68 G. LINDSTRÖM, HELIOLITID^. 



Gen. Cosmiolithus n. gen. 

 (Kccpov, ornament.) 



Coenenchyma composed of a iiiedley of small and largei" tubuli of circular section, 

 tlie former surrounding the larger ones. Their walls are very thick and the lumen is narrow 

 with scarce, concave or oblique tabulaj. The calicles have a complete set of perfect, narrow 

 septa, somewhat irregularly sinuous and in the centre, where they meet, forming a reticular 

 tissue with open meshes. Owing to the great development of the septa, the tabulse are 

 seen only as small horizontal lines betvveen them. The septal lamellaj are contiuous in 

 their whole length and consist of fibrillse. Both species hitherto known have grown in 

 thin lameliar expansions. 



From the genus Heliolites, to which it is most nearly related, it differs through its 

 peculiar coenenchyma and the uncommonly thick coenenchymal walls. In respect to the 

 septa and their arrangement it has a great resemblance with Hel. parvistella, but their 

 structure is upon the whole different. What upon the first glance distinguishes this genus 

 is the uncommonly narrow tubuli of the coenenchyma, the largest of which do not attain 

 more than 0,i millimeter in width. 



Cosmiolithus ornatus n. sp. 



Plate V, figs. 4—11. 



The polypary lias grown in thin incrusting lamelte, scarcely attaining two millims. 

 in thickness, bearing calicles only on the superior surface, the inferior being covered 

 with a concentrically wrinkled epitheca. In a section this epitheca (fig. 10) shows a peculiar 

 lobate appearance, being comparatively more corrugated than the smoother epitheca in 

 other Heliolitidse. 



The calicles attain only 0,5 mm:s in diameter and their edge is incised by the angles 

 facing the septa and filled with minute tubuli of the coenenchyma. 



The septa in the calicle proper are well developed, straight, narrow, thickening 

 downwai"ds and form in the centre a reticulated tissue where they meet and, as it were, 

 intertwine with each other. This central reticulation is tubular and in a longitudinal 

 section its tubes cannot as to their structure be discerned from the larger coenenchymal 

 tubuli, it is only by their position in the middle of the calycinal section they are 

 recognized. The tabulse are around the central reticulation of the calicle curved in a 

 small bow upwards and continue more horizontal within the central tubes of the calicle. 



The coenenchyma consists of two sets of rounded tubuli, f. 7, one more than four times 

 as large as the other, which surrounds the larger one. Both are very tiny, the larger 

 attaining a diameter of 0,i millim., the smaller only of 0,02 millims. Deeper down below the 

 surface, as seen in sections, f. 8, they have much thicker walls than could be appreciated 

 from the surface, and they are filled with rather scarce, concave tabulas, f. 10. Their walls, as 



