TETRAXONIDA. 25 



Juan Fernandez, has nearly the same spicular elements, but of different dimensions, and 

 has the labis among its microscleres. 



The specimen was dredged from 25-4 fms. due west of Balleney Island. 



HYMERRHAPHIA RUFA.* 



(Plate XXII., fig. 5, and Plate XXV' I., fig. 3a-e.) 

 Hymerrhaphia rufa Kirkputrick (10a. p. 274). 



Description. The sponge forms a thin mud-coloured brown crust on a branched 

 Polyzoon. The surface is smooth, and no pores or oscules arc visible. The consistent' 

 is rather tough. The skeleton of the choanosome is formed of longer and shorter 

 acanthostyles dressed vertically, that of the ectosome being formed of tangentially 

 arranged anisotoruotes, either isolated or in bundles. 



Spicules. Megascleres. Larger acanthostyles, 312 x 25 /u, swollen at the head, 

 spiued all over, with larger curved spines at the head. Smaller acauthostyles, 

 131 x 18 '75 /u. Anisotornotes of ectosome, 344 x 12 /u, straight, fusiform, attenuat- 

 ing gradually at one end but abruptly at the other. Microscleres. Isancorae, 28 '5 M 

 long, with three or four teeth at each end ; rarely, the teeth arc not developed, the ends 

 being in the form of hemispherical cups (XXVI. 3c). 



Dredged near "Winter Quarters, No. 10 hole, 130 fms. 



OPHLITASPONGIA NIDIFICATA. 



(Plate XXII., figs. 6, Ga, and Plate XXVI., fig. 5a-d.) 

 Ophlitaspongia nidificata Kirkpatrick (lOa. p. 274). 



Sponge massive, of an inverted pyramidal shape, sessile, narrow and contracted at 

 its point of attachment. Surface uniformly coarsely spiuous. Circular oscules (? mm. 

 in diameter) on the upper surface, at the bases of the spines. Sub-dermal cavities fiat 

 and shallow. Flagellated chambers diplodal. Colour in spirit, dirty gray, the tips of 

 the spines being yellowish. Consistence hard and tough. 



Skeleton consisting of dense branching axes of styles cemented with spongin and 

 echiuated by smooth styles passing at right angles from the axis to the surface. 

 Ectosomal spicules in form of slender straight styles. (Considerable tracts of dermal 

 membrane were devoid of these spicules.) 



Spicules. Megascleres, large, straight, smooth styles, on an average ab<>ui 

 1000 x 50 ,u. Also smooth curved kind G25 /x long. Ectosomal styles, straight, 

 smooth, tapering gradually to a point, 40G x 9 /u. Microscleres, toxa smooth, 638 M 

 long, G'25 M thick at the centre. These spicules occur in nests or groups of 5-10. 



The specimen is attached to a stone by a narrow base about 2 cm. in diameter. 

 The height is 6'5 cm., and the greatest breadth on the upper surface 7'5 cm. The 

 upper surface is triangular, each angle being slightly produced and provided with an 

 oscule, there being also an oscule in the centre. 



The spines, which are simply the ends of skeletal fibres, are about 1 cm. in height. 



* Inadvertently the specific name has been badly chosen, the colour in alcohol being that of pale brown mud. 



2 D 2 



