46 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE. [VOL. XI 
thick outer annulus represents a zone of vesicular tissue in which the 
structure has been destroyed by mineralisation: in this case, the habit 
of growth would suggest Diphyphyllum. The size of the corallites 
suggests A phyllostylus gracilis, Whiteaves,' but it is difficult to ascribe 
it to that species in the absence of the characteristic spines. It is quite 
possible, however, that in certain of the corallites these spines have 
been destroyed and that in one instance they have been so united by 
depositions of calcite as to resemble continuous septa. 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 305 S. Royal Ontario Museum of Palaeontology. 
One fragment of limestone from the Limestone rapids of the Severn 
river contains the casts and moulds of an unusual type of coral, possibly 
referable to Pycnostylus. 
The largest example is 25 mm. long, circular in cross section and 
about 20 mm. in diameter at the anterior end. For about 17 mm. there 
is little diminution in diameter, but below that point the decrease in 
diameter is greater and there is some evidence of curving. 
The only structures actually preserved are an exceedingly delicate 
epitheca, very short and delicate septa and possibly a few tabule at 
the posterior end of the specimen. 
The epitheca is of extreme tenuity, marked vertically by septal 
furrows which are but little more than a millimetre apart, and raised 
into rows of blunt protuberances in the interseptal tracts. The external 
appearance is therefore very different from that of any coral with which 
I am familiar. A small portion magnified five times is shown in Plate 
I, Figure 4. 
The septa are so delicate and short that their extension inward can- 
not be observed. 
Towards the base of the specimen there is evidence of complete, 
upwardly arched, irregularly developed tabula. No other endothecal 
structures are to be seen. Unless more anterior tabule have been 
destroyed, the fo1m must have possessed a calyx of extraordinary depth. 
I have little doubt that these specimens represent a Rugose coral 
which should be ascribed to a new genus: the material, however, is much 
too imperfect to justify the erection of a genus at present. 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 339 S. Royal Ontario Museum of Palaeontology. 
1 Geol. Sur. Can., Palaeoz. Foss., Vol. III, pt. IV, p. 278, pl. XXIV, figs. 1 and Ia, 
1906. 
