422 Silurian and Devonian Fossils of Canada. 



and a-half lines. The transverse diaphragms are not visible in the 

 specimens examined. The walls of the separate corallites are 

 thick and concentrically wrinkled. 



One specimen with corallites two lines in diameter appears to 

 be a variety of this species. 



Formation and Locality. — Trenton. Blue Point, Lake St John. 



Collector. — J. Richardson. 



Genus Pal^eophyllum (Billings). 



Generic characters. — Corallum fasciculate or aggregate ; co- 

 rallites surrounded by a thick wall ; radiating septa extending the 

 whole length ; transverse diaphragms either none or rudimentary ; 

 increase by lateral budding. 



This genus only differs from Petraia or Streptelasma by form- 

 ing long fasciculate or aggregate masses instead of being sirnpie« 



Pal^eophyllum rugosum (Billings). 



Description. — Corallum in large aggregations of scarcely se- 

 parate corallites, which where they open out upon the surface of 

 the rock are from one to six lines in diameter, the average adult 

 size being about four lines. Radiating septa reaching the centre ; 

 about twenty-two septa in a corallite four lines in diameter, with 

 an equal number in a rudimentary state between. 



The great disparity in the size of the tubes in the same mass is 

 owing to the mode of increase and gradual growth of the young 

 corallites. These, of all sizes from one line in diameter and 

 upwards, are uniformly intermingled with the adult individuals. 



Formation and Locality. — Trenton. Lake St. John, Little 

 Discharge. 



' Collector. — J. Bichardson. 



Petraia rustica (Billings). 



Description. — Straight or slightly curved, covered with a strong 

 epitheca, which is more or less annulated with broad shallow 

 undulations ; radiating septa about one hundred or usually a little 

 more; much confused in the centre, where they form a vesicular 

 mass ; every alternate septum much smaller than the others, only 

 half the whole number reaching the centre. Length from two 

 inches and a half to three inches and a half. Diameter of cup 

 one inch to one inch and a half; depth of cup half an inch or 

 somewhat more. 



