104 THE VOYAGE OF H.M.S. CHALLENGER. 



Fibres composed entirely of spieula arranged in accordance with the axis of the filjre, 

 cemented together and thinly coated with keratode." This diagnosis is even more 

 indefinite than that of Vosmaer, which runs as follows : — " Rods smooth or spined. 

 Anchors bi- or tridentate, also palmato -dentate, equiended. ' Keratode-fibre ' very 

 conspicuous." -^ 



Under these circumstances the only thing left for us to do was to take Bowerbank's 

 type of the genus, viz., Desmacidon fruticosa, and unite with it those sponges which 

 have a similar spiculation (as given above). We are conscious of the jjossibility that 

 our diagnosis may prove to be too limited, but there can, we think, be little doubt that 

 whatever sponges fall within its limits will form a natural group, which can scarcely be 

 said of the two previous diagnoses. 



The genus, even as above restricted, has a very wide geographical range, being 

 found in British and Australian Seas and off the east coasts of North and South America, 

 and, if we include the subgenus Homceodictya, as far south as Kerguelen Island. 



Desmacidon fruticosa, Montagu, sp., var. (PI. XXIII. figs. 10, 10a, 106, 

 10c, lOc^ ; PL XXX. fig. 1). 



1818. Sporujiu fruticosa, Montagu, Mem. Wern. Soc. EcLin.,vo). ii. p. 112, pL xiv. figs. 3, 4. 



1842. Haliehondria fruticosa, Johnston, British. Sponges, p. 103. 



1864. Desmacidon fruticosa, Bowerbank, Mon. Brit. Spong., vol. L p. 200. 



AVith this species we unite, as a variety, an interesting specimen from the south-east 

 of Australia. The sponge (PI. XXX. fig. 1) arises from a short, stout peduncle, and 

 expands into a broad, somewhat compressed palm ; its height is about 62 mm. It agrees 

 with Bowerbank's specimens in having a distinct fibre, and, still more closely, in spicu- 

 lation. The spicules are oxea (PI. XXIII. figs. 10, 10a, lOcZ), tridentate isochelae 

 (PL XXIII. figs. 106, 10c), and sigmata. The oxeote is of about the same size 

 (about 0'25 mm. long) in both, but in the Challenger variety is jjerhaps not quite 

 so abruptly pointed and without any marked inequality of the two ends such as is 

 often visible in Bowerbank's specimens. In the Challenger variety, again, the chelae 

 are slightly larger and of stouter build than in the British form (measuring about 0"038 

 as against 0"0315 mm.), and the sigmata also appear to attain a slightly greater size 

 (reaching up to about 0'063 mm. in length). 



The surface of the sponge is scored with a few deep, broad, longitudinal grooves or 

 channels (PL XXX. fig. 1), mostly confined to one side. It is doubtful whether these 

 grooves are natural or whether they have been caused by the sponge growing up against 

 some cylindrical, branching organism. 



Localitij. — Station 163a, April 4, 1874; lat. 36° 59' S., long. 150° 20' E.; off the 

 south-east coast of Australia ; dejDth, 120 fathoms ; bottom, green mud. One specimen. 



1 Notes from the Leyden Museum, vol. ii., 1880, p. 130 ; see also Porifera, in Bronn's Klass. u. Ordnung. des 

 Tliierreichs, p. 350. 



