KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 32. N:0 I. 113 



AcanthoUthus lateseptatus u. 

 Pl. xn, figs. 23—30. 



This coral has the form of a large, expanded lamella with undulating surface; it 

 is verv thin, only 5 millims. in thickness with a surface of the dimensions of 18 X 12 cm. 



The basal or epithecal stratum is of uncomraon shape and thickness. Instead of 

 the usual, in a section scarcely perceptible film, there is here a well discernible tubular 

 stratum. In the figures 29 — 30 it is seen below the other sclei-enchyma. In the fig. 28 

 its lower surface is delineated with the apertures of the tiny tubes and in fig. 29 the 

 upper surface, the stellate markings of which possibly may be derived from parasitic, 

 boring organisms. 



The calicles are regularly distributed över the superior surface of the coral with a 

 mean distance of 2 millims., having themselves a diameter of a little more than one 

 millimeter. The septa (fig. 23) are short, triangulär, broad and covered with small warts. 

 The central area is large, studded with small, rounded papillas. The interiör of the 

 calicular tubes (fig. 29) is in the centre filled with baculi, on the sides of which there 

 are concave tabulte. In another section (f. 30) of the same specimen the tabulas are 

 wanting and only baculi are seen. 



The coenenchyma is composed of closely set, minute, irregularly polygonal tubes, 

 having in their aperture several short, blunt spines eraanating fi'om the interiör side and on 

 the crest of the walls also erect, warty prominences project. In a longitudinal section the 

 walls have increased considerably in thickness and the tubes are divided in compartments 

 by some few, distantiated, concave tabulse. In another section of the same specimen 

 (fig. 30) the baculi, of which the coenenchymal walls are constructed, have grown so as 

 to form a uniform mäss in which there is no vestige of any tube nor of tabuhc. It is 

 very difficult to make these intrinsic structural differences to agree -with each other. It 

 may be that an excessive growth of the coenenchymal walls in some speciraens entirely 

 suppress the formation of tabula?, leaving no place for these to develop. 



A large and fine specimen, belonging to the Geological Survey of Sweden, has been 

 found in a morainic accumulation at Kopparsvik near Wisby, probably like so many others, 

 of Lower Silurian origin. In the Stockholm museum there is also a specimen found on 

 the shore, Norderstrand, near Wisby. As stated on the next page a variety or mutation 

 of this species, now in the University Museum of Breslau has been found at Sadewitz. 



AcanthoUthus asteriscus. Ferd. Roem. p. p. 



Pl. XI, figs. 31—35. 



1858. Heliolites inordinata Fr. Schmidt p. p. Archiv, p. 226. 



1861. Heliolites interstincta Ferd. Eoemer. Sadewitz, p. 24, pl. IV, f. i. 



1880. Heliol. intricatus vav. lamellosus, LlJfDSTR. p. p. apud ÅNGELIN, Fragmenta Silurica, p. 32, tab. I, fig. 5. 



1883. Hel. asteriscus Ferd. Roemer p. p. Lethsea geognostica, Abth. 1, Lief. 2, p. 505. 



Corallum forming thin plates of about four millimeters in thicknes. The epitheca 

 is free, unless where growing out from or being in continuation with an older colony as 



