Sponges from South Australia. 143 



could not have been made had not the specimen been in a 

 favourable state for such observations. 



The words " large" and "small," tolerable" and "mode- 

 rate," &c., with reference to the size of the spicules, have been 

 used for convenience; but they are all indefinite terms, which 

 are only rendered satisfactory when accompanied by actual 

 measurements. Still, it should be remembered that when 

 they are used the magnifying-power should be the same for all, 

 otherwise wliat is small at one time may appear large at 

 another, and vice versd. 



38. Leuconia lohata. 



Specimen massive, sessile, lobate, presenting two or more 

 apertures of unequal size, not peristomed. Colour whitish 

 yellow. Surface even, compact, chiefly consisting of mortar- 

 spicules and small radiates, interspersed here and there with a 

 large one which belongs to the internal structure. Pores not 

 conspicuous. Vents two or more, naked, of different sizes, 

 leading into a single, irregular, and indistinctly defined cloacal 

 cavity, whose surface is scattered over with holes of different 

 sizes, more or less sunk into the internal structure and in 

 direct continuation with the large ends of the canals of the 

 excretory system ; echinated throughout with the fourth arm 

 of sagittal quadriradiates, which is minute. Internal structure 

 cancellous, traversed by the canals of the excretory system, 

 which end in the diverticula of the cloaca already mentioned. 

 Spicules of three kinds, viz. acerate, triradiate, and quadri- 

 radiate : — 1, acerates, minute, sinuous, lance-pointed at one 

 end, about 13 by ^-GOOOth in. ; 2, triradiates of two sizes, 

 viz. small and large, the rays of the latter generally averaging 

 105 by 9-6000ths in. ; 3, quadriradiates of three sizes, the 

 largest of which is of much the same size as the larger 

 triradiates. No. 1, which is confined to the surface, is the 

 " mortar-spicule ;" no. 2, the triradiate, in its small size is 

 confined to the surface, where it is mixed up with the mortar- 

 spicule, and in its larger one to the structure of the interior, 

 extending here and there also to the surface ; no. 3, the 

 quadriradiates in their smallest size are mixed up with the tri- 

 radiates and mortar-spiculesof the surface, in their largest size 

 they belong to the parenchyma, where they are mixed up with 

 the triradiates of this structure, and in their thin sagittal form 

 to the surface of the cloaca, where, as usual, the arms are very 

 long, almost straight, and expanded perpendicularly to the 

 shaft, which is comparatively short and straight, averaging 

 16 by 3-6000ths, while the arms average 60 by 4-6000ths ; 

 the fourth arm, which is shorter still, not only echinating the 



