smooth, 

 curved ; with long oval head 28 /n long, and 14 fx broad. 



Acanthoxea (rare), 200 x 44 /.i, slightly curved, fusiform, 

 sharp-pointed, smooth at the ends, but with pyramidal spines 

 on each side of the middle line directed towards the middle. 



Microscleres. Sigma, 38 x 3.5 ^t, contort smooth. 



Isochele, tridentate, 20 /n long. 



Trichites, rarely joined into trichodragmas, 275 /d long. 



Spined coiled microsclere, 1 1 ^t by 4 /.t in total breadth ; and 

 spined cruciate form (fig. i8e). 



Locality C. — Off Tugela River mouth, Natal, 65-80 fms. ; 

 bottom, hard ground. 



There are two specimens of the new species, one attached by 

 one of its tubular processes to a worm tube, the other free. 



The free specimen is 11 /z in total length, it possesses 4 

 oscular distinct tubes and indications of 4 others ; the size of 

 the largest tube is 3 x i mm. 



This species is near Histoderma appeiuliculatnvi, Cr,, from 

 the N. Atlantic, but there are distinct specific differences. The 

 acanthoxeas and spined coils are absent in the Atlantic species, 

 and the large styles occurring in the latter are not present m the 

 Natal form ; further, the other spicules common to both species 

 vary greatly in size, as will be seen from the following table : — 



Amphityles. Isocheles. Sigmas. 



H. appcndicitlatuvi - 1085 x 20 ^ 35 yu long 132 x ^ H- 

 H. natalensc - - 530 x 22 fi 20 fj. long 38 x 35 fx. 



Dendy's supposition [6, p. 26] that Siderodenna, Ridley and 

 Dendy, is identical with Histodentia, is undoubtedly correct. 



The microscleres, which I have termed spined coils, at first 

 seemed to me to be spined spirulae, but they are possibly 

 modified sigmas. They resemble in some measure the spined 

 isocheles of Leptosia sclunidti, Topsent [19, pp. 232, 250, 

 fig. 2b]. 



Genus Dendoryx (Gray^. 

 Dendoryx incrustans (Esper). 

 1805-1830. Alcyoniiiiii incnisfans, Esper [9, Alcyoniuiu, tab. xv.]. 

 1842. Halichondria incrustans, Johnston [10, p. 122, pi. xii., lig. 3 ; and pi. xiii., 



fife'- 5]. 

 1866. Halichondria incrustans, Bowerbank [2, ii. p. 249, ni. p. 107, pi. xliv., 



tigs. 7-12]. 

 1894. Dendoryx incrustans, Topsent [17, p. 13]. 



The sponge forms an irregular incrustation round the stem 

 of a large Hydroid. The ectosomal spicules are all amphi- 



