MonaxonelUda of the National Antarctic Ed'pedition. •Ill 



tion, are too liigh, and that Braun probably ^yas contented 

 with measuring a very few ova. Both find the breadth too 

 great. These observations, I may add, were conducted 

 almost entirely on specimens from Hceinatopus. 



XXXIX. — Preliminary Report on the MonaxonelUda of the 

 National Antarctic Expedition. By R. Kirkpatkick. 



The Monaxonellida brought home by the * Discovery ' in- 

 clude 43 species, of which 24 are new. Most of the specimens 

 came from the neighbourhood of the Winter Quarters (lat. 

 77° 49' S., long. 167° V 4" E.). 



Polymastia invaginata, sp. n. 



Sponge hemispherical, free or attached, covered with a 

 thick pile of pointed spicules ; with one large oscular papilla 

 usually completely invaginated, so that the sunnnit of the 

 oscule is on a level with, or below, the general surface. 

 Under surface with a fleshy basal pad. 



Colour inspirit pale yellow above, and often grey and semi- 

 transparent on the under surface in free specimens. Con- 

 sistence dense and firm. 



Skeleton. — Clioanosomal, formed of fibres curving upwards 

 from the base to the periphery, penetrating the cortex, and 

 forming the thick surface pile ; with stellate groups of small 

 tyles between the fibres. 



Cortical skeleton formed of a dense layer of vertical tyles 

 of various lengths embedded in a tough fibrous layer from 

 *5 to i"25 mm. thick. 



Basal skeleton consisting of spicules transversely arranged, 

 and crossing each other in an irregular manner. 



Spicules. — Large, smooth, slightly curved styles, or occa- 

 sionally strongyles, 2240 X 40 //-. 



Cortical tyles with small spheroidal head, short neck, 

 fusiform straight shaft, varying in length from 140 to 350 /*, 

 and in thickness from 12 to 19 yu.. A few very slender styles 

 scattered in the choanosome, 70x6/x, with head and neck 

 making an angle with the shaft. Some medium-sized cortical 

 tyles in the oscular papilla have long, oval heads. Tyles of 

 the stellate clusters slender, with the head making an angle 

 with the shatt, 200 X 15 n. 



Localities. Winter Quarters, 10-30 fath. ; off Mt. Erebus, 

 500 lath. 



