new G&nus of Devoniayi Corals. 897 



specimens. Sometimes the entire specimen maj be in the 

 above condition, and may consist of several superposed 

 colonies ; in other cases the specimen may consist of one 

 (sometimes more than one) colony in this condition, and of 

 one or more colonies in the following state. 



(B.) In a second group of specimens the axes of the visceral 

 chambers are represented by dark lines, from which proceed 

 slender also dark radii, the walls of the corallites being at the 

 same time more or less completely obliterated, the septal spines 

 being no longer recognizable, and the tabulae having almost 

 or quite disappeared. Specimens in this condition can be 

 readily recognized by the possession of a characteristic dark- 

 brown or black colour on broken surfaces, together with the 

 possession of a crystalline texture and an almost conchoidal 

 fracture. 



Tangential sections of such examples (PI. XVI. fio-. 2) 

 show appearances which are at first sight very similar to what 

 is seen in corresponding sections of Stromatoporoids belonging 

 to the genus Actinostroma^ Nich. The general ground-mass 

 of the section is, however, composed of a translucent struc- 

 tureless or obscurely fibrous horn-like material, of a brown 

 colour, not clearly exhibiting the walls of the corallites, and 

 showing no light spaces filled with calcite, such as would 

 represent the cavities of the tubes. The section, on the other 

 hand, exhibits a number of dark stars, usually with six rays 

 each, and these stars become united regularly by the union of 

 their rays, so as to give rise to a kind of " hexactinellid " 

 structure. The centre of each of these dark stars represents! 

 as will be seen, the centre of a visceral chamber, and each 

 star therefore corresponds with a single corallite. 



Vertical sections of specimens belonging to the group now 

 under consideration present the same translucent, horn-like 

 brown aspect (PL XVI. fig. 1 c, or the upper half of fig. 6). 

 The most conspicuous feature in such sections is the presence 

 of parallel vertical dark lines, which look like the walls of the 

 corallites, but which really represent the axes of the visceral 

 chambers. Midway between each pair of these dark lines we 

 may often recognize much fainter lines, which indicate the 

 position of the true loalls of the corallites. The entire ground- 

 mass of the section has more or less conspicuously a charac- 

 teristic fibrous or semicrystalline aspect ; and we may here 

 and there recognize the position of one of the tabulai (PI. XVI 

 fig. Ic, i). 



The appearances just described were regarded by Professor 

 Schliiter as being of an organic nature, and he hence referred 

 the group of specimens here in question to a new genus and 



