STROMATOPOROIDEA. 



235 



differ from the types previously considered in the fact that the radial 

 pillars and concentric laminae are so combined with one another as 

 to lose their distinctness as separate elements, and to become fused 

 with one another so as to form a continuously reticulated skeleton. 

 Moreover, the skeletal tissue has a peculiar microscopic structure, 

 being minutely porous or tubulated (fig. 1 1 9, a and b). Definite 

 zooidal tubes are also present, and these are crossed by more or less 



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Fig. 119. — a, Tangential section of Strojuatopora Beutk.it, enlarged twelve times, showing the 

 reticulate skeleton and the porous skeleton-fibre ; b, Vertical section of the same, similarly en- 

 larged, showing the tabulate zooidal tubes ; c and d, Tangential and vertical sections of Strom- 

 atopora bucheliensis, similarly enlarged. Middle Devonian. (Original.) 



extensively developed transverse partitions or "tabulae" (fig. 119, 

 b and d). The type of this group is the genus Stromatopoi'a itself, 

 in which the ccenosteum is massive or laminar and is usually fur- 

 nished with an epitheca. The skeleton is completely reticulate, the 

 radial pillars and their connecting-processes being completely fused 

 with one another, so as to give rise to a vermiculate tissue traversed 

 by minute, irregular, tabulate zooidal tubes. Very commonly, the 



