64 G. LINDSTRÖM, HELIOLITIDiE. 



with that just described as occurring on the surface. This resernbles rather more what 

 obtaius in the other species of Heliolites. We find by this that there are several inodifica- 

 tions, even in the same species, of this mode of gemmation. 



There is also evidence of intracalicinal gemmation in this species, as represented in 

 tig. 15, pl. IV. The procedure seeras to have been the same as described above in Hel. 

 interstinctus, the median calicle being about to begin, the left one showing the next step 

 and the right one being further advanced. In the central calicle a narrow belt of coenen- 

 chyraa has been developed around the calicle. In the bottora of all these calicles, however, 

 the coenenchymal tissue is still ^'isible, and although not fuUy developed, they had already 

 begun to bud. 



This variety has been found chiefly in the shale beds (c) at Djupvik, Eksta, though 

 there may be some specimens from a few other localities as at Lilla Carlsö, with a ten- 

 dency to vary slightly towards the »intricatus»-type. 



Heliolites hirsutus n. 



Pl. XI, figs. 18—22. 



It forms semiglobose masses with circular, densely crowded calicles having a dia- 

 meter of 1,2 millimeters. The septa, as seen on the surface and in a transverse section, 

 (figs. 18 — 19) have the short form as in Hel. interstinctus. Bases of spines are, however, 

 observable as diminutive tubercles on their edge (fig. 18) and these are present in great 

 numbers intact in the longitudinal sections (fig. 20) where they nearly fill the calicular 

 tube, emanating from the narrow septal lamella and directed in a bow upwards and in- 

 wards, gradually tapering into a fine point. The thin tahulce are in consequence of the 

 numerous spines irregularly horizontal. 



The scarce coenenchyma has the appearance common amongst the Heliolitse though 

 not so regularly polyedric and nearly only in one single row between the calicles. In a 

 longitudinal section, owing to the preponderance of the calicles, it is difficult to find its 

 tubes, but (fig. 22) they are narrow with distantiated, horizontal tabuUe. A remarkable 

 feature, the same as observed in Proheliolites, is that a coenenchymal tube by degrees 

 widens, is invested with septal spines and in fact is metamorphosed into a true calicle 

 (fig. 22). This is a peculiar modification of the coenenchymal gemmation, as one coenen- 

 chymal tube is sufficient to perform this change. 



This species shows afiinities with Hel. Barrandei, but may be distinguished from it 

 through the scarce and irregular coenenchyma, through the shape of the calicles and the 

 spines, and moreover through its remarkable manner of budding. 



It has been found in detached boulders at Hulterstad in Öland by J. G. Andersson 

 and also at Skärlöf, the same island by Dr G. Holm. I have also had specimens from Worms, 

 Piersal (F^) and Hohenholm (Dagö) in Estland, Patakumäggi near Hapsal, Lyckholm, Kertel 

 in Dagö, and a fragment also from Sandö north of Gotland. It is confined to the upper- 

 most strata of the Lower Silurian of Sweden and Russia. 



