KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 1. 29 



Tetradiiim, Dana. Nicholson^ says that Tetradium presents a very striking resem- 

 blance to Heliolites in the form of the septa, which he considers as pseudosepta. On 

 the same account many other corals, not so dubious as Tetradium, might also be classed 

 as allies to Heliolites. 



Bouene ^ says that Tetradium minus resembles Heliolites in the »close approxima- 

 tion of its corallites, in the possession of tabute» and the pseudosepta. I cannot find 

 that there is the least resemblance between these two genera in the position of the »corallites» 

 (? = calicles), as in Heliolites the calicles are more or less distantiated through the inter- 

 vening coenenchyma, in Tetradium, on the contary, the calicles are entirely contiguous 

 without the least traces of any coenenchyma. The »possession of tabute» is a character 

 Avhich is shared by such a diversity of not else allied corals that it is of no value at all 

 for pointing out any affinity between those two genera and the same is also the case 

 with the septa. The regularity and the constancy of the twelve septa in Heliolites in 

 contradistinction with the characteristic four septa in Tetradium must moreover exclude 

 all ideas of any affinity between them. 



Thecia, Goldfdss. As to the pretended affinity of this genus with Heliolites it may 

 be enough to remind that the calicles have no interiör theca and are confluent with each 

 other, communicating through an abundant system of horizontal tubes lying in conse- 

 cutive series above each other, in a longitudinal section giving the appearance as of 

 oscula, like those in the walls of Favosites. The septa are irregular and of a varying 

 number. The tabute are thin and scarce, sometimes arranged like those of Cystiphyllum, 

 in a few instances regular. Consequently I cannot consider Thecia as a member of the 

 Heliolitidse. 



Thecostegites, Edw. & H. Having lately through the kindness of M. D. Oehleet 

 been enabled so examine specimens of Thec. Bouchardi E. H., I have found that I formerly 

 was mistaken in supposing its affinity with the Heliolitidas (Ann. Mag. Nat. Hist. 1876, 

 vol. H, p. 16). It has tabute as the Syringoporaj and a few tubelike connections be- 

 tween the calicles; the calicles are in many instances closed with a pseudooperculum as 

 in several Favositse and the connecting »plateaus? are not of the nature of a coenenchj^ma. 



The now revised genera being, on reasons alleged, eliminated from the close affinity 

 of the Heliolitidas, this faraily consequently retains of the previously known genera only 

 the following ones, viz. 



Heliolites, Dana. 



Plasmopora, Milne Edw. & Haime. 



Propora, LoNSD. 



Diploöpora, Quenstedt. 



Lyellia, M. E. & H. (if it really is an independent genus). 



Further I have appended the family of the Coccoserida? to the Heliolitidaj as nearly 

 related on account of their regular and consimilar septal formation, their mode of 



1 Tabulate Corals p. 234. 



2 Heliopora p. 469. 



K. Sv. Vet. Akad. Handl, Band 32. N;o 1. 



