KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 32. N:0 I. 39 



another place says that it has been already employed as »Heliolithos varioruin autorura», 

 I have in vain made a search for these authors, but the naoie has indeed, written in 

 this inanner, a classical form and in accordance with such ancient mineralogical namcs 

 as Tecolithos, Hexacontalithos etc, which occur in Plinius Hist. Nat. Lib. 36, Cap. 19. 

 It seerns, however, that Guettard by some inadvertence left the true track and in his 

 Mémoires, vol. 2 p. 419 created the name »Heliolithes», »Heliolithe», for his new »Genre XV» 

 and thus imitated the many names ending on — ites, as hcematites and others, which 

 invariably are of the masculine gender, while those ending on — itis, being altogether 

 gems, are of the feminine gender. It would have been more convenient, if he had trans- 

 scribed Heliolithos into Heliolithus, as Plinius also uses similarly composed names for 

 minerals, as Ohrysolithus for instance. 



Now to change the old, often and universally employed word Heliolites^ and to 

 trän sf orm it to what it ought to have been, would cause too much confusion and might 

 certainly be approved by only very few, if an}^ authors. Consequently it is better to 

 keep it as it is. Again, on the contrary, for the new genera which may be created 

 within this family, it seems advisable to form their names according to the Plinian rules. 

 Thus, for instance, Acantholithus. 



The corals which belong to this genus generally have grown in diskshaped, flat or 

 slightly hemisph^rical polyparies, on the inferior or basal surface covered with a thin, 

 finely wrinkled epitheca. In some which are globular or slightly branching, calicles are 

 formed on all sides and consequently without any epitheca. 



The ' calicle has regular septa which sometimes have been eiitirely reduced so as 

 to give the interiör side of the theca a completely smooth surface. When ihej meet in 

 the centre they may form various sorts of network or even columellalike structures. A 

 little, transverse coluraellar protuberance often occurs in the middle of the calicle of 

 Hel. interstinctus. Commonly the septa in this genus are entire lamellte and not only 

 spinous projections from the theca, as in the Favositidaä or even in other Heliolitidse. 

 But in Hel. Barrandei the edges of these lamellas are serrated by long, curved spines. 



The coenenchyma is generally composed of regularly polygonal tubes, which multipl}? 

 through fission of their area by transverse sclerenchymatous partitions, that have developcd 

 across the aperture of a tube, from one wall to the other and thus dividing a tube into 

 two. Every tube is circumscribed by its own wall; hence the dividing ridge between 

 two adjoining tubes is a double wall. 



The intimate structure of their longitudinal walls is of the fibrous nature as des- 

 cribed abovc (p. 15) in the same way as the septa and the theca of the calicle, which 

 are coherent. There is some good evidence of a direct continuation or prolongation of 

 tlie septa out in the coenenchyma as is so manifest amongst the Plasmoporinte ; but 

 there is no sign of an aureola, though specimens of Hel. porosus may indicate some 

 approximation to it, as shown by Weisseumel's figure 3.~ The dissepiment of the calicles 

 consists of regularly horizontal tabulte; in some of the oldest specimens from the Arach- 



1 This name must be' written witliout h m accordauce with the other words eiidiug in ites, as not derivats 

 from liilios. 



^ Zeitschr. deutsch. geol. Gesellschaft 1898 p. 61. 



