1876.] DR. J. S. BOWERBANK ON THE SPONGIAD.E. 771 



sponge represented by figure 4. In the specimen represented by 

 figure 5 (Plate LXXIX.) it is apparently the same as in that repre- 

 sented by figure 4 ; but it has not so completely involved the verticil- 

 late species, the margins of the plates of which are still uncovered. 



For the most perfect specimen of these enveloped species of 

 sponges I am indebted to my late friend Dean Buckland, who could 

 not imagine what it could be, unless it represented an animal allied 

 to the Trilobites, the apparent smooth head and striated body 

 having impreseed that idea upon his mind ; but on my pointing out 

 to him a small spot on the middle of the smooth end of the mass, 

 which I conjectured might be the basal end of the pedicle, he pre- 

 sented it to me that I might, if possible, clear up our doubts 

 regarding its structure. I accordingly marked it for cutting in such 

 a direction as to make a section of the supposed pedicle, as well as 

 through the centre of the plates of the sponge ; and the result was the 

 production of the specimen represented by figure 4, Plate LXXIX., 

 completely confirming the ideas regarding the nature of these fossils 

 that had previously arisen from my examinations and comparisons of 

 the fossils with the singular verticillate sponges from the x\ustralian 

 seas. 



Very few of these enveloped specimens of verticillate sponges are 

 in so perfect a state of preservation as that represented by figure 4. 

 By far the greater number of them appear to have been in a very 

 young state when thus enveloped by the parasitical sponge ; and 

 their size has been still further curtailed, and their true form 

 obscured in the fossil state, by the destructive attrition that they 

 have undergone in the diluvial gravel, in which they are by no means 

 scarce. I have in my own collection 33 specimens of various sizes 

 and states of preservation, among which there is one that is evidently 

 the termination of a fossil specimen quite as large as the recent one 

 figured, the greatest breadth of the spongeous plates being two and 

 a quarter inches. 



These fossils, from the general character of the siliceous matter in 

 which they are embedded, probably belong to the chalk formation ; 

 but I have never yet obtained one from that deposit, and therefore 

 the formation whence they are derived cannot be positively deter- 

 mined. It is a remarkable circumstance that these diluvial fossils 

 should have their nearest analogues among the recent Australian 

 sponges, and that the same may be said of the fossil fruits of the 

 London-clay formation. 



Oplitospongia fucoides, sp. nov. (Plate LXXX.) 



Sponge pedicellate ; pedicle long, slender, smooth, ramifying and 

 expanding into numerous compressed fucoideal branches disposed 

 in nearly the same plane, so as to be rudely fan-shaped. Surface 

 uneven, minutely hispid. Oscula simple, minute, dispersed. Pores 

 inconspicuous. Dermis irregularly fibro-reticulate ; rete abun- 

 dantly punctiunculate, sparingly spiculous. Dermal membrane 

 abundantly spiculuus ; spicula spinulate, smaller, shorter, and more 

 attenuated than those of the skeleton. Skeleton -fibres smooth, 



