New Genus of Siliceous Sponges. 395 
On A New GENUuS OF SILICEOUS SPONGES FROM 
THE TRENTON FORMATION AT OTTAWA. 
By GmorGe Jennincs Hinpp, Pu.D. 
[Plate D.] 
The Canadian Geological Survey, through Mr. J. F. 
Whiteaves, F.G.S., has lately forwarded to me, for examina- 
tion and description, a small collection of fossil sponges 
which has been obtained by Mr. W. R. Billings from the 
Trenton Formation at Ottawa. The rarity of these organ- 
isms in this geological horizon renders a special interest to 
their study. The forms obtained are, for the most part, un- 
attractive in outward aspect, showing little more than their 
cylindrical or compressed outlines; and their real charac- 
ters, whether sponges or mere inorganic nodules, cannot in 
all cases be known until sections have been made. These 
show that the sponges are now completely filled up by 
the dark limestone matrix of the rocks in which they occur, 
which renders it very difficult to make out the direction of 
the canals which traversed their walls. Sometimes, how- 
ever, transparent calcite has partially occupied the canals. 
The delicate spicular network of which the sponge-skeleton 
is composed, has also been largely destroyed in the fossili- 
zation, and the portions which remain have quite lost their 
original siliceous structure, and are now replaced by crys- 
talline calcite. The effect of this change has been that the 
definite form of the individual spicules and their mode of 
union with each other, can no longer be recognized, and 
thus render their determination somewhat uncertain. In 
spite of these hindrances to a precise diagnosis, I venture 
to describe these forms as a new genus of Lithiotid sponges, 
for which I propose the name Steliella’, 
STELIELLA, g. n. 
Generic characters. —Sponges simple, subeylindrical, com- 
pressed, club-shaped or occasionally funnel-shaped, appar- 
' ornty, an upright stone or post, dimin. 
