12G Mr. 11. J. Carter on 



XV. — Descriptions of Sponges from the Neighbourhood of 

 Port Phillip Heads J South Australia^ continued. Bj H. J. 

 Carter, F.R.S. &c. 



[Continued from p. 55.] 



Order VIII. CALCAREA {continued). 



Observation. 



We now come to Calcareous Sponges wherein the spicules 

 and savcode apparently do not present any definite arrange- 

 ment like that of the foregoing species, but, on the contrary, 

 one in which both are apparently mixed together confusedly, 

 so as to form a cancellated mass, which is traversed by a 

 branched system of excretory canals identical with that of the 

 non-calcareous sponges, the former representing the paren- 

 chyma and the latter the channels of the excretory system. 



To this structure the name of '■'■Leuconia " was given by 

 Dr. Bowerbank in 1864 (Mon. Brit. Spong. vol. ii. p. 2), ex. 

 gr. L.Jistulosa {Leucandra jistulosa, H.) , and the same name 

 will be adopted here. 



Hilckel put these sponges into his second family under the 

 name of "LeMCones," which he has divided into genera ; but 

 at present I can only give my attention to the species in 

 Mr. Wilson's collection^ under the general title of ^'Leuconia,'''' 

 and leave others to divide them into genera hereafter when a 

 complete history of the calcareous sponges shall be produced. 



Since describing the last of the Ascones (' Annals,' 1886, 

 vol. xvii. p. 512), viz. Clathrina ventricosa^ wherein the 

 amount of parenchyma far exceeds that observed in any of the 

 Sycones, as before stated {supra, p. 35), this structure has not 

 presented itself to anything like the extentof that characterizing 

 the sponges about to be noticed, although the excretory canal- 

 system may be easily homologized throughout. Hence the 

 following diagnosis under the " heading " before mentioned, 

 viz. : — 



Leuconia. 



Calcareous sponges in which the parenchyma is almost 

 equal in amount to the excretory canal-system, which 

 traverses it in all directions by repeated subdivision, until 

 one is as infinitely divided as the other. Canals poriferous 

 throughout. 



