9(5 G. LINDSTRÖM, HELIOLITIDiE. 



each other, generally a little wavy and on their upper surface in some instances covered 

 with short, blunt spines. The coenenchyma is coraposed of irregular lamellaä forming a 

 tissue of large bladders. These lamella; are in a few places traversed by thick longitudinal 

 baculi, which stånd out on the surface as small rounded nodules pl. ix, f. 40. 



Exactly on the same plan the specimens from the other localities are built, as may 

 be seen by the figures. The only difference lies in the size and proximity of the calicles 

 and the shape of the polypary. In all the size of the calicles is nearly half that of the 

 Anticosti specimens and in the specimens from Borenshult the calicles are nearly contiguous 

 leaving very little space for the coenenchyma. The shape of their polypary is almost 

 spha3rical, in some instances pyriform. The English specimens (fig. 43) are a little altered 

 and the septal ridges have acquired an irregular aspect. 



More deviating is the specimen from Bara, Gotland, which has been delineated on 

 plate X, tigs. 3 — 5. It is a discoid polypary, with exsert calicular margins, ornated with 

 twelve thick, oviform nodules, and without other vestiges of septa than interiör longitudinal 

 ridges without spines. The tabul^ are rather concave. The coenenchyma is of the common 

 vesicular kind with short, thick rods scattered in it and the peculiar nodulose appearance 

 of the surface of the coenenchyma is caused by the protruding of these rods through the 

 coenenchymal lamellte. As this variety, which perhaps can be seen in the light of a 

 mutation, on the whole comes more near to this species than to any other, I have united 

 it with these forms. 



This species has the greatest affinities with a following species, the Lower Silurian 

 Pr. bacillifera, Avhich, however, has large septal spines and a greater number of larger bacilli 

 in the coenenchyma. 



Pr. speciosa is an exclusively Upper Silurian species being in Sweden found at 

 Borenshult in Östergötland, and at Bara backe in Gotland. Further at Dudley in England 

 and at the Junction cliff of Anticosti (in Billing's Middle Silurian). 



Propora compacta n. 

 Pl. X, figs. 6—7. 



1883. Hel. iuterstinctus LiNDSTR. Silurische Korallen nus Nord-Russland, p. 19. 



Polypary discoid with closely set calicles of a diameter of one mm. enclosed within 

 a thick theca, angularly bent in twelve short in- or outgoing points or angles, the interiör 

 ones having the character of short septa not visible in vertical sections. These angles 

 give both sides a fluted appearance. The tabulas are close, nearly horizontal or bent in 

 convex curves. 



The coenenchyma is of a mixed vesiculose-tubular character, consisting of thick 

 and long bacilli, which packed in the narrow intercalicinal spaces coarctate the dissepiments, 

 that have small dimensions, but the common convex form. By their proximity and great 

 number they give the frarae of the polypary an appearance of compactness. 



