mekrill: fossil sponge spicules. 15 



apparently, communication of the centre with the outside. As has been 

 mentioned, these spicules have not been replaced, but are most likely 

 still in the original colloidal condition. The bright transparent yellow 

 color is perhaps due to a change brought about by the action of some 

 organic acid which may be a beginning of the replacement process. 

 When viewed with high power lens, these bright yellow spicules, radiating 

 in perfect symmetry from the hollow centre, are exceedingly beautiful, 

 aud in their various forms present a contrast both novel and interesting. 

 These all belong to the family Geodidae, Lamarck, and with one or two 

 exceptions none of them have been figured as fossil, but most of them 

 are similar to the recent forms referred to in the description. In the 

 Fossil Sponges of Upper Chalk, Dr. Hinde figures a globo-stellate spicule, 

 body ornate and covered with short sharp spines. This is, however, 

 much larger than the spicules of the Texas flint. Professor Zittel also 

 figures two globo-stellates, somewhat similar in form to Figure 16 of the 

 Texas flints. 1 They are much larger, however, and none have been 

 found with barbs on the ends of the spines. This may be due to the 

 fact of imperfect preservation, but it would seem from the number of 

 specimens examined some indication at least of barbs would have been 

 detected if present. 



In Oscar Schmidt's " Die Spongien des Atlantischen Gebietes " noth- 

 ing is given similar to the globo-stellates of the Texas flints. In his 

 " Sponges of the Adriatic Sea," however, he figures globo-stellates of Geo- 

 dia placenta. 2 These have spherical bodies with round straight spines, 

 but they are much larger. The measurements given were taken from 

 tip to tip of spines at right angles to each other, and then the length of 

 a spine is given. 



These spicules doubtless belong to genus Geodia or some allied genus, 

 as Tethya or Stellata. The body is somewhat globular and the spines 

 rest squarely on bases more or less enlarged. 



Figure 13. Geodia? spini-curvata, n. sp. Imperfect, elliptical, sphe- 

 roidal, ornamented with what might with higher power lens prove to be 

 minute blunt spines. Body has also long spines, smooth, slightly curved 

 and irregularly arranged. Size : 0.096 mm. by 0.065 mm. ; length of 

 spine, 0.035 mm. Nothing similar to this has been found figured. From 

 the slight curve of the spines I propose the specific name spini-curvata. 



Figure 1 2. Geodia ? cretacea, n. sp. Perfect. Much like Figure 1 3. 

 Body ornate, smooth, and bearing numerous long and slightly curved 



1 Abh. K. Bayer. Akad. Wiss. d. Miin., XII., Bd. III., Taf. V. Figs. 27 and 30. 



2 Die Spongien des Adriatisclien Meeres, p. 49, Taf. IV. Fig. 7a. 



