131 



regularly pinnate or simply ramified ;- 

 the following characters : — 



-these two orders having 



Cnidaibia. 



having 

 tentacula 



' simple or ramified irregularly, and 1 Order 

 in a variable number. / Zoantharia. 



regularly pinnate, and invariably of) Order 

 the number eight. J Alcyonaria. 



The order Zoanthakia is sub-divided into three sub-orders, 

 according to the nature of the integument. This may be — 

 1 st, permanently completely soft ; 2nd, transformed into a 

 sclerenchymatous tissue, and constituting a true Polypary ; or 

 3rd, it may be provided with spiculse, and forming by means of 

 an epithelic tissue a central stem. 



ZOANTHARIA 



of ■which 



the 



integument 



' is soft and never forming a scleren- 

 chmatous or epithelic Polypary. 



is solidified by calcareous salts so as 

 to form a Polypary. 



contains calcareous spiculse, and pro- ' 

 duces a sclerobasic tissue, which 

 forms a solid stem in the axis of 

 the Polypary. 



Z. Malacoderma 



or ACTINIARIA. 



Z. Scleroderma 

 or Madreporaria. 



Z. Caulicula 



or 

 Alcyonaria. 



B. Stratigraphical Distribution of Fossil Corals. 



SiLTTEiAN Corals. 



The Silurian strata of the British Islands admit of the 

 following: subdivision: — 



Upper 

 Silurian 



Tilestone and Upper Ludlow rocks 



Aymestry Limestone 



Lower Ludlow rocks 



Wenlock Limestone 



"Wenlock shale 



Woolhope Limestone and shale 



Denbighshire Sandstone and shale 



Tarannon shale 



Ludlow series 



Wenlock series 



