40 



LINDSTRÖM, HELIOLITID^Ti. 



iiophylluin stratum (a) of Gotland they are concave. The dissepiinent of the coeneii- 

 chyma is also composed of regular, though mnch raore densely crowded tabulie. 



The gemmation has been observed to be of two difterent kinds viz. 1. Ccx^nen- 

 cliymal and '2. Intmealicinal, both as deseribed above at p. 19, 22. Sonie differences of 

 a specific nature are rnentioned beloAv under the species. 



Very small polyparies, affixed to other corals or shells, consisting of an initial poly- 

 pierite and a few, three or four, which have sprouted from it, testify to the development 

 out of ova. The young, of necessity free swimming larva or further developed young 

 polyp had fixed itself and secreted the wormlike tube, the first beginning of the poly- 

 pary as stated more in detail above. 



The geological distribution of the species of this genus, which are deseribed below, 

 is seen from the next table. 



Heliolites interstinctns L 



var. decipiens Mac Coy 



Hel. porösas Goldfuss 



Hel. Barrandei Penecke 



var. spongodes n 



Hel. parvistella Ferd. Eoemee . . . 



Hel. parvistclla-intricatns 



Hel. fasciatus n 



Hel. repletus n 



Hel. Liljevalli u 



Hel. hirsutus n 



Lower 

 Silurian. 



Upper- 

 most 

 beds. 



Upper Silurian. 



5 B 



o 

 Vt 



Ludlow. 



Devonian. 



x\s here shown this genus at first appears, though scantily represented, in the uppei'- 

 most beds of the Lower Silurian, from the Lepta?na limestone of Dalecarlia in Sweden, 

 and in the detached limestone blocks at Sadewitz in Silesia, which seera to be derived 

 from the »Lj^ckholmer Schicht» of Estonia and also in these. It occurs in great richness 

 of varieties and specimens in the Upper Silurian of Sweden, England, Russia, Bohemia, 

 North-America, China and Austvalia and continues through the Lower Devonian to the 

 lower division of the Upper Devonian, as mentioned above at p. 31, after which time it 

 seems to have become extinct. It is found in the Devonian strata of Russia, Austria, 

 Germany, Italy, France and England. 



One species, Hel. Barrandei, is common to both the tapper Silurian and Devonian 

 formations and the same is probably the case with Hel. interstinctus. 



