ON THK BEITISH FOSSIL CORALS. 129 



and their more or less horizontal and perfect tabulae, recall the Tubiporiuoc 

 amongst the order of the Alcyonaria. 



The Alcyonaria are Actinozoa which are separated by MM. Milne-Edwards 

 and Jules Haime from the Zoantharia on account of the pinnate structure of 

 the tentacles, and from these important organs being invariably eight in 

 number. 



The zoantharian tentacles, on the contrary, are simple or irregularly rami- 

 fied, and increase in number with age. 



The Alcyonaria are divided into the families of the Alcyonidee, the Gorge- 

 nidae, and the Pennatulidae. 



The first two families have an adherent corallum, and the last consists of 

 free forms. 



The Alcyonidae have no hard central axis, but this characterizes the 

 Gorgonidffi. 



Now the Cornularinse, Telestingg, and Alcyoninas, subfamilies of the Alcy- 

 nidae, are clearly allied to the Tubiporina; by their soft structures ; but the 

 hard external structures of this subfamily are only faintly shown in the spi- 

 culate scoi'iaceous conditions of the external tegument of NejjJithy a, Spoggodes, 

 and Paralcyonium. The polypes oi JSfejjMii/a and Paralcyonium enter their 

 spiculate and dense external covering when they contract; but the hard 

 structures of S^oggodes celosia, Lesson, are very slightly developed. 



TuBiPOEA (pars), Linnaeus. 



Tuhipora, Lamarck. 



The genus has been examined by MM. Milne-Edwards and Jules Haime 

 with their usual care and acumen. 



The specimens of Tuhipora are so common that the descriptions of these 

 authors concerning the hard parts of the corallum can readily be followed. 



The coraUitcs are formed principally by a tabular waU, the tissue of which 

 is calcareous and readily fractured. There are no septa, but there are ru- 

 dimentary tabulas, which cut off the visceral cavity into more or less perfect 

 stages. The corallites arc cylindrical, and usually attain an equal height ; 

 but they do not touch each other, for they are united by a peritheca, which 

 is only seen here and there in distinct floors. The budding takes place 

 from the connecting peritheca, which is therefore a true coenenchyma, and 

 not like that of Solenastrcea. Were the corallites in contact the appearance 

 of Chcetefes would be presented ; so that the presence of the coenenchyma is 

 the differentiating structure. It is only of generic value, and thus there is ' 

 a very strong reason for associating the Chsetetinee and all the other fossils 

 with long tubular structures, no septa, and tabulae with the Alcyonidae in the 

 subfamily Tubiporinse and near the genus Tubijjora. These retaarks are ■ 

 subject, of course, to the consideration whether the views of Agassiz already 

 noticed are correct. 



Keuss's genus Styhphyllum (Gosau Chalk) cannot be associated with the 

 Alcyonidee, for the species has septa. The corallites are united by their 

 walls without there being a coenenchyma, and tlie walls are imperforate. The 

 junction of the corallites takes place by means of an epitheca. 



The junction may occur at any part of the corallito. 



The resemblance of StyhphyUum to some of the Halysitinte (Ed. & H.)* 

 necessitates an examination of their structural peculiarities. 



* Op. cit, vol. iii. p. 286. 

 1871. K 



