TETRAXOXIDA. 41 



JOYEUXIA BELLI.* 



(Plate XVI., Figs. l-5a.) 

 1H07. Joyeuxia belli Kirkpatrick (10a. p. 283). 



Sponge attached, ovoid, with a thick firm rind enclosing a soft pulp. With short 

 conical oscular, and long trumpet-shaped poral papillae. Surface finely pilose. Colour 

 of surface yellow, of the rind whitish, and of the pith deep yellow. 



Flagellated chambers '23 X 20 /u, ; diplodal. 



Skeleton. Cortical skeleton formed of layers of strougyles crossing each other 

 at right angles. The walls of the oscular and poral papillae supported by a layer 

 of longitudinal strongyles. The surface of the sponge hirsute, with a fine pile of 

 strongyles standing out at right angles or obliquely. Choanosome without spicules. 



Spicules. Slightly flexuous smooth strongyles 850 p. long, 10 p iu diameter at 

 the ends, and 13 p in diameter at the centre. 



There is one adult specimen 5 cm. long, 3 5 cm. broad and 3 cm. thick, with 

 a deep groove on the under aspect, by which it was probably attached to a worm tube 

 or stem of a Hydroid. There is also a small conical specimen 6 mm. high, attached to 

 a piece of rock. 



I was at first disposed to regard this remarkable species as a member of a new genus, 

 partly on account of its very thick rind, which is in places over a millimetre in thickness, 

 and partly because of the highly specialised poral papillae ; but apart from these characters, 

 the new form evidently shows the closest affinities to Joyeuxia. The three hitherto 

 described species all have a rind enclosing a soft pulp, the latter being without or almost 

 without a skeleton ; then too the pulp is highly coloured. Joyeuxia tubulosa Topsent 

 and /. ascidioides (Fristedt) have fistulae, which, however, appear to be oscular. Two 

 of the species, .7. virldis and J. tubulosa. have strougyles; J. ascidioides has tyles and 

 also cheles. Accordingly Topsent places the genus near Desmacidon. 



The poral papillae attain a height of 1 to 1 "2 cm. ; they are expanded at the end, 

 the margin being sharp, usually a little jagged, and showing the ends of strougyles. 

 The mouth is closed by a sieve-like funnel-shaped membranous pore-area, which is 

 supported on its under surface by strands of tissue passing from the wall of the tube to 

 the poral membrane. 



The tube passes through the thick cortex into the choanosome, where it expands 

 before branching into four or five inhalant canals. 



Between certain parts of the inner surface of the cortex and the choanosome is 

 what appears to be a space (see XVI. 2) ; but in other parts the choanosome abuts on 

 to the cortex ; probably these peripheral spaces do not result from contraction of the 

 tissues, but form part of the exhalant canal system. 



* Named in honour of Emeritus Professor F. J. Bell, of the Zoological Department of the Natural History 

 Museum, and editor of the " Reports on the Natural History Collections " brought home l>v the ' Discovery ' 



from the Antarctic. 



2 K 'J 



