114 G. LINDSTRÖM, HELIOLITIDiE. 



often is the case. The calicles are sunk a little in the coenenchyma, the twelve septa 

 nan'ow, tapering, reaching halfways to the centre; broadly bifurcated or forming a net 

 at their basis. The theca which links them together is visible oiily as continuations from 

 their bases and can not be discerned as an independant sceletal element further down in 

 transverse sections. The septa form laminte which have the same conformation of oblique 

 baculi as in Coccoseris. The central area is covered by pointed papilla3, which in a longi- 

 tudinal section are seen to be the tops of irregular or sinuous baculi completely filling 

 the centre of the calicle. 



The coenenchyma, as seen on the sui^face, is composed of narrow tubes, the walls 

 of which are provided with small spines on the sides. These walls are relatively thick 

 and increase in thickness lower down in the coenenchyma so as to entirely fill up the 

 tubes (pl. XI, f. 33) and, as seen, are formed like large broad baculi. 



It occurs in detached pieces along the shores near Wisby probably mostly derived 

 from the oldest stratum of Gotland a. It has also been found in ska at östbjörka in 

 Dalecarlia in the whitish limestone with Leptajna Schmidti, thus from the top of the Lower 

 Silurian. In Estland it seems to bee common in the corresponding strata F"^ — i^^ at 

 Worms, Hohenholm in Dagö, at Piersal from which places Academiker Fe. Schmidt kindly 

 has sent me specimens named Heliolites inordinatus. 



Through the kindness of Professor Fr. Frecii I have been enabled to examine the 

 original specimen of Ferd. Roemer's »Heliolites interstincta», which is preserved in the 

 University Museum at Breslau. I have given a figure of a portion of its surface on pl. 

 XI, fig. 35 and I have found that it in all particulars agrees with other specimens of this 

 Acantholithus. 



The Museum of Breslau also possesses six specimens of an Acantholithus from 

 Sadewitz bearing the name Heliolites asteriscus F. Roemer. Of these three belong to the 

 species above described, and are identical with the Gotland specimens as well as with the 

 »Heliol. interstincta» just mentioned and preserved in the same museum and these all are 

 consequently to bear the specific name »asteriscus» by which F. Roemer designated the identic 

 Sadewitz fossils. Two other specimens belong to an Acantholithus which probably is to form 

 a new species, and the sixth specimen is a variety of Acanthol. lateseptatus above described. 



On plate xii, figs. 1 — 2 an underterminated specimen of an Acantholithus has been 

 delineated. It has been found in a single fragment on the shore near Wisby, and is 

 probably derived from the Arachnophyllum stratum a. It seems in a certain way to be 

 intermediate between the two other species. It has grown in thin lamellas, connected with 

 each other, the uppermost with a thickness of 8 millimeters. The calicles nearly of one 

 millimeter across. The septa are longer than in the two preceding species and the central 

 area consequently not so wide nor the papillte so numerous. The calicular tube shows 

 in a longitudinal section on both sides the septa of the structure peculiar to the Coccoseridas 

 and the centre filled with the narrow contorted baculi. The coenenchyraal tubes are 

 distinct, with thick walls and continue downwards provided with distantiated concave 

 tabulfe. The epitheca does not attain the thickness as in Acantholithus lateseptatus and 

 is in a section seen as a finely serrated line. 



