PLATE IV. 



Fig. 1 . — The central portion of the astrorhiza of Stromatopora ? dartingtonensis, 

 Cart. (= Stromatopora elegans, Carter), enlarged 12 times. Devonian, Teignmouth. 

 The specimen is a " reversed " one, the skeleton being replaced by transparent 

 calcite, and the cavities of the skeleton being opaque. 



Fig. 1 a. — The same restored, showing the skeleton opaque and the canal- 

 system filled with calcite, as is the case in ordinary specimens. [It is to be 

 remembered that the process of replacement, by which such " reversed " specimens 

 as the above are produced, is necessarily an imperfect process. Had the replacing 

 agent been silica, instead of calcite, the replacement might possibly have been 

 perfect. Hence in such a restoration of a "reversed" specimen as is here 

 attempted, the dark skeletal framework shown in the restoration can only be 

 regarded as giving the general form of the skeleton, and not as giving minute 

 structural details.] 



Fig. 2. — Stromatoporella eifeliensis, n. sp. ; portion of the surface of an en- 

 crusting specimen, showing the large astrorhizae, of the natural size. Devonian, 

 Gerolstein. 



Fig. 3. — Actinostroma stellulatum, n. sp. ; tangential section, enlarged 12 times, 

 showing one of the astrorhizge. Devonian, Teignmouth. 



Fig. 3 a. — Vertical section of another specimen of the same, similarly enlarged. 

 The section traverses one of the wall-less vertical canals connecting successive 

 astrorhizal systems. 



Fig. 4. — Distichopora coccinea, Gray (recent) ; tangential section, enlarged 

 24 times, showing the ccenosarcal canal-system, the gastropores (g), and the 

 dactylopores (d). 



Fig. 5. — Tangential section of the skeleton of a species of Millepora (M. 

 tortuosa, Dana ?), enlarged 24 times, showing the ccenosarcal canal-system, g, One 

 of the gastropores ; d, one of the dactylopores. 



Fig. 6. — Stromatoporella granulata, Nich. ; part of the surface of a specimen 

 from the Devonian rocks (Hamilton formation), Canada, enlarged about 6 times. 

 The figure shows a conical eminence, upon which opens one of the vertical astro- 

 rhizal canals, and from which radiate shallow superficial astrorhizal grooves, 

 formed by lines of elongated or vermiculate tubercles. Some of the larger 

 tubercles show at their summits the apertures of zooidal tubes ; and part of the 

 surface is covered with a smooth calcareous membrane, penetrated by minute 

 isolated circular perforations. 



