SPONGES — WHITELEGGE. 457 



2 to 10 mm. apart, with an indistinct concentric arrangement of 

 the valleys between the ridges. The spicules are slightly curved 

 oxea 0-06 to 007 by 0-004 mm. 



This form, like many other species of the genus, is subject to 

 great variation, and no doubt if a large series were secured it 

 would be impossible to say where a definite line could be drawn, 

 so as to warrant even a varietal name. 



PACHYCHALINA AUSTRALIS, Lendenfeld, sp. 



Euplacella australis, Lendenfeld, Zool. Jahrb., ii., 1887, p. 789 



Buplacella fr'ondosa, Lendenfeld, Zool. Jahrb., ii., 1887, p. 789, 

 pi. xxi., fig. 36. 



Stations 44, 47, 48. 



When writing the " Report on Sponges from the Coastal 

 Beaches of N. S. Wales "^' I gave a short description of this 

 species. The " Thetis " collection contains seven fine examples. 

 They are all more or less stipitate, and vary from flabellate to 

 plate or narrow cup-shape. The outer surface is smooth, and 

 exhibits numerous growth lines, the pores are very minute and 

 cannot be seen clearly with the unaided eye. The inner surface 

 is closely sprinkled with abundant oscula from 05 to 2mm. in 

 diameter, and from 1 to 5 mm. or more apart. In young examples 

 the oscula are large and rather distant. A few scattered oscula 

 are invariably present on the external surface of the pedicle. 

 The dermal reticulation on the outer surface is much finer than 

 that on the inner. The skeleton consists of a rather dense plexus 

 of broad ill-defined fibres, the mesh varies considerably, but is 

 usually more or less oblong. The horny matter of the fibres is 

 well developed and furnished with abundant oxeote spicules, 

 especially in the central region ; at the surface, however, the 

 horny matter is scanty, and the spicules are disposed in one or 

 two rows. The choanosome in dried examples is moderately 

 charged with scattered spicules similar to those of the fibres. 

 The spicules from a British Museum specimen of P. australis, Ldf., 

 measure 0-075 by 0*004 mm., and those of P./rooidosa, Ldf., 0-06 

 to 0-07 by 0-0037 mm. Spicules from the " Thetis " examples 

 are rather larger and measure from 0-07 to 0-1 by 0-005 to 

 0-006 mm. ; they appear to vary in size according to age, and are 

 smallest in large specimens. 



* Whitelegge— Eec. Austr. Mus., iv., No. 2, 1901, p. 55. 



