a Oy, aes 
of the genera Phymatella, Callopegma, Turonia and Siphonia 
(Studien tib. foss. Spong. Taf. VIII, IX). As regards Siphonia 
also the spicular structure has been well illustrated by Professor 
sollas (Quart. Jour. Geo. Soc. 1877. Pl. XXVI). In existing 
sponges a similar form of spicule also occurs in Discodermia, 
Theonella and Kaliapsis. With such small differences in the 
structure and form of the spicule, it would be very difficult 
to determine, even were these free spicules well preserved, how 
many of these fossil genera may be represented, and it is 
hopeless to make an attempt to do this, when the spicules, 
as in the present instance, have been partially destroyed. 
The surface spicules (Pl. IV. figs. 31—34 which I regard 
as belonging to the same sponges as the minute four armed 
skeleton spicules, differ from those which I have placed under 
Ragadinia, in the absence of a central laminated disc; the 
head of the spicule being formed by three horizontally 
extended sinuous arms which are once, and occasionally twice, 
bifurcated. There are two well marked varieties in these 
surface spicules; one form (figs. 31, 32) has the branches very 
regular and even in width, with an average diameter of the 
head of 1,1 mm.; the other form is very small and slender 
and the terminal ends of the branches are deeply laciniated; 
the diameter of this form is only 0,517mm. These surface 
spicules are present in greater numbers and in better preser- 
vation than the mesh spicules, but they are also of but little 
value for determining the particular genus of sponges to 
which they belonged. To the smaller form (fig. 34) corres- 
pond the laciniated spicules which Mr. Carter has described 
from the Haldon Green Sand under the name of Dactylocal- 
ycotes Vicaryz (An. Mag. N.H. Vol. 7, p. 123, Pl. VII, figs. 
1,2). The larger form (figs. 31,32) is nearly double the size 
of the similarly shaped spicule from the Upper Chalk of 
Westphalia, figured by Prof. Zittel. (Ueber Coelop. Taf. VII, 
figs. 29, 30). 
