KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 11 



2. The veslcnlai- coenenchyina is proper to the corals of the tribe Plasmoporina^ 

 and is coniposed oi" a great nuraber of thin, convex lamelhi3, equivalent to the horizoutal 

 traverses or dissepiments of Heliolites. Through coveriiig each other nearly as tiles 

 they enclose an empty loculum below themselves and these locula become large or dwind- 

 ling to inicroscopical littleness aecording to the rauch varying size of the lauielJfe. In this 

 same way a tissue is formed which also is common for so raany corals belonging to widely 

 different families or without any relation or affinity, as for instance Galaxea and Cysti- 

 phylluni. In its siniplest and purest condition it appears in tlie genus Propora in sucli 

 species as Pr. conferta (Pl. ix fig. 12, 18) and var. minima (Pl. ix fig. 24). Now, in others, 

 there have arisen accessories of the vertical element, which are entirely wanting in the 

 Proporaj just cited. In Propora tubulata, for instance, (Pl. viii fig. 14) or still better in 

 Plasmop. scita (Pl. vii lig. 8, 11) diminutive, vertical stylets sit on the superior surface 

 of the convex laniellaj. I propose for them the term acnlsei derived from acnia, a little 

 needle. No doubt they cover the whole surface, as can be learnt from the transverse 

 sections (Pl. viii lig. 12, 15) and the same are also scattered on the surface of the 

 convex lamellas in Pl. viii fig. 8, 11, though looking more blunt, like wartlets, perhaps 

 through weathering or not having gro\vn out. They can be very irregularly distributed 

 as in section pl. viii fig. 19, often wanting and then reappearing. In Plasmopora? reti- 

 culata pl. vu fig. 36 they are no longer ffee and without connexion with each other, they 

 have combined and form a reticulate web (fig. 35) giving the surface of the coral very 

 rauch the appearance of the tubular coenenchyma. By this combination they have 

 originated short tubuli intermingled with the convex laminas. 



These aculte again are arranged in another fashion, having grown in longitudinal 

 rows or series following exactly in the same line above each other as seen in Pl. vii fig. 10. 

 There they are still ^vithout connection in a longitudinal direction, but in another specimen 

 of the same species a junction is attained and the convex laminae of the coenenchyma 

 are, as it were, pierced by narrow rods or rather thecal elements, which somewhat disturb 

 the formation or regular growth of the convex lamella? that nevertheless tend to main- 

 tain their regular shape though they are pressed in between these rods and in shape 

 approach the Heliolitidan horizontal tabute. What these strings really are, becomes evident 

 on inspection of transverse sections as in pl. vii fig. 7, 9. They form a coenenchyma 

 of irregular tubes, which, however, do not continue downwards, but ai'e interrupted. 

 Further modifications of this kind of coenenchyma, somewhat related to that of Heliolites, 

 are described in detail under the different species of Plasmopora. It onl}^ rests to signify 

 a coenenchyma! formation peculiar to this genus. Around the calicle (Pl. xi fig. 36, 37) 

 is placed an ai-ea formed of twelve radii or costtTs, as they also may be named as they 

 are a direct continuation of the septa, outside the calicular theca, and it might be said that 

 the whole is a sort of reduplication of the calicle as these radii are linked together at 

 their exteriör ends through a sort of theca, being composed of angular lines of the verti- 

 cal element which continue nearly uninterrupted downwards and in a longitudinal section are 

 seen to encircle the calicular tube on all sides as a zone, broader than the irregular coenenchy- 

 mal tube. I propose to call this fine structure aureola, which is entirely wanting in the other 

 genera of the Plasmoporinaj. It may he somewhat difficult to find it so clear and evident in 



