258 The Ottawa Naturalist. [March 



longitudinal indications of linear septal markings are also not 

 unfrequently developed. Calyx of variable depth, in short, tur- 

 binate coralla comparatively shallow, often with broad margins, 

 in more cylindrical forms generally somewhat deeper in pro- 

 portion to the diameter and with steeper sides. Surface of calyx 

 blistered and often marked radially by interrupted, more or less 

 distinct, superficial septal ridges. Inner structure entirely vesi- 

 culose, composed of convex blister-like plates resting on each 

 other and directed obliquely outward and upward to the peri- 

 phery ; at the centre of the visceral chamber the vesicles are 

 more nearly horizontal and as a rule larger than the others. 



This species is very variable in shape and size, sometimes 

 in the stout, short forms reaching a diameter of over 10 cent, 

 with a length of about 27 cent, in the slender forms an equal 

 length may be attained' with a thickness of only 3 or 4 cent. 

 In his description of C. Senecaense Billings mentions a variation 

 in length of from three inches to two feet with a diameter of three- 

 quarters of an inch to one inch and a half The same authority 

 in referring to the size of C. grande says " There are fragments 

 of this species in the collection of the Geological Survey of 

 Canada, five inches in diameter ; and one specimen, still lying in 

 the rock, is known which is three feet long." 



Examples of twin corallites with a common epitheca are not 

 uncommon. 



Locality and formation. — Abundant in the Corniferous and 

 Hamilton formations of Ontario. 



1 



