462 Mr. H. J. Carter on Deep-sea 



the possibility of its being confounded with any other of the 

 kind either in the Geodina, Stellettina, or PachastrelUna. 

 Thus the existence of Corallistes Bowerhankii near Cape St. 

 Vincent is established. 



From the position of the large furcate spicules being in 

 rather than on the surface of the specimens, it might be 

 inferred that these, in particular, were on their way to that 

 transformation which the surface layer of all growing sponges 

 must undergo if it passes into and becomes incorporated with 

 the tissue of the interior, while the characteristic layer of 

 these dermal spicules imbedded in the sarcode charged with 

 the flesh-spieule in the living sponge would then altogether 

 disappear. Thus a little further in than tlie surface no 

 trace of the furcate spicule would be seen ; for by this time 

 they would all have become transformed into the staple form 

 of the interior structure — unless tlie old dermal layer is ab- 

 sorbed, the internal structure pushed forward, and a new 

 dermal layer formed, or the old dermal layer is expanded 

 and its deficiences made up by the addition of new dermal 

 layer — neither of which appears to be so likely as the first 

 assumption. Be this as it may, the characteristic dermal 

 spicule of Corallistes Boicerhankii is present here. 



On crushing some portions of these specimens taken from 

 parts which had been washed clean of mud &c., the fragments 

 of the larger iiligreed spicules, under the microscope, forcibly 

 recalled to mind those which 1 had found in the Upper Green- 

 sand of Haldon Hill near Exeter ('Annals,' 1871, " On Fossil 

 Sponge-spicules, (fcc." vol. vii. pi. viii.). 



For good illustrations of the dermal and flesh-spicules of 

 this species, see Dr. Bowerbank's figures (Proc. Zool. Soc. 

 1869, pi. vi. figs. 5-8, "Monograph on the Siliceo-Fibrous 

 Sponges "). 



Discodermia poly discus, Bocage, 1869, = Dacti/Ioca7i/x 

 jooly discus, Bowerbank, 1869. 



The type specimen of this species is in the British Museum ; 

 and its general form is shallow, cup-like, with comparatively 

 thick walls and an equally short, stout, stipitate base. It is 

 an inch in diameter, and | of an inch high ; and its structure 

 internally consists of the filigreed spicule common to the 

 Lithistina (but of a peculiar form, which will be mentioned 

 dii-ectly), faced by a dermal layer of thin, smooth, subcircular 

 disks with more or less curvilinear or toothed margin, furnished 

 respectively with a short, round, pointed shaft, which projects 

 internally, and imbedded in a dermal sarcode densely charged 

 with a minute, curved, acerate, microspined flesh-spicule. 



