PLATE I. 



Unless otherwise stated, all the figures are of natural size. 



Pycnostylus GrUELPHENSis (page 3). 



Figure 1. Portion of a hand specimen, shewing a natural longitudinal 

 section of some of the corallites. 

 " la. An isolated corallite of this species, which has divided above 

 into four branches, two of which (c c) are broken oflf at their 



" 16. Piece of a natural transverse section of the corallites, shewing 

 their quadripartite and more rarely tripartite division sub- 

 sequent to gemmation. 



Pycnostylus elegans (page 4). 



Figure 2. Anterior end of a corallite of this species, showing its calycinal 

 gemmation and ribbed outer surface. 

 " 2a. Natural longitudinal section of a portion of a corallite, exhibiting 

 the complete tabulae and marginal septa. 



