TKTRAXONIDA. 19 



The rhoanosomal skeleton is formed of fibres radiating upwards from the base -to 

 the periphery, and spreading out in the upper third of their course ; they do not pene- 

 trate the cortex. 



Spicules. Choanosomal tyles of the radiating fibres, 1120 x 20 /t, straight, 

 fusiform, attenuating gradually to a sharp point; head long, oval. 20 /t long, 17 fi 

 broad. 



Tyles scattered between the radial fibre*, varying in length from 370 to GOO/x, 

 slightly curved. 



Rgotyli'.H in form ol ^plicrotyfos, 760 ji l"H-j -ni'l i" /< m diameter al th< broad 

 distal end, which is clavate, ami with a granulated surface ; the heads at the proximal 

 end (in the interior of the sponge) are 15 /i in diameter. 



The cortical tyles (XIII. 11), 218 x 12'5/*, are slender, tapering, curved, and 

 with small oval heads and a thin neck ; there is a shorter, straight* r variety of cortical 

 tyle (XIII. 12, 12a) with a relatively thicker neck, and abruptly pointed. 



Although there is some uncertainty as to the actual size of the spicules in the 

 specimen described by Vosmaer, yet the relative proportions and characters of these 

 spicules are very similar in the Arctic and Antarctic specimens. The Arctic specimen 

 was globular and 2 cm. in diameter. 



Topsent mentions ftadiellti (tchcenus Sollas, as a synonym of Vosmaer's species. 

 Sollas gives the only names without generic or specific definition. 



The specimen was obtained from Winter Quarters, off Flagon Point, 10-20 fms. 

 It has also been found at Lat 72 14' 8" N., Long. 22 30' 9" E., 165 fms., Vosmaer, 

 Willem Barents Expedition. 



FAMILY SCBERITIDAE, Schmidt 



SUBERITES MICROSTOMU8 Var. stellatUS. 



(Plate XV., figs. 8-13.) 



Subtrittt mifrotloiiiujs Ridley and Dcndy (15. p. 199). 



There are four small specimens in the form of smooth, pale-coloured, whitish 

 rounded masses, smooth to the eye but slightly rough to the touch, encrusting the 

 stems of branching Polyzoa ; the largest is about 4*5 cm. long and 2*5 cm. broad, and 

 forms a nodulated mass on the branch of the Polyzoon. 



There are two or three minute conical pointed oscular papillae alxnit 1 mm. high. 

 The pores occur in stellate areas among the cortical tyles which occupy the rest of 

 the surface. The skeleton is composed of radiating fibres and of a dense cortical layer 

 of vertical or oblique tyles. 



Spicules. Megascleres. Large straight fusiform tyles with an oval head, 

 gradually attenuating to a sharp point, 1130 x 24 /x. The head (XV. 9a) is usually 

 sub-tylote or even stylote, and has a sub-terminal oval swelling 13/t in diameter. The 

 cortical tyles vary considerably, the figures showing three kinds. The largest 500 x 30 ft 



