TETRAXONIDA. 39 



figures of the spicules that the diftereuces between the var. antarctica and var. cactoides 

 are merely those of degree ; the teeth of the isochelae, for instance, are more 

 approximated in the latter than in the former ; further, the rounding of the ends of 

 the oxeas is not an important distinction ; and lastly, the cactus-like surface would 

 result from a branching of the ends of the skeletal fibres just below the surface, so 

 that the dermal layer would stretch over the points of bifurcation. 



If the new variety were devoid of cheles it would be placed under Batzella, thus 

 justifying Thiele's observation (23. p. 438) that the latter genus might be regarded as 

 a Desmacidon which had lost its chelae. 



One specimen was dredged from Winter Quarters, No. 12 hole, 25-30 fms. 



Desmacidon spiotgera. 

 (Plate XIX., figs. 3, 3a, an<l Plate XXIIL, figs. 3a-c'.) 

 1907. Desmacidon spinigera Kirkpatrick (10a. p. 28;>). 



Sponge digitiform, or knob-like ; surface coarsely spinous. Consistence rather 

 hard. Colour pale red. Several small oscules about 2 mm. in diameter. 



Dermal membrane spread like a delicate net between the spines, and at some 

 distance from the floors of the sub-dermal spaces. 'Flagellated chambers oval, 

 4G X 32 /x. 



Skeleton formed of coarse, longitudinal, main strands, about 180 /a thick, radiating 

 out to the surface, with loose scattered spicules between, united in horizontal bundles 

 only beneath the surface. 



Spicules. Megascleres. Oxeas 731 X 26 /a, curved at centre, mostly sub-toruote, 

 though some attenuate gradually, with sharp pointed ends. 



Microscleres, of one kind, viz., isochelae palmatae, 24"64 /x. long, and 5*28 /u, broad 

 on side view ; pointed at each end ; with straight axis ; with palmate teeth 8 • 8 ju, long, 

 and with narrow alae 8 ' 8 yu, long. 



Four specimens were obtained. The type specimen (XIX. 3) from 10 hole, 

 130 fms., is digitate, 7'5 cm. in length and 2 cm. in diameter. The spines are 

 • 2- • 5 cm. long, those at the lower end pointing obliquely upwards, but above becoming 

 vertical to the long axis. Another specimen forms a spheroidal knob encrusting the 

 stem of a zoophyte. 



A third specimen is in the form of cylindrical fragments. 



A fourth specimen, much macerated, is massive and bifurcated, and about 

 12-5 cm. long ; further there is a considerable amount of .spongin present, sometimes 

 appearing as distinct fibres, where the spicules have become lost or dissolved away. 

 The spicules are in all respects identical with those of the foregoing forms. 



This species bears much resemblance to Desmacidon setifer, Topsent, obtained 

 by the ' Belgica ' from the Antarctic. The isocheles are of much the same character, 

 but those of D. setifer are very much larger, viz., 75-100 m by 18-20 m- Further, 



VOL. IV. 2 F 



