SPHAUROSPONGIA. 137 
The hexagonal spicular plates, forming the outer surface of the Sponge, are 
nearly flat, with a small central rounded elevation, which, however, is only seen in 
the best-preserved specimens; the plates also exhibit delicate concentric lines, 
resembling lines of growth, and occasionally their margins are slightly elevated. 
The plates near the base of the Sponge are the smallest, whilst those of the middle 
and upper portions are about equal in size. They vary from 2°5 mm. to 7°5 mm. 
in width. Though apparently the plates are in close contact with each other, 
yet many specimens show narrow linear interspaces between their margins. 
The transverse spicular rays, forming vertical and concentric ridges within the 
Sponge, gradually taper from their central node and terminate obtusely ; those 
extending horizontally are not infrequently curved and less regular than those of 
the vertical ridges. The rays are slightly unequal in length, and frequently 
overlap, so that when fused together by fossilization their individual forms are not 
readily distinguishable. 
As a general rule, the specimens showing the exterior surface are infilled with 
a solid caleareous matrix, whilst in the hollow specimens the surface-plates are 
concealed by the rock. Fragments, however, occur in which both the outer and 
inner structures of the wall can be recognised. In all the specimens discovered, 
the structures are replaced by carbonate of lime. 
In a lately published paper,' Prof. Schliiter proposes to include as distinct 
species of Spherospongia, Scyphia cornucopie, Goldfuss, Pasceolus Rathi, Kayser, 
and Dictyophyton gerolsteinense, F. Roemer, as well as three new species, 
S. sculpta, S. vichtensis, and S. megarhaphis. The characters of these species 
for the most part depend upon slight differences in the size of the specimens and 
of the individual spicular plates of their surfaces, and the specimens are very 
fragmentary. Judging from the great variability in these features shown in the 
suite of specimens of 8S. tessellata from Newton-Bushell, I do not think these 
differences have any specific value, at least as regards the forms described by 
Goldfuss, Kayser,and F. Roemer, whilst I hesitate to express an opinion as to the 
new species proposed. 
The type of the species, represented on Pl. IV, fig. 2, is now in the Museum of 
the Geological Survey, Jermyn Street. 
Distribution.—Middle Devonian : Newton-Bushell, Devonshire. Also at Vilmar, 
Nassau; Hifel, Germany; River Jolva, near Bogoslofsk, Ural, Russia. 
1 «Zeitschr. d. deutschen geolog. Gesellschaft,’ 1887, p. 1. 
