1873.] DR. J. S. BOWERBANK ON THE SFONGIAD.«. 19 



long ray is projected among the interstitial membranes at about right 

 angles to either the dermal or the cloacal surface. The space between 

 the cloacal and the dermal strata seldom exceeds the length of two 

 long radii as projected from the opposite surfaces, their apices meet- 

 ing and being cemented together by keratode. There are no inter- 

 lacing spicula connecting these slender compound columns, the dense 

 case of strong acerate dermal spicula affording sufficient protection 

 and support to the delicately constructed interstitial tissues. 



Desmacidon fistulosa, Bowerbank. (Plate IV.) 



Sponge massive, sessile (?), furnished with long, slender, external, 

 fistulous cloacse. Surface smooth and even. Oscula and pores in- 

 conspicuous. Dermal membrane coriaceous, abundautly spiculous ; 

 spicula thickly but equably dispersed, same size and form as those 

 of the skeleton. Skeleton — fibrous rete stout, elongately diffuse, 

 most abundant near the external surface ; interstitial rete regular, 

 unispiculous, areas rarely exceeding the length of one spiculum in 

 width ; skeleton-spicula of both parts acerate, rather short and 

 stout. 



Colour in the dried state fawn-yellow. 



II ab. Fremantle, Australia {George Clifton, Esq.). 



Examined in the dried state. j 



I received two specimens of this remarkable species from my friend 

 Mr. George Clifton. The one figured is rather the smallest of the 

 two ; but the form of the bulbous mass of the sponge is as nearly as 

 possible the same in both. In the figured specimen there are lour 

 large cloacse remaining ; and two others have formerly existed, but 

 have been rubbed off close to the dermal surface and their orifice 

 healed over. On the second specimen nine fistulous cloacse are pro- 

 jected from the distal surface ; they are less in diameter than those 

 of the figured one, and none of them exceeds an inch in height. There 

 is a remarkable coincidence in the condition of the basal portions 

 of the two specimens : each of them has undergone abrasion to such 

 an extent as to have totally destroyed the dermal membranes of those 

 parts, as if they had been freely floating about on a coarse sandy 

 surface. On neither of them is there any indication of their having 

 had stout root-like appendages for attachments ; and the abraded 

 surfaces consist of interstitial reticulate structure without any ad- 

 mixture of the stout spiculo-fibrous skeleton. The dermal mem- 

 brane in its present state has a very coriaceous appearance, and on 

 some parts of the surface it is wrinkled by drying, much like very 

 thin leather under similar circumstances. It is rather thick and is 

 abundantly spiculous ; the spicula are short and stout, of the same 

 size and form as those of the skeleton. They are thickly and irre- 

 gularly but equably dispersed. 



The fibrous portion of the skeleton prevails more especially near 

 the dermal surface ; and the fistulous cloacae are composed almost 

 entirely of it — long lines of primary fibres parallel to each other, 

 connected by secondary ones at nearly right angles to the primary 



