arms, which are extended nearly at right angles to the shaft. 
Length 2,07 mm.; thickness of shaft 0,2 mm. and extension 
of the head rays 1,08 mm. Very rare. 
Tethya? sp. 
(Plate #1) fig. 88). 
Simple robust trifid spicule, with a very stout, short, ra- 
pidly tapering shaft, on the summit of which are three short 
cylindrical rays, directed forwards at an acute angle with the 
shaft. Length of shaft 1,95 mm.; thickness 0,27 mm.; ex- 
tension of head rays 0,517 mm. This spicule is distinguished 
from the preceding by the arms being longer, not so stout 
and also directed forwards. Rather rare. 
These three last described spicules (Plate ITI, figs. 4, 5, 8) re- 
semble each other in having comparatively short and robust shafts 
and cylindrical, stout, simple, head rays, at the same time each 
form is distinctly marked off from the others by differences 
in the shaft and disposition of the head rays, so that they 
may have belonged to as many species of sponge. This form 
of spicule differs considerably from the «zone» spicules of 
existing sponges of the genera Geodia, Stelletta and Tethya, 
nevertheless their affinities appear to approach nearer to the 
spicules of this, than of any other group of sponges. 
Siliceous Globules and Globo-stellates of Geodia 
and allied Genera. 
(Plate wn, figs. 25, 26" 27): 
There are present in the contents of this Horstead flint, 
three different forms of the small siliceous bodies which are 
so abundant in the dermal crust of the recent sponges belonging 
to Geodia and its allied genera. The first of these (fig. 25) 
are small bodies, either nearly spherical or ellipsoidal in form, 
and showing, in many examples, an irregularly shaped cavity 
