MERRILL: FOSSIL SPONGE SPICULES. 13 
Figure 6. Imperfect. This spicule has been replaced by amorphous 
silica of an opalescent hue, the dark portion of which represents the 
replacement of the axial canal enlarged. It is covered with bulbous 
projections or blunt spines, which are evenly arranged toward the apex, 
but become more irregular toward the extremity. It has the appear- 
ance of being thin and flat rather than cylindrical. It is 0.0843 mm. 
long, by an average width of 0.0844 mm. It has not been found 
figured. 
Figure 7. This spicule is imperfect and irregular in outline, the 
irregularity seemingly composed of folds in the outer covering of the 
spicule. The outline seems to be in peroxide of iron, or some kind of 
black organic matter, most likely the latter, since it has not the beaded 
form common to the ore replacement. Тһе interior is entirely of 
amorphous silica, with a trace of an axial canal. A cross section of this 
shows a thin black ring around a siliceous body. This figure is 0.52 mm. 
in length by 0.08 mm. in width. This species is the most abundant of 
the sponge spicules found in the flint, and the figure given represents its 
most characteristic form. The summit of one has not been found, and 
only occasionally is the apex found complete, while fragments and cross 
Sections are abundant. It was found in all the nodules examined, and 
one was made up almost entirely of it. In the nodules above referred 
to there are found what appeared to be irregular black tracings of the 
outside layer of this spicule, curiously winding around in the flint and giv- 
ing it a dark ringed appearance. This outside layer is sometimes thicker 
than others, but is always distinct, and surrounds the spicule entire 
unless broken mechanically. I have not found this spicule described or 
figured. 
Figure 8. A fragment of a cylindrical spicule covered with very short 
bulbous projections. The specimen is composed of a thin wall of col- 
loidal silica, while the inside is filled with whitish amorphous silica, 
no axial canal visible. Size of specimen: length, 0.266 mm. ; width, 
0.106 mm. Of this I found but one specimen. One somewhat similar 
is figured by Dr. Hinde. 
Figure 9. Esperites? sp. Almost perfect, but the ends not fully 
shown. A bihamate spicule. Length, 0.266 mm., width, 0.026 mm. 
Others found measure 0.386 mm. in length by 0.026 in width. Others 
less typical in size show tho peculiar bihamate ends better than the one 
fipurod. "This is a very common form in the nodules, and is found in 
nearly every slide. It is probably some species of the recent family 
1 Fossil Sponges of Upper Chalk, Plate I. 
