SPONGES FROM COASTAL BEACHES OF N. 8. WALES — "WHITELEGGE. 213 



and dimensions, but not in its spicular characters. The specimen 

 proves to be identicaPwith an example exhibited in the cases as 

 the type of Ceraochalina 'multiformis, var. dura, Lendenfeld, from 

 Illawarra. 



Arenochalina mirabilis, Lendenfeld. 



The British Museum specimen from Torres Straits, and probably 

 a bit of the type, confirms my identification of the examples from 

 New South Wales, and also proves that the spicules are styli. 

 The proper stylote spicules are not confined to the secondary 

 fibres, as might be inferred from the diagnosis. There is a distinct 

 axial core present in the main fibres at the apices, the number of 

 spicules being at least equal to those in the secondaries. A longi- 

 tudinal section through the apex of a branch, displays a series of 

 main fibres which are gradually tapering, elongated, and pointed 

 at the summit ; about half or two-thirds of each fibre is cored by 

 an axial string of closely placed styli. At a short distance below 

 the apex, a few small distant sand grains are enclosed. As the 

 base of the fibre is approached, the sand-grains become larger and 

 closer together, with an occasional space in which the axial core 

 of spicules can be seen intact. In the parts of the fibre occupied 

 by sand grains the core is displaced, and is visible first on one 

 side and then on the other, or is spread out so as to form an 

 irregular sheath of spicules around the enclosed sand grains. The 

 arrangement of the sand-grains, their unequal distribution and 

 size, their absence from a considerable portion of the growing 

 apices, suggest the question as to how the sand grains are taken 

 in the fibres. Time will not permit of an extended search as to 

 what is known on this point. I failed to find any reference to 

 the question in the "Monograph of Horny Sponges." 



Mr. E. A. Minchin,^ in dealing with the matter, states that 

 sand grains "become included in the fibres, apparently by adhering 

 to the tip of the fibre at its growing point, where it is continuous, 

 in all probability, with the external cuticle of the sponge." 



After a careful study of the fibres of Arenochalina mirabilis, 

 Lendenfeld, I have arrived at the conclusion that the main fibres 

 do not take in the sand grains at their growing apices. In this 

 species (and also in many others possessing sand grains) the grow- 

 ing apical portion of the fibre is attenuated and pointed, and if 

 any sand grains are present they are remote from each other and 

 often also from the apex. At a short distance from the summits 

 of the fibres the enclosed sand grains are larger and closer, but 

 rarely exceed the diameter of the fibre. Nearer the base they 

 form one or two rows, and frequently some of the grains are five 

 or six times greater in diameter than the fibre in its normal 



2 Minchin— A Treatise on Zoology, 1900, Pt. ii., Porifera, p. 42. 



