52 R. KIRKPATRICK. 



There are four specimens, the two larger being uniformly cylindrical and the 

 smaller ventricose. The largest is 6 cm. long, the diameter being 2 1 cm. and the 

 thickness of the wall 5 mm. 



The dermal membrane roofing over the inhalant orifices is usually supported there 

 by two or three single spicules radiating to the centre. The pores are '95 M in 

 diameter. 



Small embryos about 76 mm. in diameter occur. The new species comes nearest 

 to the species from Kergueleu, which Carter (3. p. 287) identified as Thalysias 

 subtriangularis Duch. and Mich., but which Eidley and Dendy (15. p. 9) regarded 

 as synonymous with Petrosia similis * (Ridley and Dendy). 



The spicules of the Antarctic species are very much larger than those of Carter's, 

 and partly in consequence of this the skeletal network of the latter is much denser 

 from a closer approximation of the fibres. 



The dimensions of the oxeas of four nearly related species of Petrosia are 

 as follows : 



Petrosia similis (R. and D.), 225 x 16ju. 

 Thalysias subtriangularis (D. and M.), Carter, 190 x 12 p.. 

 Petrosia (Sehmidtia) aulopora, 0. Sch., 175 x 7 p.. 

 Petrosia Jistulata, 493 x 24'4/z. 



Dredged near Winter Quarters, No. 12 hole, 25-30 fms. ; McMurdo Bay, 

 96-120 fms. 



RENIERA scoTTi.f 



(Plate XVIII., figs. 1-2, and Plate XXIV., fig. 6.) 

 1907. Reniera scotti Kirkpatrick (10a. p. 291). 



Sponge consisting of one or more fistulae. Texture very soft and easily lacerated. 

 Colour iu spirit, varying from yellow to pale reddish. Outer surface varying from 

 being finely hispid to having large couules and meandrine ridges. Inner surface of 

 fistulae very finely hispid in the spaces between the numerous orifices of exhalant 

 canals. Flagellated chambers large hemispherical, 60 x 40 p.. 



Skeleton formed of parallel longitudinal lines of main fibres, about 2-6 spicules 

 thick, curving outwards from the inner to the outer surface, where they pass into the 

 conules and ridges ; secondary fibres at right angles to the main ones, one or two 

 spicules thick. The spicules are not closely united, and spongin is only present in very 

 small amounts. 



Spicules. Oxeas 343 x 14 '6 p., curved or bent at centre, sub-tornote. 



* The specimen from Kerguelen Island which Carter identifies as Thalysias subtriangularis Duch. & Mich, 

 is, I believe, specifically distinct from Petrosia similis B. & D. The fine spicular network of the former, with its 

 slender main fibres, and still more slender unispicular secondary fibres, contrasts strongly with the thick cable- 

 like longitudinal and transverse strands of the latter. Carter's specimen appears to me to belong to a new 

 species. 



t This fine species is named in honour of Captain R. F. Scott, E.N., C.V.O., the leader of the Expedition. 



