90 G. LINDSTBÖM, HELIOLITID^. 



1892. Tropora tubulata Lebedeff. Obersil. Fauna des Timan, p. 14, pl. 1, fig. 4a — b — c (not iig. 3). It is 



not quite sure that this belongs to the said species, whicli cannot be decided by 

 thc iraperfect tigures and desoription. 



1894. Plasmopora tubulata Wbisseumel p. p. Korallen der Silurgeschiebe Ostpreussens..., p. 668. 



1896. Propora tubulata SAEDESON. Tabulaten, p. 278, figs. 15—17. 



The oldest. denomination of this species is that given by Angelin in 1838, but as 

 it is only a name without desoription in a coUection of fossils, it is more appropriate to 

 keep that which has been so long in general use. 



Besides the above given synonyms there are several which in consequence of too 

 insufficient descriptions and figures must, until nearer notion be gained, remain doubtful. 

 Such are Propora tubulata Eichwald 1860, Leth. rossica, I, i, p. 455 seems to be a 

 Lower Silurian species. de Koningk, Fossiles palasoz. N. Galles du Sud, p. 23, gives only 

 the narae of this species. Also in F. Roemer's Sadewitz, p. 22, Tab. iv, f. 3 where the 

 figure 3 shows a coral much deviating froin the typical by Milne Edwards & Haime. 

 The same species in Nicholson, Tabulate Corals, pl. ii, f. 3, 36 can not be identical, as 

 it does not show any vestiges of septal spines. Quenstedt's figure in Petref. Deutschlands, 

 pl. 149, f. 12 does not show the characters. Malaise 1873 in Silurien du Centre de la 

 Belgique, p. 107 also enumerates Propora tubulatus (!). 



This common and as to its surface much variable coral opposes the greatest diffi- 

 culties to the endeavours to fix the distinctions between it and the closely simulating 

 Plasmopora scita. In both we find a great variability in respect to the shape of the 

 calicles, in the Pl. scita impossibility for the aureola to develop when the calicles are 

 densely crowded and again in the Propora no development of an aureola, even when there 

 is space enough between the calicles for such a development. There are great chances 

 of confounding both species with each other and it may thus happen that the one species 

 is current in scientific papers under the name of the other. And indeed when studying 

 a large number of specimens of both one is at a loss to decide to which species some 

 belong. Moreover the interiör structure, as studied in longitudinal sections, is often nearly 

 the same. At last it may perhaps be found that both are linked together through a series 

 of interinediate forms at the opposite ends of which stånd what we now call Plasmopora 

 scita and Propora tubulata. It cannot be denied that Plasmopora scita in spite of its aureola 

 has an interiör organisation which is more in concordance with that prevalent amongst 

 the Proporaj. It may, however, be borne in mind that the tendency to construe tubuli 

 is stronger in Pl. scita than in Propora. For the present it may be advisable to keep the 

 extreme forms separate and at least temporarily describe both as distinct species. 



The characters common to all varieties of this polymorphic species are the following. 

 The margin of the calicular theca is exsert and free above the coenenchyma and the diameter 

 of the calicles larger than in Plasmopora scita. There is no distinct aureola, even jn those 

 specimens whei'e the calicles are remote. The coenenchymatous, vesicular tissue is more 

 lax and composed of large bladders as in fig. 10, pl. viii. 



The typical surface, as represented by Milne Edwards and Haime in Brit. Foss. 

 Corals, pl. 59, fig. 2>a and of which I through the kindness of Prof. Alphonse Milne 

 Edwards have received a plaster cast, is figured anew on plate viii, fig. 4 from an 



