i 3 2 TABULATE CORALS. 



favour of Alveolites, Lam. Lastly, Dr Rominger (Foss. Corals 

 of Michigan, p. 43) placed the genus in the Favositidce, in the 

 immediate neighbourhood of Alveolites, from which he regards 

 it as differing only by " more conical stout-walled tubes of less 

 compressed and more rounded form in the central or basal parts 

 of the polyparia." 



The true structure and affinities of Ccenites, Eichw., can be 

 determined with the greatest certainty by means of thin micro- 

 scopic sections ; and these show that the genus is not only not 

 Polyzoan in its relationships, but that it is in all respects pro- 

 perly referable to the Fdvo$itid& t standing upon the whole 

 nearer to Pachypora than to Alveolites. Thus, thin sections 

 show that the tubes are not only tabulate, but that they have 

 the more important feature of being placed in communication 

 with one another by means of a well-developed system of 

 " mural pores," which are precisely similar in all points of im- 

 portance to the pores of Favosites, and which only differ from 

 these in being irregularly distributed. Moreover, there is no 

 " c&nenchyma " present in the corals of this genus, as has been 

 generally supposed. On the contrary, the corallites (PI. VI., 

 fig. 5 a) are in close contact throughout their entire length, and 

 their walls are also everywhere quite distinct. In the centre 

 of the corallum the tubes have quite thin walls, and present 

 no feature by which they could be distinguished from the coral- 

 lites of a ramose Favosites. Just before reaching the surface, 

 however, each tube bends abruptly, often dividing at the same 

 time, and the wall for the rest of its course is immensely thick- 

 ened by a dense secondary deposit of sclerenchyma. In this 

 constriction of the visceral chamber near its mouth, the species 

 of Ccenites agree with those of Pachypora, Lindst. ; but in the 

 former the thickening is rigidly confined to a narrow external 

 band, and does not affect the internal parts of the corallum at 

 all ; whereas in Pachypora the thickening affects the tubes 

 throughout their entire length, and merely attains its maximum 

 as the mouth is approached. Furthermore, the corallites in 

 Pachypora are not markedly compressed or oblique, and are 



