CYATHOPHYLLOIDEA. 289 



composed of comparatively large vesicles. In the reduction of the ex- 

 ternal vesicular zone and the proportionate development of the central 

 tabulate area, the Devonian and Carboniferous genus Campophyllum 

 closely resembles Omphyma, and also approaches the Zaphrentoids. The 

 genus further resembles these latter, and differs from Omphyma, in the 

 possession of a single very large fossula, giving rise to a conspicuous 

 bilaterality of the corallum. 



Family 2. Heliophyllidce. — The members of this family agree in 

 many respects with the typical Cyathophyllidcz, but are markedly 

 distinguished from these by the characters of the septa. These 

 structures in the present family are thin, and are composed essen- 

 tially of nothing more than the primordial septal plate, occasionally 

 with a thin coating of stereoplasma towards their bases. The septa 

 are thickened on their sides by conspicuous lamellar ridges (rep- 

 resenting the septal spines of such forms as Pholidophyllum), 

 which are directed obliquely inwards and upwards from the exterior 

 of the visceral chamber towards the centre of the same, and which 



Fig. 168. — Structure of the corallum of Heliophyttum elegautuhim, from the Devonian (Ham- 

 ilton Group) of North America. A, Transverse section, enlarged nearly twice ; B, Longitudinal 

 section of the same, taken just below the calice, similarly enlarged. h, Cardinal septum, in the 

 fossula ; g, Counter septum ; e, Peripheral vesicular zone ; t, Central -tabulate area ; r, Oblique 

 septal ridges (" carinal ridges ") on the sides of the septa. (Original.) 



form a marked feature in longitudinal sections of the corallum (fig. 

 168, b). In transverse sections of the corallum (fig. 168, a) these 

 oblique septal ridges appear as conspicuous cross-bars or " carinas, " 1 

 which run transversely to the septal laminae and produce a most char- 

 acteristic appearance. On the free edges of the septa, again, the 

 septal ridges appear as prominent transverse ridges or teeth. Owing 

 to the development of the septal ridges just spoken of, the septal 



1 The appropriate name of "carinae" was given to these septal bars by Miss 

 Mary E. Holmes, M.A. 



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