HOLCOSPONGIA FLORICEPS. 227 
width, extend down the sides. The basal portion of the colony has a rugose 
dermal layer. The canals traversing the sponge are 1°5 mm. in width; they are 
hardly distinguishable, owing to the open arrangement of the skeletal fibres. 
The fibres are relatively very coarse and open in their disposition ; they vary 
between ‘15 mm. and ‘4 mm. in thickness. The spicules are in such intimate 
contact that their individual outlines are seldom distinctly shown in thin sections ; 
a single ray of the large axial spicules measures ‘46 mm. by ‘045 mm. The 
marginal sinuous spicules are from ‘005 mm. to ‘01 mm. in thickness. 
The distinguishing characters of this species are the truncate-conical form of 
the individual spongites, the wide well-marked open furrows down their sides, and 
the coarse character and open structure of the fibres. It grows also in larger 
masses than any other species of the genus. As a rule the specimens are 
considerably weathered, so that the surface furrows become obliterated, but it is 
then recognised by the form of the spongites and the coarseness of the fibres 
(Pl. XVI, fig. 6 a). 
Though this species was named and a rude figure of it given by Prof. 
Phillips in 1829, it does not appear to have been hitherto described. Owing to 
the imperfect figure, neither generic nor specific characters could be with certainty 
determined from it, hence Prof. Zittel referred it to the genus Peronella, and I 
had previously placed it with other species of Stellispongia. The present 
description has been based on the type-specimen from the Lower Coral Rag of 
Hackness, now preserved in the York Museum, and on other specimens from the 
same locality which have been collected by Mr. 8. Chadwick. These specimens 
are for the most part in a calcareous matrix, which occasionally weathers to a 
rusty powder, and conspicuously shows the white fibres of the sponge. Some- 
times the weathering has acted on the fibres and laid bare their large axial 
spicules ; in one instance the spicule was distinctly four-rayed. The examples 
from the Lower Calcareous Grit of Filey are enclosed in a granular siliceo- 
calcareous matrix, and become partially silicified : they are usually smaller than 
the specimens from the Lower Coral Rag of Suffield, and rarely show the surface 
furrows; but the character of the fibres is similar, and in all probability they 
belong to the same species. 
From Holcospongia (Spongites) glomerata, Quenstedt, sp., this species differs 
in its mode of growth, the more prominent surface furrows, and the coarser fibres 
of the skeleton. 
Distribution.—Corallian. Lower Calcareous Grit at Filey Brigg and Scar- 
borough, also in the Lower Limestones or Lower Coral Rag (Perarmatus-zone) 
at Scarborough, Suffield, Hackness, Yorkshire, and in the Coral Rag at Lyneham, 
Wiltshire. 
