112 



COELENTERATA CNIDAEIA 



CLASS II 



wrinkled epitheca, while the apertures for the emission of the polyps are 

 situated on the upper surface. The general tissue of the coenosteum is com- 

 posed of numerous, concentric, undulating, calcareous layers or laminae, which 

 are separated by narrower or wider interlaminar spaces, but are at the same 

 time connected by numerous vertical rods (radial pillars). The pillars as well 

 as the laminae are traversed, as a rule, by minute, irregularly directed canaliculi. 

 In some genera the coenosteum is provided with vertical tabulate tubes, 

 which most probably served for the reception of the polyps, as in the genus 

 Millqwra ; but in many instances they are wanting. The surfaces of the 

 laminae typically exhibit pores and small tubercles, and frequently also shallow 

 stellate furrows (astrorhizae), which radiate outwards from numerous centres. 

 Sometimes the laminae consist merely of a loose network of horizontal calcareous 

 fibres. 



Goldfuss at first held the Stromatoporoids occurring so profusely in the 

 Eifel for corals (Millepora), and subsequently for sponge-like zoophytes ; while 



von Rosen considered 

 them as horny sponges 

 that had become 

 secondarily calcified. 

 Sandberger and F. 

 Roemer assigned them 

 to the Bryozoans; 

 Dawson to the Foram- 

 inifera ; Sollas to the 

 silicious sponges (Hexac- 

 tinellida) ; and Salter to 

 the calcareous sponges, 



Fid. 197. 

 Actinostroma intertextuin, Nich. Silurian (Wenlock) ; Shropshire. A, Tan- 



gential section showing radial pillars and reticulated structure of concentric whoSO example Nichol- 

 laminae. B, Vertical section, showing formation of laminae out of processes rv 1 ^ ^ Pf-Jl^-nrQ^ 

 given off horizontally by radial pillars, 12/1 (after Nicholson). 



Lindstrom, Carter, and 



Steinmann subsequently pointed out their relations to Hydradinia and Mille- 

 pora ; and Nicholson and Murie now regard them as constituting an independent 

 group of extinct Hydrozoans allied to Hydradinia on the one hand (Adinostro- 

 midae), and Milkpora on the other (Stromatoporidae and Idiostromidae). 



Adinostroma, Nich. (Fig. 197). Skeleton having vertical or radial pillars 

 disposed at tolerably regular intervals, and extending continuously through all 

 or at least a considerable number of laminae ; in vertical sections, accordingly, 

 exhibiting a quadrate meshwork. The laminae consist of an anastomosing 

 network of calcareous fibres, generally having a porous structure ; their surfaces 

 are covered with projecting granules or tubercles, which represent the free 

 upper ends of the vertical pillars. Rare in Silurian, but very abundant in 

 Devonian of the Eifel, England, and North America. A. dathratum, Nich. 

 ( = Stromatopora concentrica, pp., Goldf.) 



Clathrodidyon, Nich. Like the preceding, but with radial pillars extending 

 only between the upper and lower surfaces of successive laminae. Characteristic 

 of Silurian ; rare in Devonian. 



Stromatopora, Goldf. emend. Nich. (Pachystroma, Nich. and Murie), (Fig. 

 198). Radial pillars uniting with the thick concentric strata or latilaminae to 

 form a finely reticulated tissue, in which tabulate zooidal tubes are sparsely 

 distributed. Plentiful in Devonian : less common in Silurian. 



