=" 166) = 
each other, so that some spicules appear to have seven arms 
radiating from the central node instead of the normal number. 
The sponges of this genus are cup shaped with a thin sur- 
face membrane which is provided with regularly disposed 
canal openings. Fragments of the skeleton are not uncom- 
mon and are readily distinguished from all the other hexac- 
tinellid remains in this flint by the large size of the mesh as 
well as by its irregular arrangement. 
Leptophragma sp. 
(Plate V, fig. 18). 
Mesh work of the skeleton arranged so as to form triangu- 
lar and quadrangular interspaces. The central knot of the 
spicule solid and expanded to about twice the thickness of 
the arms. Average diameter of the mesh 1,09 mm.;_thick- 
ness of the arms of spicule 0,04 mm.; of the central node, 
0,09 mm. 
The much smaller size of the mesh work and the _ infla- 
tion of the central node of the spicule distinguish these frag- 
ments of sponge from the preceding form. 
Craticularia sp. 
(Plate V, fig. 19). 
Mesh skeleton very regular and disposed so as to form 
quadrangular interspaces. The central nodes are solid, and but 
slightly larger than the spicular arms. Thickness of the arms 
0,033 mm.; diameter of the squares or distance between the 
nodes 0,2 mm. Rare. 
In the regularity and form of the interspaces of the mesh 
and the character of the nodes, this sponge bears a great re- 
semblance to specimens of Cratécularia from Streitberg which. 
are in the Museum at Munich. Prof. Sollas has also descri- 
