6fi G. LINDSTEÖM, HELIOLITIDiE. 



during the normal state of the polypary has the appearance figured on pl. iv, f. 29, 

 assumes, when this peculiar modiiication of the constitution of the polyp sets in, a quite 

 different aspect as shown in pl. iv, figs. 27, 28, pl. v, figs. 1, 2. The whole arrangement 

 of the tubnli (lig. 27) becomes irregular, their dividing walls are sinuous and crooked, or 

 even dissolved between contiguous tubuli. On the inside of the walls they are covered 

 (fig. 28) with numerous, minute thorns and asperities. They increase in thickuess and 

 irregularity and are as unlike common tubuli of a Heliolites as possible. The tigs. 1 — 2, 

 pl. v represent the coenenchyma in this state. It is this change which is visible in the 

 middle of the longitudinal section pl. iv, fig. 30, where it forms a narrow fascia. The 

 septa also partake and lose their normal character, become sinuous, intertangled, coalescing, 

 but are always twelve (pl. iv, lig. 27). Sometimes, when the septa are much reduced, 

 the structure reminds of that of Hel. interstinctus in which, however, the characters are 

 constant. 



This species has been found in the shale beds b — c near Wisby, one specimen has 

 been brought up from a depth of 5 metres in the harbour of Wisby, detached from the 

 shale beds, which form the bottom there. 



Heliolites Liljevalli n. 



Pl. IV, figs. 32—34. 



Of this cui*ious and very distinct species only a single specimen has hitherto been 

 found. It is disciform with a thickness of 10 millims. The calicles attaiu scarcely one 

 millim. in diameter. The theca is stelliform, the angles facing the septa as deep as in Hel. 

 parvistella. The septa are long though not all of equal size and reach to the axis of the 

 calicle, which is excentric or a little on the side of the centre, whence the septa nearest 

 the lesser moiety of the calicle are shorter. The tahulce are highly irregular, oblique, wavy, 

 convex and they have on their superior surface rows of stout spines which chiefly are 

 visible in the longitudinal section (fig. 34), where also the septal laminte and their com- 

 position of oblique fibrill» are evident. The coenenchyma consists of the most minute tubuli 

 that exist in this genus. They are of irregular section, seldom polyedric, elongated, bent, 

 of varying size, though all very small. Their walls are thicker than in any of the other 

 species and the distantiated tabulaa are concave. But the most peculiar feature consists 

 in the numerous short ridges which project from the walls of the tubuli into their lumen, 

 generally one in each tube, in some as many as three. By growing they divide the tube 

 and through this fission forro one or more new coenenchymal tubes. But they may also 

 be present and continue almost through the whole length of the tube without initiating 

 any fission. In the longitudinal section fig. 34 they are seen in the tubes at left. What 

 is more stränge, they are also found in the two calicles represented in the transverse section 

 fig. 33, where they stretch in a loculus of each like a little adventitious septura. 



This species has been found in the stratum a, the »Red Stratum», near Wisby, which 

 has proved very rich in new and interesting forms. 



