CCELENTERATA : LITERATURE. 185 



Kugosa, these seeming to have filled the place now taken by the scleroder- 

 mic Zoantharia. Until quite recently it was believed that all the Rngosa 

 were Palaeozoic, with the exception of the genus Holocystis, represented in 

 the Cretaceous period (Lower Greensand) by the single species H. elegans. 

 Recent researches, however, have brought to light the existence in our 

 present seas of at least two genera {Haplophyllia and Gtiynia), which be- 

 long-to the Rugose family of the Cyathaxonidce ; and certain Tertiary 

 Rugose Corals (Conosmilid) have also been described (Martin Duncan). 

 Of the families of the Rugosa, the Cyathophyllida and Cystiphyllida are 

 exclusively Palaeozoic ; the Cyathaxonida are Palaeozoic, but are represented 

 by two living genera; and the Stauridte are represented in the Silurian 

 rocks (StaTiria), Devonian {Metriophyllum}, Permian {Polyccclia\ and in 

 Tertiary deposits (Conosmilia). 



The Zoantharia sclerodermata, though attaining their maximum at the 

 present day, nevertheless are well represented in past time, beginning in 

 the Silurian period. The Perforata are principally represented by the 

 Favositidce during Palaeozoic time, though other forms of this section are 

 not unknown ; but, like the Afoi'osa, they attain a much greater develop- 

 ment in the Mesozoic and Kainozoic deposits. 



The Zoantharia sderobasica are hardly known as fossils, but the Miocene 

 deposits of Piedmont (Middle Tertiary) have yielded a species of Antipalhes. 



The Zoantharia malacodennata, 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. 



With the reference of the Helioporidce to the Alcyonaria, the range of 

 this order has been enormously increased in past time. Formerly no ex- 

 ample of the order was known as occurring in any Palaeozoic stratum, the 

 so-called Protovirgularia of the Lower Silurian being probably a Graptolite. 

 Now we know of various abundantly distributed Alcyonarian corals in the 

 Palaeozoic rocks, the most important being the Heliolites of the Silurian 

 and Devonian. The allied genus Polytremacis is Cretaceous. Of the 

 Gorgonidce two genera (Mopsea and Websteria) are found in the Eocene ; 

 and the genus Corallium, doubtfully quoted from the Jurassic and Creta- 

 ceous, is found in the Miocene, which has likewise yielded examples of his, 

 Gorgonia, &c. The Pennatulidce commence in the Eocene, with Graph- 

 ularia. The Tubiporidce (unless the Palaeozoic Syringoporida be referred 

 here) are unknown as fossils, and the Alcyonidce are not known to occur 

 till the Pliocene is reached. 



The Ctenophora, being wholly destitute of hard structures, are not known 

 at all as occurring in the fossil condition. 



LITERATURE. 

 GENERAL WORKS. 



1. " Manuel d'Actinologie et de Zoophytologie." De Blainville. 1834-37. 



2. " Klassen und Ordnungen des Thier-Reichs," vol. ii. ' Strahlenthiere.' 



Bronn. 1859-60. 



3. " Manual of the Coelenterata." Greene. 1861. 



4. "Essay towards a Natural History of Corallines." Ellis. 1775- 



5. "Die Pflanzen-Thiere in Abbildungen." Esper. 1788-1830. 



6. " Histoire des Animaux sans Vertebres," vol. ii. Lamarck. (Ed. 2, 



1836.) 



7. " History of British Zoophytes." Johnston. 1847. 



8. " Manual of Marine Zooloq-y for the British Isles." Gosse. 1855. 



