KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 61 



At present it must be left undecided whether the following names belong to this 

 species or not. 



1860. Hel. interstinctus ElCHWALD. Lethfea rossica I, I, p. 453. His description »12 lames vertioales pénétrant 



jusqu'au centre» shows that his specimen cannot be H. interstinctus, but possibly 

 belongs to this species. 



1876. Hel. interstincta ROMINGER. Corals of Michigan, p. 12, pl. 1, fig. 1. 



1885. » » Ferd. Roemer. Lethsea erratioa, p. 78, Tab. V, tig. 7. 



1885. Hel. raegastoraa Davis. Kentucky Corals, pl. 1, fig. 1. 



1885. Hel. interstinctus ID. Ibid., pl. I, fig. 4. 



Mode of groioth. The polyparium is discoid or lameliar, the larger polyparia with 

 protuberances from the superior or calicle bearing surface, no doubt originated through 

 the intracalicular geinination. These lamella? are often very thin, having a vertical 

 thickness of only three or four millimeters. The epitheca is iinely wrinkled and glossy. 



The calicles are at widest 2 milliras. The theca forms outgoing angles between the 

 loculi and ingoing angles opposite the septa, in consequence of what the whole assumes 

 the shape of a står and the outline of the calicle more or less deviates from the circular. 



The septa are long, stretching in some specimens quite to the centre of the calicle, in 

 others forming in the centre an irregular network by combining, as it were, with their ends. 

 In the former calicles (pl. iii, figs. 28, 30, and pl. iv, fig. 2) there is also at the meeting of 

 the septa an indication of the same reticulation through the curving and interlacing of their 

 ends. Sometimes they are longitudinally bent in zigzag and with small spinules on the sides. 

 In consequence of their meeting with their interiör edges in the central axis of the calicular 

 tube and because they there coalesce witl) each other no marginal spines have room 

 for developing. For the same reason the tahulce have rather the character of a dissepiment 

 and they are not stretching in coherent lamella; uninterrupted över the whole calicle, but 

 are subdivided in the loculi and bent a little upwards or even downwards or as a convex 

 lamella (figs. 29, 31, pl. iii). Owing to this subdividing of the tabula^ in the loculi and 

 to the prominence of the septal lamina in a longitudinal section it is very difiicult in 

 such a section to distinguish the calicular tube from the surrounding coenenchymal tubuli. 

 In these, however, the dissepimental laminas are most regularly horizontal. For the rest 

 these tubes are regularly polygonal with very thin walls. 



In many sections (figs. 3, 9, pl. iv) there is si-en a very distinct difference in colour 

 between the septa or longitudinal walls and the dissepiments or tabute, the former having 

 in transmitted light a paler, nearly strawcolour and the latter being dark or black. 



On the plates iii and iv specimens from different localities have been figured to be 

 compared with the original specimen of Feed. Roemer (pl. iii, f. 28). There is a specimen 

 from the Upper Silurian of Oesel (pl. iii, f. 30), one from Louisville in America (pl. iv, 

 f. 2), one from Kozcl in Bohemia (pl. iv, f. 5) and one from the Upper Silurian of Got- 

 land (pl. IV, fig. 8). In respect to their structure, as revealed in longitudinal sections, 

 there reigns the most complete conformity. Again in viewing the calicles on the surface 

 or in a transverse section there seems at first to exist a great dissimilarity between them 



K. Sv. Vet. Akad. Handl. Band 32. N:o 1. 8 



