Lf 
— 
cate layer in which the pores were perforated. The granulated layer which appears to form 
the surface in so many specimens, would thus appear to have been covered by a kind of “ der- 
mal’’ membrane, and to have permitted a tree circulation of water over its surface, the gra- 
nules being more or less confluent, and giving rise to a complicated system of sinuous or ver- 
micular horizontal channels. 
In a great many specimens the surface layers exfoliate round numerous points, giving 
the upper surface of the fossil quite a characteristic appearance, which is wanting in S. tuber- 
culata. Generally speaking, S. granulata may be distinguished from S. tuberculata, to which 
it is nearly allied, by the more delicate character of its reticulated tissue, and by the fact that 
the minute crowded tubercles which cover the surface are so closely placed as to be nearly in 
contact. As arule the species occurs in the form of very extensive undulating crusts, one 
specimen observed by me covering a slab about three fect in length, by two feet in width, 
with an average thickness of half an inch. I possess, however, one example, in which the 
organism is attached by a broad base to a large Heliophylium, from which it spreads out 
laterally in all directions as a horizontal expansion, the under surface being covered with a 
wrinkled ‘‘epitheca,” and having obviously been free. 
Locality and formation.—Not uncommon in a silicified condition in the Corniferons lime- 
stone of Ridgeway, Port Colborne, and Savage’s Quarry, Wainfleet, also rare in the Hamilton 
formation of Bosanquet, at Bartlett’s Mills, near Arkona. ‘ 
5. STROMATOPORA MAMMILLATA (Nicholsen). 
(Plate I., Fig. 4.) 
Stromatopora mammillata (Nicholson), Annals and Magazine of Natural History, Aug., 
1873. Plate IV., Fig. 4. 
Fossil forming thin crusts, about two or three lines in thickness, often covering extensive 
surfaces. Crust composed of successive concentric calcareous laminz, separated by interspaces, 
and broken up by vertical dissepiments. Surface undulating and exhibiting a series of large 
conical elevations about one-fifth of an inch in height and the same in diameter at the base, 
placed at distances apart varying from one fifth of an inch to half an inch. Most of these 
conical elevations show no signs of being perforated ; but some appear to have apertures at 
their summits. The surfaces between these elevations, as well as the elevations themselves, 
are roughened with numerous small granules, tubercles and irregular, sinuous ridges. 
Nothing could be more distinct than the aspect of this very remarkable species, the large 
conical elevations which cover its surface giving it exactly the appearance of an undulating 
plain covered with small volcanoes. Superficially examined, it presents a striking resemblance 
to many recent sponges; but it cannot be asserted positively that the conical elevations just 
alluded to are really of the nature of oscula. Some of them certainly look as if they were per- 
forated ; but most show no signs of any aperture. This, however, is very probably due to 
the manner in which the fossil has been preserved ; and the analogy of S. granulata would lead 
one to conclude that the conical elevations of S. mammillata are truly oscula. The internal 
structure of all the examples which I possess of this species is much more imperfectly pre- 
served than is the case with the other species here described ; and I have simply been able 
to satisfy myself that it is essentially the same as is characteristic of Stromatopora in general. I 
have seen crusts of this species covering an area of several square feet: but it is by no means 
common in its occurrence. 
Locality and Formation.—Rare, in a silicified condition, in the Corniferous limestone of 
Port Colborne. 
6. STROMATOPORA CONCENTRICA (Goldfuss). 
In addition to the previously described species, there occur in the (orniferous limestone 
of Western Ontario specimens which are hardly or not at all distinguishable from Stromato- 
pora concentrica (Goldfuss). As, however, all of these specimens are fragmentary, and none of 
them exhibit their surface, it can not be positively asserted that they belong to this familiar 
Devonian species. 
Locality and Formation.—Corniferous Limestone, Port Colborne. 
2 
