PHORMOSELLA. 125 
other four in the plane of the wall. It is very likely that rod-like spicules may 
also be intermingled with the cruciform and five-rayed spicules. 
The type-specimen is in the collection of the Geological Survey of Scotland, 
Edinburgh. 
Distribution.—Silurian : Upper-Ludlow strata; Wetherlawlinn, Pentland Hills, 
near Edinburgh. 
Genus.\—PuormosEtia, Hinde, gen. nov. 
Generic Characters.—Spherical or sacciform Sponges, apparently free. The 
skeleton consists of a delicate wall of spicular tissue, composed of cruciform 
spicules, so disposed that their rays mark out sub-quadrate areas, which are filled 
in with smaller spicules so as to form a connected meshwork. 
This genus is proposed to include some small Sponges which are preserved as 
compressed oval markings on the surface of a slab of arenaceous rock. Only the 
impressions of the spicules in iron-peroxide are shown; their arrangement differs 
from that in the alhed genus Protospongia, in that there is only a single series of 
squares in which the smaller spicules are somewhat irregularly disposed. The 
larger spicules are not grouped in bundles as in the vertical series of Plectoderma 
and in Dictyophyton, but they are disposed singly, so that their rays overlap and 
form vertical and transverse lines. 
10. PHormosenxa ovata, Hinde, sp. nov. Plate ILI, figs. 2, 2 a, 2 b. 
The Sponges are circular or oval in outline, without trace of a stem or point of 
attachment. They vary from 12 to 17 mm. in diameter. No summit-aperture is 
perceptible, since all the specimens appear to have been compressed laterally so 
that they are now mere films on the rock-surface. The rays of the larger cruci- 
form spicules, which mark the sides of the squares, are from 2 to 3 mm. in length. 
The spicular axes, though generally longitudinal and transverse with respect to 
the Sponge, sometimes diverge slightly, so that the vertical and horizontal lines 
are not always strictly continuous. The smaller spicules of the skeleton are very 
indistinctly seen ; they do not exhibit any regular arrangement. In some specimens 
there are minute punctate elevations and depressions, probably indicating a fifth 
ray in some of the spicules. 
1 gopuos, anything plaited, dimin. 
