44 G. LINDSTRÖM, HELIOLITID^. 



Epitheca. In the disciform polyparies there is an extremely thin, in a seetion 

 scarcely perceptible lilin, transversaly wrinkled and longitudinally finely striated. In thc 

 branching and globular polyparies there is of course not much of an epitheca. It there nevor 

 forms a coherent covering on the surface, it occurs only in narrow irregular stripes for- 

 raing zones, as it were, between the calicles. It must be the common, coenenchymal 

 tissue which has secreted this fragmentary epitheca, probably at intervals when the living 

 surface of the coral had retired within narrower boundaries and the surface outside it 

 was dead. It must be borne in mind that this epitheca is the common exteriör wall of 

 all polypierites, corresponding to the simple wall which envelops the first or initial and 

 single polypierite, from which the other have budded. It is an araplification from this 

 secreted by a multiplicity of individuals placed along the borders of the polypary. 



The calide. The range of variability in regard to the size and the proxiraity 

 of the calicles is very wide. The diameter ranges from 3 mms to 1 mm. or a little 

 less. In length one and the same calicular tube has been found to reach a length 

 of 15 mms and probably was still 10 mms longer as it was hidden in its lowest 

 part. Those found in the youngest strata, the limestone beds signed as / — g — /(, have in 

 the rule the largest calicles, closely set and consequently a scanty coenenchyma. They 

 are very sballow, generally only 0,5 mm. deep and consequently the living animal tissue 

 cannot have been of any considerable thickness. 



Septa. The circular margin of the area is often slightly exsert and, what is most 

 characteristic, wrinkled with twelve short ingoing angles, in fact the twelve septa 

 which continue downwards into the calicular tube as faintly prominent, straight ridges, 

 so that the interiör side assumes a fluted appearance. In some more perfect specimens 

 the septa form extremely thin and short lamellas with. entire margin. In others again 

 they are nearly evanescent so as to approach to the variety called Hel. decipiens, which 

 actually, as will be shown further on, is nothing but a peculiar manner of growth of 

 H. interstinctus. As Peneckk observed in his H. Barrandei that the septa have dis- 

 appeared in deeper situated portions of the polypary may also be seen in Hel. inter- 

 stinctus, as for instance in the peculiar specimen drawn Pl. i fig. 20 of which fig. 24, a 

 seetion deeper down, exhibits quite empty calicles. This change is no doubt usually 

 due to the fossilisation, but it may there also sometimes have been an original defect of 

 septa. In some specimens as in one from the lowest beds there are in the youngest areas 

 longer septa which låter are shortened. 



Columella. The centre of the calicles is almost without exception provided with a 

 columellar protuberance of a variable shape, styliform, lameliar, straight or bent so as to 

 form an angular lamella. (See pl. i tigs. 9, 11, 12, 13, 14, 15, 20.) It ma)' he branching 

 (f. 14, 20) and occupy a larger space. As to its origin the figures 11 and 13 may give some 

 explanation. In the specimen, fig. 11, which evidently is a calicle not quite mature, the 

 septa on the right are longer than those at left, which are of the ordinary size. One of 

 the lefthand septa reaches to the centre and as a continuation of it and in coniiexion 

 with it lies the columella, also united wxih. two other septa. In fig. 13 an earlier stage 

 of development is represented. There are twelve septa of which a couple, lowest down, 

 still show the vestiges of their origin out of the coenenchyma. They are else all large 



