== 654 == 
leton is so close that it seems highly probable that they be- 
long to Cystispongia. There is also a remarkable resemblance 
between these fragments of mesh and the skeleton of Asty- 
lospongia praemorsa. Goldfuss and under the microscope there 
was little difference to be noticed in the dimensions, form, 
and arrangement of the spicular-mesh of this Silurian sponge, 
and the examples from the Upper Chalk. 
Coscinopora sp. 
(Plate V, figs. 22— 24). 
Portions of skeletal mesh having circular or elliptical in- 
terspaces of unequal dimensions; composed of the usual six- 
rayed spicules with open or «lantern» nodes at their centres. 
Diameter of some of the larger interspaces 0,45 mm. Frag- 
ments of outer or surface layer consisting of a delicate mem- 
brane perforated with circular openings of different sizes, the 
larger, which appear to be disposed at regular distances from 
each other, have a diameter of 0,38 mm. Fragments of the 
root-fibre composed of nearly straight spicular fibres with 
transverse connections. 
These different portions of the structure of a Hexactinel- 
lid sponge appear to correspond with the Genus Cosc?nopora 
Goldfuss. The type of the genus C. 72ufundibuliformis, Goldf. 
(Petref. Germ. 1° Theil, p. 30, Taf’ 30)" ie; 10) eis) 2 seus 
shaped sponge with thin walls, which are covered by a deli- 
cate perforate surface membrane similar to that of fig. 23. 
The inner skeleton has spicules with «lantern» nodes, form- 
ing elliptical interspaces, which however are less regular 
in their arrangement than in the Horstead examples (fig. 22). 
The sponge appears to have been attached to the sea bottom 
by a root-like extension of the base, which is tormed of 
nearly parallel fibres of silica with transverse connections at 
frequent intervals similar to that shown in fig. 24. Cosczno- 
fora infundibuliformis appears to be abundant in the Upper 
