74 G. LINDSTRÖM, HEI.IOLITIDiE. 



have »cloisons bien développées», and so forth. As to Lyellia there is oiily said that its 

 »murailles» are »épaisses et costulées», in all other respects it coincides with Propora and 

 scarcely not in that respect, as it is also stated that Propora has costse. For the rest 

 there are further down under the genus Camptolithus reasons adduced for not longer 

 retain LyelHa as an independant genus. I think, that if there wi^re no other differences 

 found between Propora and Pli)smopora than those adduced by Milne Edwards and Haime, 

 there is no great cause to keep them apart and this was also the reason why I formerly 

 united both under Plasniopora. But through låter researches I have seen that there are 

 actually differences of generic value. As to Plasmopora and Propora, having inany features 

 in cotnmon, there are still several points which are of value as distinction, thus for in- 

 stance, that in Plasmopora there are in the coenenchyma large vertical laminaj. In Propora 

 there is strictly only Propora tubulata with exsert calicles or with »bords saillants» and 

 in Plasmopora also some species are provided with exsert calicular margins. There are 

 Plasmopora?, some with long and others with nearly rudimentary septa, but the generic 

 distinction does not depend on this circumstance alone. 



The characters of the Plasmoporine genera, according to niy conception, are the 

 following. 



Gen. 1. riasmopora. M. Edw. & Haime. 



Calicles sui'roundcd by a stelliform space, formed by the continuation of the septa 

 outside the thcca and their union at the ends forming an area, callcd aureola. Coenen- 

 chyma of irregular, disconnected and interrupted tubuli, often changing into detached 

 bacilli or even acula^. Tiie traverses are horizontal dissepiments as well as irregular 

 convex lamina?, both sorts occuring in the same specimen. 



Gen. 2. Propora. M. Edw. & Haime. 



Calicles without costie or only very short ones, not forming an aureola. Septa 

 consisting only of fi'ce spines not forming ariy lamellas. 



Coenenchyma entirely consisting of vesicular tissue without tubuli, with unconnected 

 bacilli, baculi and aculaä. 



Gen. 3. Camptolithus n. gen. 



Tabulai of the calicle convex, commonly short and intermingled as to form a 

 vesicular tissue of small (;onvex lamelk-e, quite identical with that of the coenenchyma 

 and also provided with aculse and bacilli. 



Gen. 4. Dijyloepora. Quenstedt. 



Calicles of varying shape according to their stage of develoj)ment, with rows of 

 spines instead of septal laminaj. 



Coenenchyma of two different strata: the older and innermost vesicular, the younger 

 and exteriör of closely packed, straight baculi of a peculiar conformation. 



