52 ft. LINDSTRÖM, HELIOLITID^.. 



From the Arachnophyllum stratum near Wisbj^ there is a variety, growing in disks 

 of the vertical thickness of 25 mra. The calicles are small, circular, distant, 4 — 5 railliras 

 apart and 0,5 mm. in diameter. The abundant coenenchyma is very finely reticulated, 

 with tubuli of regular sixsided shape. 



There are in all at least five variations. 



1. Interiör side of the theca quite smooth and small calicles. 



2. Quite smooth inside, calicles lai'ge, densely placed. From the Ohliesaare pank 

 in Ösel I have seen a variety between 1 and 2 in the Museum of Reval. 



3. Small indentations in the theca, calicles small, much distantiated from each other. 



4. Large calicles, closely set, indications of septa, coenenchyma partly irregular. 

 To this belongs Heliol. bohemieus of Wentzel. I cannot but find that it is onlj' a 

 variety of interstinctus or intermediate between this and the genuine decipiens. I have 

 had Bohemian specimens for examination. Wentzel admits in his description the great 

 variability in size and in the thickness of the theca. The chief difference from decipiens 

 lies according to him in »das Coenenchym ist sehr unregelmässig ausgebildet». The size 

 of the calicles is of no account at all as specitic chara,cter, as in many instances has been 

 shown, that the same surface bears calicles of greatly deviating size. Moreover, I have 

 specimens presenting on one side the »bohemieus» featiu^e, on the other side the regular 

 interstinctus coenenchyma. This variety also occurs at Taggamois, Undwa, stratum I of 

 the Island of Ösel. 



5. Large calicles, closely set, indications of septa and regular coenenchyma. To 

 this variety belongs the Eiflian specimens, mentioned above. All these tive varieties have 

 been found in the Gotland strata. I have also received specimens from Chicago by Dr 

 Head, from Louisville Kentucky, named Hel. subtubulatus and even Plasmopora follis, 

 from Ta-pa-shan, Schenzi China by Baron Richthofen. In Sweden it also occurs in 

 Norderön, Jemtland and the »Riks Museum» is in possession of specimen from the upper- 

 silurian of Öfveds kloster in Scania. Sorae calicular tubes attained a great length, one 

 holding 56 millim. all along with or breadth of 2 mm. 



Much on account of the pretended affinity with Mac Coy's Fistulipora and still 

 more through a false appearance of coenenchyma in such genera as Callopora, Dybowskiella, 

 etc. a supposition of affinity between these and the Heliolitidte lias been most positively 

 maintained by several authors, especially by Dybowski, Waagen, Neumayr and with some 

 hesitation also by Nicholson. Here is not tlie place to enter into any lengthened discus- 

 sion upon this point, as it will require a most detailed research of longer dnration of 

 time than I now can dispose of, nor is it at present much need of it, sincc of late several 

 authors, as for instance Rominger, James, Ulrich, Sampson and Gregory, have definitely 

 ranged amongst the bryozoa nearly all those fossil species ^vhich the former insisted upon 

 to regard as corals. 



The principal questionable forms have been referred to Monticnlipora, Callopora, 

 Fistulipora and so forth. But there prevails a great confusion as to the limits and names 

 of seve]'al of theui. What Waagex has called Dvbowskiella is Lichenalia for the American 



