KONGL. SV. VET. AKADEMIENS HANRLINGAE. BAND 32. N:0 I. 75 



I may here remark that Sardeson in his paper on the Tabulate Corals, p. 353, has 

 cstablislied a Family of PlasiaoporidsE in the Suborder Helioporidas and includes in it, 

 besides the two first above mentioned genera, also Pinacopora and Houghtonia. As to 

 Houghtoiiia it is synonymens and identical with Columnopora, which latter was ranged 

 by Sardeson with Michelinia as member of his new family Pleurodictyida?, but both are 

 synonyms and identical with Calapoecia, an older genus of Billings, which according to 

 the views I have represented above at page 24 has no connection with the Heliolitida?. 

 As to Pinacopora I cannot find it different from Propora, and it is probably only a variety 

 of the common species Pr. conferta. 



Plasinopora. Milne Edwards & Haime. 



1839. Porites p. p. LONSDALE. Sil. Sysi, p. 687. 



1849. Plnsmopora MiLNB Edw. & H. Comptes Rendiis, forne XXIX, p. 2G2. 



1850. Asti-feopora d'Orbisny. Prodr. I, p. 50. 



1851. Palreopora Mac Coy. Brit. Palseoz. Foss., p. 17. 



I some time, adhering too closely to the distinctive characters given by Milne 

 Edwards and Haime in their fundamental works, held the opinion that the corals belonging 

 to the genera Propora and Plasmopora could not be generically kept apart, but must be 

 joined in a common genus, Plasmopora, to be retained as being the oldest. But since I 

 have been able to examine a richer material of specimens I have found that both genera 

 are very well distinguished from each other. 



Plasmopora is well separated from all other genera by the following peculiarity. 

 The calicle proper is surrounded by a more or less stelliform space or area, formed by 

 the twelve prolongations of the septa which stretch outside the theca of the calicle and 

 enclose longitudinal compartments and unite with each other through a curved lamina at 

 the ends. This distinctive area, which is found in all species of this genus, I have called 

 an aureola. A good specimen of it is to be seen on plate xi, fig. 36 and others. If the 

 calicles are closely set, the aureola cannot expand as much as else and those of neigh- 

 bouring calicles intermingle. 



The septa are either coherent laraelli'e of fibrous texture Avith spiny margins or, as 

 it were, broken up, neaiiy entirely, in oblique, strong spines. The coenenchyma has 

 irregular tubes, they are crooked and bent, their walls are discontinuous or the traverses 

 mingle from different tubes. The traverses can be regularly horizontal, funnelshaped or 

 obliquel}' intercrossing and besides in the same specimen the convex lamellas can exist 

 alongside with the former. The aculte are present together with bacilli and it can actually 

 be observed (pl. vii, fig. 10), how the latter have been formed out of the former. Coenen- 

 cliymal gemmation has been observed in two species. From the septa and the aureolar radii 

 being simple or barbed, from the different interna! structure specific characters may be 

 obtained. 



