266 



ZOANTHARIA. 



briefest way. In the genus Turbinolia itself (fig. 141), the corallum is 

 simple and conical, with a projecting styliform columella, but without 

 pali. The costas are very prominent, and the spaces 

 between them are marked with rows of small dim- 

 ples, which look like perforations in the wall, but do 

 not really penetrate to the visceral chamber. The 

 genus is well represented in the Lower Tertiary 

 deposits, but is doubtfully recent. In Smilotrochus 

 and its allies there is no columella, and pali are 

 rarely present. The type-genus is Cretaceous and 

 Tertiary. The genus Flabellum is the type of 

 another group of the family, and is distinguished 

 by the compressed and wedge-shaped form of the 

 corallum, the calice thus assuming an oval form. 

 The structure of the wall and septa in Flabellum 

 is peculiar, but is not so different from that of the 

 same parts in certain fossil corals of other groups 

 as to justify the removal of the genus from its pres- 

 ent position. The species of Flabellum are all 

 Tertiary and Recent. In Placotrochus and its allies 

 a columella of a lamellar form is present, and there 

 are rarely pali. The genus is Recent and Tertiary, 

 as also is the related genus Sphenotrochus. The 

 genus Trochocyalhus is the type of an extensive 

 series of forms, in which there is a fasciculate col- 

 umella, and generally one or more cycles of pali. 

 Trochocyalhus itself (including Thecocyathus) dates 

 from the Lias, and ranges to the present day. Al- 

 lied to this is the well-known genus Caryophyllia 

 (figs. 140 and 126), which ranges from the Creta- 

 ceous period to the present day, and is distinguished 

 by its possession of a trabecular columella and a 

 single crown of pali (fig. 128, a). 



The remaining types included in the Turbinolidoz 

 are more or less abnormal. The genus Dasmz'a, for 

 example, is so peculiar, that it has been regarded 

 as the type of a separate family {Pseudoturbinolidce), 

 the distinctive feature being that the septa are ar- 

 ranged in groups of three, in such a way that each 

 septum might be regarded as formed by the coalescence of three ele- 

 ments. The genus is Cretaceous and Tertiary. The Recent genera 

 Guynia and Haplophyllia, again, are remarkable in the fact that the 

 symmetry of the corallum is tetrameral, and they thus serve to lead us to 

 such ancient types as the Cyalhaxonice of the Carboniferous rocks. In 

 the true Cyalhaxonice (as typified by the Cyathaxonia cornu of the Moun- 

 tain Limestone) the corallum is simple and conical, the septa having a 

 tetrameral symmetry, and a " fossula " being present. There is a promi- 

 nent columella, and the interseptal loculi appear to be free from endo- 

 thecal structures. As the presence of a fossula, and the fact that the 

 septa have a tetrameral arrangement, cannot be considered as dis- 

 tinctive features, there would not appear to be sufficient ground for 

 excluding this genus from the Aporosa. The Silurian corals which have 

 been included in the genus Cyathaxonia belong, however, to the genus 

 Lindslrce?nia, which may also be referable to this division of the Madre- 

 poraria, though it will be here provisionally placed among the Rugosa. 



Fig. 141. — Turbinolia 

 sulcata. The upper figure 

 shows the exterior of the 

 theca with the costse. 

 The lower figure shows 

 the calice, with the col- 

 umella and primary and 

 secondary septa. Eo- 

 cene. 



