92 Dr. H. A. Nicholson on some 



A structure apparently analogous to the above has been 

 described (M'Coy, Pal. Foss. pp. 12 & 65) as occurring in 

 Stromatopora striatella, D'Orb., S. concentrica, Goldf., and S. 

 ( Caunopora) placenta, Phill. In the first of these, according 

 to M'Coy, the general laminated structure of the mass is 

 traversed nearly at right angles by " vertical vermicular per- 

 forations about one fourth of a line in diameter," at distances 

 varying from one to two lines apart ; and essentially the same 

 thing is seen in the other two species above mentioned. In 

 the present species, however, there is no evidence that the 

 apertures on the surfaces of the successive osculiferous layers 

 communicate internally with vermicular tubes, though it is 

 possible that they do ; whilst the apertures are placed at the 

 summit of small rounded or conical elevations, and are com- 

 paratively remote and large. 



It can hardly be doubted that the perforated eminences of 

 Stromatopora ostiolata correspond with the " oscula " of the 

 genuine sponges. Indeed the surface of this species reminds 

 one very strongly of the well-known genus Porospongia or 

 Manon. The probability that Stromatopora is truly referable 

 to the Calcispongise is thus rendered stronger than it would have 

 appeared from the evidence formerly in our possession. If, 

 however, it should be found that these oscula are not present in 

 all the species at present referred to Stromatopora (and they 

 have certainly not hitherto been recognized in the majority of 

 forms), then it might be advisable to divide the genus into 

 two, retaining Stromatopora for the species without oscules, 

 and forming a fresh genus for those in which these apertures 

 are present. The former would thus be nearly allied to the 

 Foraminifera, whilst the latter would lead from the Forami- 

 nifera to the Calcispongiffi. 



The specimens of Stromatopora ostiolata from which the 

 above description was taken were presented to the Museum of 

 the University of Toronto by their discoverer, Mr. John 

 Wilkie. The species itself cannot possibly be confounded 

 with any previously described form. 



Loc. and Form. In the yellow crystalline dolomite of the 

 Guelph formation (Middle Silurian), Guelph, Ontario. As- 

 sociated with numerous specimens of Stromatopora concentrica 1 

 Goldf. 



2. Stromatopora tuberculata, Nich. PI. IV. figs. 2, 2 a. 



Spec. char. Fossil forming crusts of varying thickness and 

 often covering large surfaces, composed of numerous concentrie 

 calcareous lamina?, separated by delicate calcareous rods or 



