12 
of opinion as to the further details of the structure of Stromatopora, and these have led to 
equally wide differences of opinion as to the affinities and systematic place of the genus. 
According to McCoy (Pal. Foss., p. 12,) the vesicular tissue of Stromatopora is composed 
of “ minute curved calcareous plates,” which he compares with the coenenchyma of Palao- 
pora and Fistulipora. He also states that the upper surface is occasionally marked “ with 
extremely obscure, distant, quincuncially arranged, small pits,” which he appears to think may 
represent the corallites in the above-mentioned and other allied genera. 
Prof. Hall agrees with McCoy in referring Stromatopora to the Coelenterata, and in 
placing it in the neighbourhood of Tubipora (Pal. N. Y., Vol. U1. p. 135.) He considers that 
the fossils of this genus are composed of “ minute cylindrical tubes with considerable space 
between ; and that the laminated structure arises from thin layers of calcareous matter de- 
posited and filling the spaces between, and enclosing the tubes.”’ 
If the Stromatopora polymorpha of Goldfuss (Petref. Pl. lxiv, figs. 8a, 8f) be a genuine 
Stromatopora, then this eminent paleontologist long since recognised the tact that Stromatopora 
is a genus of Sponges. There is, however, some doubt on this point ; since neither his 
description, though unusually precise; nor his figures demonstrate the existence in this species 
of the minute structure peculiar to Stromatopora. Nor is this point cleared up satisfactorily 
by the description given by McCoy of this same species (Pal. Foss. p. 65); whilst D’Orbigny 
makes Stromatopara polymorpha, Goldfuss, the type of his genus Sparsispongia. There is, 
however, much resemblance between S. polymorpha and some of the species of Stromatopora 
from the Devonian Rocks of Ontario, especially S. granulata, Nich. 
My own investigations of a very extensive series of examples from the Lower and Upper 
Silurian formations, and from the Devonian Rocks, have led me to the opinion that the genus 
Stromatopora is clearly referrible to the Spongida, and that it should be placed amongst the 
Calcispongie, a group represented by many and varied forms both in past time and at the 
present day. The reasons for this belief may be summed up as follows :— 
a. The fundamental structure of Stromatopora is by no means inconsistent with the belief 
that it belongs to the Culcispongie. It does not consist of reticulated caleareous spicula, as 
in the more typical members of the group; but neither does it consist of a vesicular tissue 
composed of “‘minute curved calcareous plates” (MeCoy), which could be in any way com- 
pared with the vesicular coenenchyma of many tabulate corals. On the contrary, it consists of 
successive calcareous layers, which may be regarded as composed of an amalgamated system 
of horizontal spicules, separated by intervals, and kept apart by a vertical system of delicate 
calcareous props or rods, giving rise to a system of more or less quadrangular cells. The hori- 
zontal laminge are upon the whole continuous, but they sometimes sub-divide and inosculate ; and 
the vertical pillars are decidedly irregular, being sometimes inclined at various angles, and not 
being placed at uniform distances in all parts of even the same specimen. Some of the ver- 
tical rods pass continuously through several ]aminze and the interspaces between them; but 
the greater number are confined entirely to the interval between two successive laminz, and 
are not continuous, nor correspond with those in the interval immediately above or below. 
There is no ground, so far as I am aware, for the supposition that these vertical pillars are 
perforated, or are of the nature of tubes inhabited by the separate zodids of a colony ; indeed 
in the forms which occur in the Corniferous limestone there is the strongest positive proof 
that this is not the case, and that they are of the nature of solid rods or dissepiments. There 
is nothing in the fundamental tissue or groundwork of Stromatopora, as above described, 
which would necessarily preclude us from referring the genus to the Spongida; nor can any 
stress be laid upon McCoy’s argument that these organisms cannot be sponges on account 
of their possessing a rigid and inflexible skeleton, since similar reasoning would compel us to 
remove from the Spongida a vast number of forms the zoological position of which is beyond 
doubt. At the same time, if Stromatopora consisted wholly of the laminated and reticulated 
tissue just described, and possessed none of those openings which are so characteristic of the 
sponges, then, indeed, the genus might be more properly referred to the Foraminifera, in 
many respects the close allies of the sponges, but destitute of the canal-system which is pre- 
sent In the latter. 
6. Such openings, however, can be shown to exist in certain forms of Stromatopora, and 
there is strong reason for believing that they will ultimately be found to be present in all. 
Thus in Stromatopora striatella (D’Orb.), and 8. concentrica (Gold.), both typical examples 
of the genus, Professor McUoy long ago described the existence of vermicular tubes opening 
