CCELENTEKATA : ACTINOZOA. 119 



species (viz. H. elegans, from the Lower Greensand). In the 

 lower Palaeozoic Bocks the Rugosa are especially abundant ; 

 but in the Permian formation the order is represented by the 

 single genus Polycodia. 



The Zoantharia Sclerodertnata, though attaining their maxi- 

 mum at the present day, nevertheless are well represented 

 in past time, beginning in the Silurian period. One subdi- 

 vision of this group, the Tubulosa, is entirely confined to the 

 Palaeozoic Rocks, and another, the Tabulate, is chiefly Palaeozoic. 

 The Perforata and Aporosa, on the other hand, are more abun- 

 dant in the Mesozoic and Kainozoic Epochs. 



The Zoantharia Sclerobasica are hardly known as fossils, but 

 the Miocene deposits of Piedmont (Middle Tertiary) have 

 yielded a species of Antipatlies. 



The Zoantharia Malacodermata, from the soft nature of their 

 bodies, are obviously incapable of leaving any traces of their 

 existence ; though we are by no means therefore justified in 

 asserting that they did not exist in past geological epochs. 



The Alcyonaria are very doubtfully represented in rocks older 

 than the Chalk ; the Lower Silurian fossil, called Protovirgu- 

 laria, being more probably referable to the Hydrozoa. One of 

 the Pennatulidce (viz. Graphularia) has been found in the Lon- 

 don Clay (Eocene), and the same formation has likewise 

 yielded two species of Gorgonidce (Mopsea and Websteria). 

 The genus Corallium has likewise been found in deposits of 

 Miocene age. 



The CteMophora, being entirely destitute of any hard 

 structures, are not known at all as occurring in the fossil 

 condition. 



APPENDIX GIVING A TABULAR VIEW OF THE DIVISIONS OF THE ZOANTHARIA 

 SCLERODERMATA AND RUGOSA (AFTER MILNE-EDWARDS AND JULES HAIME). 



A. The Zoantharia Sclerodermata are defined by the possession of a 

 sclerodermic corallum, the parts of which are arranged in multiples of 

 five or six. Septa generally well developed, but not combined, as a rule, 

 with tabulae. 



The following chief divisions of the Zoantharia Sclerodermata are, with 

 few alterations, those adopted by the above mentioned authorities : 



I. TABULATA. Septa rudimentary or absent ; tabulae well developed, di- 

 viding the visceral chamber into a series of stories. 



1. Thecid<e. Corallum massive; a dense spurious ccenenchyma formed 



by the lateral union of the septa ; tabulae numerous. 



2. Favositidce. Septa and corallites distinct; little or no true ccenen- 



chyma. 



3. Seriatoporida. Corallum arborescent; sclerenchyma abundant and 



compact ; tabulae few. 



4. Milleporidte. Corallum massive or foliaceous; septa not numerous; 



sclerenchyma tabular or cellular. 



