502 Mr. H. J. Carter on 



XLVII. — Descnptioas of Sponges from the Neifjlibonrhood of 

 Port Phillip Tleads^, South Australia^ continued. By H. J. 

 CaeteRj F.R.S. &c. 



[Continued from p. 441.] 



Order VIII. CALCAEEA. 



Structure composed of contorted, repeatedly branched, anas- 

 tomosing, tubular threads, forming a reticulated mass which 

 at length assumes a more or less definite form. 



1. Clathrtna^ cavata. 

 Individualized. Massive, compressed or round, contracted 

 towards the base ; composed of tortuous, hollow or tubulated 

 thread-like filaments, almost infinitely and irregularly branch- 

 ing and anastomosing ; compactly reticulated above, becoming 

 looser and more open in structure below, where it finally ends 

 in a few of the same kind of hollow filaments, which are at- 

 tached to the object (mussel-shell) on which it may be growing. 

 Colour sponge-brown when fresh, lighter when dry. Surface 

 even, irregularly reticulated. Pores numerous, passing 

 through the wall of the hollow thread. Vents of two kinds, 

 viz. spurious and real ; the former more or less in plurality 

 scattered over the surface generally or confined to the upper 

 border, consisting of short, thin -walled, cylindrical prolonga- 

 tions extended from the outside of the wall of the tubulated 

 thread, which prolongations are in direct communication with 

 the interstices of the reticulated mass generally, but more 

 especially with dilated portions of this mass extending 

 for a short distance inwards in the form of a cavity ; real 

 vents consisting of circular holes here and there in the 

 wall of the reticulated tubulation, which not only open into 

 the so-called cavities or dilated portions, but in all probability 

 exist throughout the structure, where they would open into 

 the interstices generally of the reticulated mass. Structure 

 that above mentioned, whose staple is the " tubulated thread," 

 of which the wall is very thin and skeletally composed of 

 a single layer of radiate spicules held together by sarcode 

 supporting the softer parts, which here appear to consist 

 chiefly of a layer of spongozoa in juxtaposition, and not 

 gathered into the form of ampullaceous sacs, together with 

 a remarkable quantity of those organs which consist of 

 nucleated cells surrounded by an abundance of glistening 

 spherical granules, which Hackel has figured and named 



* Dr. J. E. Gray's name for this liind of sponges (see ' Annals/ 1884, 

 vol. xiv. p. 17 &c.). 



