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



In external appearance this species at first sight closely resembles Esperella 

 mammiforviis, and as it comes from the same station one is liable to confuse the two 

 before examining them microscopically. It really bears some resemblance to a typical 

 Esperella in having heads to the megasclera. The resemblance, however, does not 

 go much further. We have seen that there is no definite skeleton fibre such as exists 

 in EsjyereUa mammiformis, although the surface is hispid. The chelate spicule also 

 difi"ers much from that of an Esperella in not being properly palmate and in having a 

 widely expanded shaft, both these features being very characteristic of Cladorhiza. 



Imbedded in the soft tissues of the sponge all around the margin, and at fairly 

 regular intervals from one another, are a number of small, round, yellow bodies (Fig. 4, a, 

 and PI. XX. fig. 9), varying in size. Possil^ly they are foreign objects, but they occur 

 in the same position in all three specimens, so this view is highly improbable. Full 

 details concerning them will be found in the Introduction. 



In the arrangement of its skeleton this sponge stands quite alone in the genus, and 

 as this is generally such a good guide it seems very doubtful whether it ought to be 

 admitted as a Cladorhiza ; but for the sake of convenience we shall retain it here for 

 the present, placing it at the end as a doubtful species. 



Only three examples were obtained, one of which represents only half of the 

 sponge, while another is damaged on the lower surface, having evidently been torn 

 from its attachment. The third specimen is, however, still attached to the stone on 

 which it grew (woodcut, Fig. 4). 



Locality. — Station 147, December 30, 1873 ; lat. 46° 16' S., long. 48° 27' E.; 

 between Prince Edward Island and Crozet Island; depth, 1600 fathoms; bottom, 

 Diatom ooze ; bottom temp»erature, 34°-2. Three specimens. 



Genus Axoniderma,^ Ridley and Dendy (Pis. XX., XXL). 



1886. Trochoderma, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 344. 

 1886. Axoniderma, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 493. 



Megasclera stylote to tylostylote. Microsclera anisocheh-e of the Cladorhiza type, 

 to which may be added sigmata. In addition to these spicules there is also present 

 another form, peculiar to the genus. These may, for the present, be classed as 

 microsclera. They are amphiasters, consisting each of a long, cylindrical shaft with five 

 equal teeth arranged in a star at each end (PI. XXI. fig. 9). 



This genus is probably descended from a " Crinorhiza " form of a Cladorhiza, which, 

 as a protection against parasites and other enemies, has acquired an additional kind of 



1 From Greek a.iu«, a wheel, and lipfj.a., the skin. We are indebted to Professor F. J. Bell for pointing out to 

 us that the name Trochoderma was already in use for a genus of Echinodemis, so we have altered the name while 

 endeavouring to retain the meaning. 



