50 



G. LINDSTRÖM, HELIOLITID^. 



Heliolitidie. 



1. Coenenchyrna. 



2. Twelve regular, coherent septal lainellaj. 



3. Imperforate tlieca. 



4. Coenenchymal and /n</'rtcalycinal geiri- 



mation. 



5. Tabula? without fossula3. 



6. No epithecal covei"ings över the calicles, 



nor false opercula. 



7. Calicle preserving the same size during 



its lifetime. 



8. Theca having a microscopic structure of 



fibrilla3 directed obliquely upwards. 



Favositidaei. 



1. JS^o coenenchyrna. 



2. No coherent septal lamellit, oiily septal 



spines of irregular nuraber, 20 or 30, 

 never regularly twelve. 



3. Perforate theca with nuraeroiis oscula. 



4. 7n/ercalycinal geinmation. 



5. Tabuhe with fossula:'. 



6. Epithecal coverings and false opercula. 



7. Calicles increasing in size during con- 



tinued growth. 



8. Theca3 of minute threadlike vertical ele- 



ments. 



After a long and continued examination of numerous specimens I have come to the 

 conclusion that the fossil corals, which I of late have named Heliolites decipiens are 

 nothing else but a phase or moditication of the growth of Hel. interstinctus. A colony 

 of this may for a time grow quite regularly, sho^\■irlg the twelve septa as described above, 

 and then assume the appearance of decipiens. But there are also specimens where both 

 sorts of calicles may be found alongside on the same surface. In one specimen, where 

 the decipiens character predorainates, there are, as iigured pl. ii figs. 3 — Qa, few calicles 

 of which one, probably the youngest, has largc unequally developped septa, irregularly 

 curved, another tig. 4 where they are quite regular and equal, reaching far inwards, then 

 there is one, tig. 5, with septa in the regular interstinctus-fashion, and at last tig. 6 we 

 have the decipiens stage without the least traces of any septa. 



Having thus duly considered the value of the innumerable gradations in confor- 

 niation merging into each other, I cannot avoid the conclusion that Heliolites decipiens 

 must be united with H. interstinctus as a variety, or perhaps rather more properly 

 be regarded as a transient state in the growth, changing again into the typical shape. 

 But this moditication can also be stable a long while or during the whole existence of 

 the colony and thus gain a certain appearance of independant specitic value. It is ques- 

 tionable whether not other species than Hel. interstinctus may have had a »decipiens» 

 stage, depending on the reduction of the septa. So I have found from the Middle Devo- 

 nian of Eifel a large polyparium with calicles, in Avhich no septa are visible. This might 

 possibly be a transformation of Heliolites porosus. Pl. ii tig. 20. 



It must also be taken in consideration that a false appearance of a decipiens-stage 

 can originate in the interiör of all species through metamorphic changes in the fossilised 

 structures, of which Penecke has given good information. ' Close beside quite intact 



1 Ueber die Fauna . 

 1887 ]>. 267, Taf. XX f. 3. 



einiger paläozoischen Korallriffe der Ostalpeu, Zeitschr. deutsch. geol. Gesellsch. 



