FOSSIL ACTING ZO A. 



481 



Actinozoa. The allies of the sea anemones are grouped into three 

 orders, named ZOANTHARIA, KUGOSA, and ALCYONARIA. 



Alcyonarians are composite, and have the pinnate tentacles in 

 multiples of four ; they are represented by the living Alcyonium, 

 which occurs fossil in the Red Crag. The sea pens are represented 

 by Graphularia in the London clay ; arid Pavonaria in the Chalk. 

 The Gorgonias are chiefly of Tertiary age ; but the living Isis is found 

 in the Cretaceous rocks. The Maestricht beds yield Moltlda ; and the 

 living Mopsea is first found in the London clay. The living genus 

 Corallum dates from the Jurassic rocks. In this order of late years 

 have been placed many genera of the 

 Primary period, among which may be 

 named Aulopora, Syringopora, rang- 

 ing from Cambrian to Carboniferous, 

 Halysites, Theda, Lyellia, Propora 

 of the Silurian, Helioiites^ and Plas- 

 mopora of the Silurian and Devonian, 

 and the Devonian Thecostegites. The 

 living genus Heliopora dates from 

 the Cretaceous rocks, where it is as- 

 sociated with Stylophyllum, Professor 

 Duncan suggests that the Favositidae, and many of the corals formerly 

 grouped with the Tabulata, belong to this type. 



Rugosa is an extinct group of corals, confined to the Primary rocks. 

 The septa are in multiples of four ; and this is expressed in Haeckel's 

 name for the group, Tetracoralla. The vertical septa are combined with 

 transverse tabulae ; frequently one of the principal septa is undeveloped, 

 and a fossette exists in its place. The corallites of the compound coral 

 are never connected by true ccenenchyma, being often connected by 

 their septa or their walls, or they may be connected by lateral processes. 



The larger number of corals referred to this group belong to the 



Fig. 88. Heliolites. 



Fig. 89. Strombodes. 



Fig. go.Cystiphyllum. 



Lower Primary Rocks, or Cambrian and Silurian periods. Among 

 such are Duncanella, Acanthocydus, Calophyllum, Cyathophylloides, 



VOL. I. 2 H 



