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. It is somewhat 

 similar to globates figured by Dr. Hiude from Upper and Lower Green- 

 sand, 1 but is much smaller and not ornamented. 



Figure 31. A siliceous globule similar in shape and surface to Fig- 

 ure 27, but larger. The surface seems to be composed of or covei'ed 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. 2 The dark brown granules on the outside are 

 supposed to be grains of iron 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. The 

 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 Anchorinida'. From these imperfect specimens, 

 and also from the fact that the family of Geodidai is so abundantly 

 represented, I conclude it reasonable to suppose that the other family of 

 Tetractinellida; was also present to a limited degree at least. 



LITHISTID2E, Oscar Schmidt. 



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 chalcedonic silica that 

 have an indefinite trace of an outline similar to a Lithistid, but, since 

 the chalcedony has a concentric structure, nothing definite was made 

 out. One was found incomplete as to terminations, and hence not 



i Phil Trans. Ii. S.. Part II., 1885, p ui. PL XLIII. Fig. 2c 

 - Ann. Mag. Nat. Ili.-t.. S,r I. 1877, Vol. XX. p. l".il>. 



