112 COELENTERATA—CNIDARIA CLASS IT 
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 daminae, 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 
Millepora ; 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 (Mfillepora), 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 (/eaae- 
tinellida) ; and Salter to 
ee ee ee 5 the calcareous sponges, 
Actinostromu interteatum, Nich. Silurian (Wenlock); Shropshire. A, Tan- +s 
vential section showing radial pillars and reticulated structure of concentric whose example Nichol- 
laminae. B, Vertical section, showing formation of laminae out of processes ale 
siven off horizontally by radial pillars, 12/; (after Nicholson). s 2 n also follow ed. 
Lindstrém, Carter, and 
Steinmann subsequently pointed out their relations to Hydractinia and Mille- 
pora ; and Nicholson and Murie now regard them as constituting an independent 
group of extinct Hydrozoans allied to Hydractinia on the one hand (Actinostro- 
midae), and Milleporu on the other (Stromatoporidae and Idiostromidae). 
Actinostroma, Nich. (Fig. 197). Skeleton haviag 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. 4. clathratwm, Nich. 
( = Stromatopora concentrica, pp., Goldt.) 
Clathrodictyon, 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 zodidal tubes are sparsely 
distributed. Plentiful in Devonian ; less common in Silurian. 

Fic. 197. 
