small surface tubercles are perforated or not. 
remains an open question, but I should be 
disposed to think that some of them, at any 
rate, were so, thus corresponding with “pores.” 
The crusts or expansions of this species often 
cover large surfaces; but it is certain that in 
many cases a great portion of the under snr- 
face must have been free and unattached to 
any foreign body. The general thickness of 
the crusts varies from three to four lines to 
two inches or more ; but the latter specimens 
are to be regarded as being composed of a 
succession of crusts superimposed, the younger 
upon the older, as is shown by the occurrence 
of tuberculated surfaces at various levels 
througbout the mass. 
Locality and formation—Common, in a 
==\ silicified condition, in the Corniferous lime- 
a stone of Ridgeway and Port Colborne. 
Fig. 2.—a. Part of the under surface of a large 
specimen of Stromatopora tuberculata, showing the 
wrinkled basement layer, and the openings of the 
oscula, natural size ; 6. a portion of the upper sur- 
face, natural size ; c. a vertical section of a frag- 
ment of the same magnified to show the internal 
structure. 
3. STROMATOPORA PERFORATA (Nicholson). 
Stromatopora perforata (Nicholson,) Annals and Magazine of Natural History, Jan., 
1874. 
Fossil composed of crusts of varying thickness, made up of thin concentrically arranged 
calcareous laminze, the interspaces between which are rendered vesicular by vertically dis- 
posed caleareous rodsjor dissepiments. From four to five laminze with their intervening in- 
terspaces, in a line. Upper surface undulating, and covered with very numerous rounded 
apertures, which vary in width from two-thirds of a line to one line, and are placed at dis- 
tances apart of a line, more or less These apertures are usually placed on the summit or at 
one side of conical eminences, or they are elevated above the general surface, the lip of the 
opening on one side being generally higher than on the other. These apertures are the ori- 
fices of more or less vertical or somewhat oblique canals which penetrate the reticulated 
structure of the mass, and are lined by a delicate caleareous membrane marked with faint 
encircling strive. Hach canal descends at first and for a certain distance (about three lines) in a 
straight line, and then iscurved so as to become nearly parallel to the lower surface of the mass, 
at the same time contracting in its diameter. Between the oscula, as just described, the sur- 
face is covered with a fine miliary granulation, composed of minute pustules, placed close 
together, and arranged in irregular vermicular and sinuous lines. 
Stromatopora perforata is, perhaps, the most remarkable species of the genus which 
has been as yet discovered; and it can not be doubted that it is a genuine member of the 
Calcispongie, though in some-respects an abnormal one. In its internal structure it agrees 
altogether with S. tuberculata, S. granulata, and S. mammillata ; and with the two former of 
these it agrees further in the possession of a series of apertures which cannot be anything but 
‘‘oscula.” No “pores,” however, have been detected, unless some of the surface-tubercles 
should in reality be perforated, which is likely enough. 
S. perforata is readily distinguished from S tuberculata by the much greater number and 
closer arrangement of the oscula, by the elevation of these apertures above the general surface, 
and by the finer granulation of the upper surface. The number and closeness of the oscula 
