Geodia? sp. 
(Plate Til . ‘figs’23: (6; 75°9). 
Moderately robust, simple and compound trifid spicules, 
with elongate, straight or slightly curved shaft. The head rays 
of the simple forms are short, conical, pointed and directed 
obliquely forwards; in the compound spicules the rays are 
stouter and more compressed, with the primary rays directed 
forward, but the secondary bifurcations extend in a horizontal 
direction. There are considerable differences in the dimensions 
of these spicules and the figures represent specimens of the 
average largest of each form. The smallest (fig. 9) has a 
length of 1.28 mm.; thickness of shaft 0,135 mm.; and 
width of head rays 0,405 mm. The larger, (fig. 3) has a 
length of 3,15 mm.; width of shaft, 0,22 mm. and width of 
head rays 0,742 mm. There are a number of examples of 
each of the four forms which I have figured and the exam- 
ples of each form correspond pretty closely in size, so that 
it is quite possible that they may belong to more than one 
species of sponge. Spicules similar to these occur in other 
eroups of sponges besides Geodia and genera allied to it. 
Thus a form similar to that placed under fig. 3 is found in 
Ophiraphidites cretaceus, Zittel (Stud. tib. foss. Spong. p. 98, 
Taf. XI, fig, 2 d) and it is also present in great numbers in 
the Lithistid sponge Doryderma dichotoma, Roemer, sp. (Stud. 
iib. foss. Sp. Taf. VII, fig. 1 c) but as none of the spicules of 
the mesh of Doryderma are found in the flint-meal, these tri- 
fids are not likely to have belonged to this species. Similar 
spicules are very abundant in the Haldon Green Sand and 
are included by Mr. Carter under the name of Geodttes hal- 
donensis (An. and Mag. Nat. Hist. Vol. VII, Pl. X, figs. 60, 
61, 63, 66): they have also been figured by Zittel from the 
Upper Chalk of Coesfeld. (Ueber Coelop. Taf. VI, fig. 6, 9, 
Taf. Wilp figs... '2)43) 6): 
