322 



ZOANTHARIA. 



agree with those of Michelinia in being vesicular or " cystoid " in 

 structure. The increase of the corallum is by basal gemmation, or by 



budding from the hollow 

 periodic expansions in 

 the intervals between 

 the old cups. In the 

 mode of increase, Chono- 

 stegites resembles Sy- 

 ri?tgopora, and the hol- 

 low periodic floors may 

 be considered as homo- 

 logous with the hollow 

 connecting-tubes of the 

 latter. On the other 

 hand, in the possession 

 of vesicular tabulae and 

 in the presence of mural 

 pores in parts where the 

 corallites touch each 

 other, the genus closely 

 approaches to Micheli- 

 nia. Nearly related to 

 Chonostegites is the Or- 

 dovician and Silurian 

 genus Syringofthyllum, 

 and we may also place 

 here the Devonian genus 

 Thecostegites. In both 

 these genera the coral- 

 lum consists essentially 

 of cylindrical, tabulate 

 corallites which are 

 placed in connection 

 with one another by 

 hollow, periodically pro- 

 duced, laminar floors, 

 into which the endothe- 

 cal tissues of the polypes 

 are directly continued ; 

 but in some cases these 

 floors are successively 

 superimposed on one 

 another, and give rise 

 by their union to a kind 

 of spurious ccenenchy- 

 ma. The structure of 

 the skeleton in these 

 genera is, however, too 

 complex to allow of its 

 being advantageously 

 considered here. 



Family 6. Thecidce. — This family includes only the aberrant genus 

 Thecia, 1 the structure of which is too complex to permit of more than 



1 As the result of extended investigations, the writer has been led to materially 

 modify the views which he formerly expressed (' Palaeozoic Tabulate Corals') as 



Fig. 208. — a, Part of a longitudinal section of Syringopora 

 reticulata, Goldf., from the Carboniferous Limestone of 

 Kendal, Westmorland, enlarged five times, showing the spini- 

 form septa and the funnel-shaped tabulae with their central 

 tube. Owing to the flexures of the corallites, the section cuts 

 the tubes in different parts, sometimes passing close to the 

 wall and showing the cut ends of the spiniform septa, some- 

 times passing through the axis of the visceral chamber and 

 bisecting the axial tube, and sometimes cutting the axial tube 

 and its enveloping tabulse in an oblique manner, b, Part of 

 a transverse section of the same specimen, enlarged five times, 

 showing the spiniform septa, and the cut edges of the tabula? 

 surrounding the central tube. (Original.) 



