New Species of Sponges. 61 
account those produced on the original structures of these 
sponges by what may be termed the mechanical influences 
of fossilization. There can be no doubt that they were 
hollow sacci-form or vasi-form structures with very delicate 
walls of spicular tissue, supporting the soft animal mem- 
branes. They existed at the surface of the soft ooze of the 
sea-bottom, probably their basal portions were embedded in 
it, and they were furnished with elongated spicules whose 
extension into the mud served to anchor them in one spot. 
After the death of the animal, and the decay of the soft 
tissues, the delicate skeletal framework would be gradually 
buried in the accumulating sediments, until by their weight 
it became completely flattened. Under favorable circum- 
stances, the outline of the sponge and the natural arrange- 
ment of the spicular skeleton would be preserved, and this 
is fortunately the case with the specimens of Cyathophycus 
from the Utica shale, and to a partial extent with one of 
the specimens of Protospongia tetranema. More frequently, 
however, probably owing to currents and other causes 
acting at the surface ef the ooze, the skeletai framework is 
partially or wholly broken up, so that only small patches 
of the connected skeleton, or merely the dislocated and de- 
tached spicules irregularly scattered over the rock surface 
remain for determination, and this is the present condition 
of the majority of the specimens from the Quebec gronp. 
For some reason, probably connected with the arenaceous 
character of the rock in which they occur, the nearly allied 
sponges belonging to the Devonian genus, Dictyophyton, 
Hall, usually retain their outer forms complete—that is, 
without being compressed—but most of these sponges ex- 
hibit only internal casts of their spicular skeleton, so that 
at present we know very little of their oriyvinal structures. 
As already mentioned, nearly all these Quebec sponges 
belong to the sub-order of the Hexactinellidie, in which the 
fundamental type or elementary spicule of the skeleton 
consists of six equal rays, radiating from a common centre 
at right angles to each other, forming three equal axes. 
But this typical form is subject to great modifications 
