242 TABULATE CORALS. 



The visceral cavities of the polypes are also crossed by com- 

 plete, more or less horizontal tabulae. The smaller corallites 

 are typically provided with distinct walls, which may, however, 

 be rudimentary ; and they have their internal cavities intersected 

 by horizontal or strongly convex tabulae, while septa are en- 

 tirely wanting. No lateral channels exist in any of the fossil 

 forms (so far as known), by which the visceral cavities of the 

 larger corallites are placed in communication with one another, 

 or with the cavities of the smaller corallites. 



From the researches of Mr Moseley (Phil. Trans., vol. 

 clxvi p. 92, 1876), we know that Heliolites and its allies are 

 essentially similar as regards the structure of the corallum to 

 the living Heliopora, and we have therefore the right to con- 

 clude that this resemblance extended to the soft parts as well. 

 We have therefore every right to conclude that Heliolites and 

 its relations were Alcyonarian Zoophytes, with polypes of two 

 different kinds, the fully-developed zooids inhabiting the larger 

 tubes of the skeleton, and having eight mesenteries and eight 

 pinnately-fringed tentacles ; while the septa do not correspond 

 in number with the mesenteries, and are consequently to be 

 regarded as " pseudo-septa." The only important point in 

 which Heliolites and the forms related to it appear to differ 

 from Heliopora is that the cavities of the small sexless zooids 

 of the latter genus are stated by Mr Moseley to communicate 

 directly with the body-cavities of the larger corallites ; but we 

 have in the meanwhile no evidence of the existence in the 

 extinct genera of any apertures in the walls of the larger 

 corallites by which such a communication could be effected. 

 This difference, if ultimately established, will be one of great 

 importance ; but a further examination of the fossil forms will 

 be required to prove conclusively that the large zooids pos- 

 sessed no direct communication with the smaller ones. 



The genera included in this family are the Palaeozoic 1 Helio- 



1 The Devonian genus Battersbyia, E. and H. (Pol. Foss. des Terr. Pal., p. 227), 

 originally placed by its founders in the neighbourhood of Heliolites, has been shown 

 by Professor Martin Duncan (Phil. Trans., vol. clvii., 1867) to be a member of the 

 special family of the Palastrceacz, an extinct group of the Zoantharia Aporosa. 



