18 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Figure 29. Geodia sp. A globate spicule, perfect. Body ornate, 
with minute spines. Size 0.035 mm, by 0.0321 mm. If is somewhat 
similar to globates figured by Dr. Hinde from Upper and Lower Green- 
sand,! but is much smaller and not ornamented. 
Figure 31. A silicevus globule similar in shape and surface to Fig- 
ure 27, but larger. The surface seems to be composed of or covered with 
dark brown granules and a large irregular dark spot in the centre. The 
nature of this spot is unknown, but it has every appearance of peroxide ot 
iron. As has been said it is a common phenomenon, and is sometimes 
round, but is more often irregular. The color as well as the irregular form 
would, it seems to me, prevent it from being an air bubble similar to the 
one figured by Sollas.? The dark brown granules on the outside are 
supposed to be grains of iyon ore, but their formation as well as their 
nature is not understood. 
Figure 32. Geodia? sp. Spicule perfect. Pyramidal in form, with 
one branch of base shorter than others and the shaft much longer. Тһе 
replacement is by amorphous silica, but axial canal not preserved. 
The surface somewhat pitted, showing irregularity of replacement. 
Length of shaft, 0.333 mm.; width of shaft, 0.0269 mm; spread of 
arms, 0.173 mm. This belongs to some form of Geodia altogether much 
smaller than any I have found described. "There are larger ones in the 
Texas flint, but they were not so perfect in form. No clearly defined 
specimens of anchorate spicules were found, although some were found 
that indicated pretty clearly through their mutilated parts that- they 
belonged to the family Anchorinidw. From these imperfect specimens, 
and also from the fact that the family of Geodidw is so abundantly 
represented, I conclude it reasonable to suppose that the other family of 
Tetractinellidw was also present to a limited degree at least. 
LITHISTIDZH, Oscar Sonurpr. 
The order of Lithistid sponges is almost entirely absent from the 
Texas flints, so far as I can definitely determine, with the exception of a 
flesh spicule, Figure 23, which is doubtfully called a Lithistid, In 
addition to this there are a number of areas of ehalcedonic silica that 
have an indefinite trace of an outline similar to a Lithistid, but, since 
the chaleedony has a concentric structure, nothing definito was made 
out. One was found incomplete as to terminations, and hence not 
1 Phil. Trans. В. S., Part TI., 1885, p. 441, Pl. XLIII, Fig. 2c. 
2 Ann, Mag. Nat. Hist., Ser. 4, 1877, Vol. X X. p. 292. 
