*THE COMMERCIAL SPONGES AND THE SPONGE FISHERIES. 417 
shaped like waste-paper baskets, inverted truncated cones deeply hollowed 
on their upper faces. The attached base is one-third to one-half narrower 
than the upper rim, the sides are almost straight or slightly convex, and the 
interior is hollowed out almost to the base in the larger specimens. The sides 
are sometimes nearly smooth, but are generally furnished with interrupted 
vertical ridges tufted at their upper ends, and are perforated by numerous 
orifices about ;'5 inch in diameter. There are no oscula on the outer surface, 
although there are often irregular openings penetrating to the interior or even 
to the central cavity. The walls are thin at the rim of the vase and thicken 
toward the base. The oscula or vents are numerous and cover the whole 
interior of the sponge, excepting the vicinity of the rim. They are about 
¥% to 4% inch in diameter and in the skeletons of older specimens are frequently 
converted into demicylindrical radiating furrows by the breaking down of 
the walls toward the cavity of the vase. 
The skeletons are of a dirty brown color, harsh to the touch and highly 
elastic and resilient. These sponges are used by manufacturers of explosives, 
by masons, and for cleaning purposes about machine shops. They are espe- 
cially useful where there is much oil, as greasy matter is more readily washed 
out of them than from any other sponge. For this reason, and on account 
of their harsh, stiff surface, they are useful for domestic purposes in washing 
pots and pans. They are found distributed over the entire Bay grounds. 
Key grass (pl. XLrx, L, and 11).—These sponges are much more diverse 
in appearance than the corresponding grade from Anclote, are softer, more 
compressible, and much less durable. A typical form arises from a short 
narrow base or peduncle, spreading into a more or less hemispherical massive 
sponge with a flat or slightly concave top. The whole exterior is nearly covered 
by thin-walled oscular tubes about 34 to 1 inch in length, the openings having 
a diameter of about 7; inch. These tubes are directed variously, sometimes 
opening almost vertically downward, are sometimes deficient on one side, as 
in Lendenfeld’s Hippospongia canaliculata cylindrica, and are not infrequently 
branched or Y-shaped. In some cases they extend more or less completely 
over the top of the sponge, but in the skeleton the latter is usually occupied 
by a great number of closely approximated orifices, about 14 inch wide, separated 
by extremely thin walls, this feature being the principal reason for the great 
weakness of the sponge. In life this portion is covered by a membrane per- 
forated by extremely minute pores, and even when the tubes extend over the 
top the space between is covered by a membrane of this character. In older 
specimens the oscular tubes on the outer surface become shorter and less promi- 
nent, though retaining the general characters just described. 
In other cases the walls of the sponge become much folded and occasionally 
lobular, and the outer surface bears pencils, tufts, and vertical ridges of fiber, 
B. B. F. 1908—27 
