616 MR. W. S. KENT ON A NEW GENUS OF SPONGES. [June 20, 



Order SILICEA. 

 Gen. nov. Caulospongia. 



Sponge consisting of a central stem or axis, around the distal por- 

 tion of which the sponge-body is disposed in separate whorls, or in 

 more or less regular or irregular spiral convolutions. Skeleton com- 

 pound, consisting of a primary network of keratose fibre, with sili- 

 ceous spicnla irregularly imbedded in it, and an accessory one of 

 siliceous spicula only. Spicula of one form, simple, spinulate, 

 arcuate. 



1. Caulospongia verticillata. (Plate XLVIII. fig. 1.) 



Sponge-body forming interrupted ascending spiral, or regular and 

 separate infundibular expansions. Central axis and stalk fistulose, 

 the internal cavity frequently communicating with the exterior by 

 means of extensive oscula. Skeleton kerato-siliceous, consisting 

 principally of horny reticulated fibre with siliceous spicula imbedded 

 in it, but having an accessory and superficial one of spicula imbed- 

 ded in sarcode only. Spicules spinulate, slightly arcuate ; average 

 length ■£$ inch. 



Hab. North Australia. Free Public Museum, Liverpool. 



2. Caulospongia plicata. (Plate XLVIII. fig. 2.) 



Sponge-body forming contorted laminate convolutions, having an 

 irregular ascending spiral direction. Stalk fistulose above the com- 

 mencement of the body, with numerous oscular passages, compact 

 beneath. Skeleton kerato-siliceous as in the last species. Spicula 

 spinulate, slightly arcuate ; average length -^ inch. 



Hab. Unrecorded. B.M., presented by Miss Saul. 



In the existence of a primary and secondary siliceo-fibrous skele- 

 ton, this new genus appears most closely to approach Diplodemia of 

 Bowerbank, an incrusting form with simple acerate spicula, regarded 

 by its author as forming a connecting link between the Keratose 

 and Halichondraceous tribes of Sponges. 



In the drawing which I exhibit (Plate XLVIII.) fig. 1 represents 

 Caulospongia verticillata reduced to one half its natural size, and 

 fig. 2 the true proportions of C. plicata. The single specimen exa- 

 mined of the first of these exhibits a series of slightly prominent 

 ridges radiating from the centre to the circumference of the infun- 

 dibular or spirally ascending expansions of the sponge-body, these 

 being most conspicuous on the upper surfaces. In both species the 

 passages communicating with the internal cavity of the fistulose 

 stem would appear to represent the only distinct oscular system. 



