42 LINDSTRÖM, A SPECIES OF TETRADIUM FROM BEEREN EILAND. 



scattered fragments of crinoidal stems. On account of the bad 

 State of preservation of these fossils it was not possible to make out 

 any sufficiently good characters whereupon to ascertain to wliat 

 particular group of tliis large genus Actinoceras the Orthoceratite 

 might pertain and thus to fix its stratigraphical place. There are 

 no exteriör distinctive characters to be gathered from ornaments of 

 the shell and the position of the sipho was not recognisable as the 

 specimens are crushed and flattened. Moreover the longitudinal 

 sections of the species of Actinoceras are nearly alike from all 

 formations where they occur, ranging as they do from the middle 

 of the Lower Silurian up in the Trias. It would indeed have 

 been quite irnpossible to ascertain the geological age of these 

 fragmentary fossils had not at last a most characteristic one 

 turned up, which gave the certainty wished for. 



This fossil, which I am now going to describe, is a species 

 of the genus Tetradium Dana (not of Fr. Schmidt) of which ge- 

 nus four or five species or varieties have been described by Ame- 

 rican authors. They are at once distinguished from other fossil 

 corals or bryozoa through the peculiar form of their square tu- 

 bulär openings with four short so called pseudo-septa ärran ged 

 in two pairs, opposite each other, giving the regulär appearance like 

 the form of än ornament in the gothic architecture, which is called 

 diaper, in german »Vierpass». Most of the species known have 

 grown in compact masses, the tubes or zoooecia in close contact, 

 but the Beeren Eiland specimens form a loosely coherent, rather 

 spongy mäss, the tubes having grown isolated, only united late- 

 rally through horizontal tubuli or stolons in the same manner as 

 the Syringoporse with which corals they thus have a slight re- 

 semblance. Seen from the superior surface again there is some- 

 thing reminding of Halysites in the chains of coherent tubes, as 

 shown in the subjoined figures. 



