BY E. F. KALLMANN. 361 



The bast-layer consists of an irregular, unilamellar reticula- 

 tion (PI. XX., figs. 4,5) of stout fibres immediately underlying 

 the dermal membrane, and of numerous, inwardly directed, 

 short, lamellar extensions of the same. The dermal skeleton 

 proper is a single layer of horizontally disposed spicules cross- 

 ing each other in all directions, and thus producing a some- 

 what lattice-like pattern. 



The spicules are the same in all parts of the sponge — oxea, 

 Slightly and somewhat angularly curved, nearly cylindrical 

 throughout the greater part of their length, and gradually 

 tapering to sharp points. In the typical form of the species, 

 their maximum size is 195 by 8/x, and their length ranges from 

 130 to 195 /i (but is very rarely less than 150 fx); in the variety, 

 the spicules are a little larger, attaining to a size of 220 by 

 9-5 /x. 



The typical form of the species comes from Port Jackson. 



Rhizochalina petrosia. (Text-fig. 9). 

 The evidence indicates, beyond reasonable doubt, that, 

 under this name, Lendenfeld has combined portions of the 

 descriptions of two quite different species. In the Australian 

 Museum, labelled, in that author's handwriting, with the MS. 

 name corresponding (according to his key-list) to Rhizochalina 

 petrosia, is a small, gauzy-textured, branch-shaped sponge, 

 apparently belonging to the genus Ciocalypta, the spicules of 

 which are oxea of exactly the dimensions stated in the descrip- 

 tion, viz., 700 by 15/z; and from the British Museum comes a 

 small fragment labelled Rhizochalina petrosia, which both 

 belongs to the genus Rhizochalina (i.e., Phloeodictyon) and 

 exhibits skeletal characters such as render the specific name 

 petrosia extremely appropriate, but in which the oxea are, at 

 most, only 165 by 8-5 /x in size. Thus the former specimen 

 possesses the skeletal features ascribed to the species, but is 

 entirely different to it in external form ; while the British 

 Museum specimen (the external form of which I do not know), 

 in spite of the above-mentioned serious disagreement with the 



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