1898-1902. No. 32.] FOSSIL FAUNAS FROM SERIES B. 13 



Parallelopora favositiformis iiov. gen. et sp. 

 PI. IV, fig. 3-4, pi. V, fig, 1-5. 



About one half of a colony of this intere.sting form is found in 

 ScHEi's mateiial. The general form is irregularly flat sub-hemispherical 

 with a greatest diameter of about 11 cm. and a greatest thickness of 

 about 4. 



By macroscopic examination the specimen will at once be taken 

 for an ordinary Favosites. On the surface we readily discern the 

 sections of the fairly regular, mostly pentagonal or hexagonal coi'allites 

 and in longitudinal fractures numerous tabulae. The diameter of the cells 

 is on an average 1 mm., and the number of tabulae in one mm. gener- 

 ally 1-2. 



In microscopic sections however, we at once find that the form shows 

 a character that is not found in any true Favosites. In a tangential 

 section we commonly see at the junctions of the thick walls of 

 different corallites the section of a circular cell or tube, 

 developed in the wall itself, which at these places curves regularly around 

 the tube. It has the appearance of a section of a thick walled cylindei-, 

 the walls of which run out into the straight ordinary walls of the large 

 polygonal corallites. 



The diameter of the circular cells is about 0,2 mm. and varies very little. 

 I have succeeded in obtaining longitudinal sections of these tubes and they 

 are found to run as narrow, generally slightly curved, cells parallel or sub- 

 parallel to the ordinary large ones. On account of their small diameter we 

 never find them running through the whole section, one or both ends are 

 closed by the slightly converging walls, but I have no doubt that they run 

 through as well as the large cells. The fact that seen in tangential section 

 they always show nearly Ihe same size indicates their true cylindrical 

 form. What distinguishes these small tubes from the large ones, in 

 addition to their form and small, regular size, is the fact that they never 

 show any tabulae. The tabulae of the neighbouring cells never enter 

 these small ones. From this fact we may conclude that the cylindrical 

 tubes represent something qiute different from the large cells and cannot 

 for instance be regarded as embryonal stages of the latter. They un- 

 doubtedly had a function of this own. 



In the Ordovician North American form Columnopora cribriformis 

 Nicholson observed small circular or oval cells situated-chiefly at the junc- 

 tions of the cell- walls — imbedded in the wall. These "intramural canals" 

 may probably be anatomically and biologically related to the cylindrical 



