neto Oenus of Devonian Corah. 399 



Fig. 6. Tangential section of an example of R. stromatopor aides, Eoem., 

 in wliich the visceral chambers and walls are nearly normal, 

 enlarged twelve times. The tubes are slightly below the average 

 size. Middle Devonian, Teignmouth. 



Fig. 6 a. Vertical section of the same, similarly enlarged. 



Fig. 7. Tangential section of a specimen of li. stromatoporoides, Roem., 

 in the normal condition, the tubes being of slightly larger than 

 average size, enlarged twelve times. Middle Devonian, Gerol- 

 stein. 



Fig. 7 «. Part of the same section, enlarged twenty times, and showing 

 the walls in a mineralized condition. 



Plate XVI. 



Fig. 1. Tangential section of jR. stromatoporoides, Roem., taken close to 

 the svuface of the specimen, enlarged twelve times. In part of 

 the section figm'ed the visceral cavities are filled with the 

 matrix, but in parts stellate crystallization has taken place, and 

 the walls and visceral chambers are largely obliterated. 



Fig. 1 a. Part of a tangential section of the same specimen, enlarged 

 twelve times. Owing to infiltration and crystallization the walls 

 of the tubes appear thickened and the visceral chambers are 

 partially obliterated. Curious rounded tubercles are also seen 

 at the angles of junction of the corallites. 



Fig. 1 h. Part of another slide of the same specimen, enlarged twenty 

 times. The tubes are partly fiUed with matrix and show dis- 

 tinct walls (sometimes with ti-aces of the primordial wall). In 

 other parts of the section the tube-cavities and walls are largely 

 obhterated by stellate crystallization. 



Fig. 1 c. Vertical section of the same specimen, enlarged twelve times. 

 The dark vertical fines (v) represent the axial lines of the tube- 

 cavities ; but in places portions of the visceral chambers are not 

 infiltrated with the darker destructive material, and stiU exhibit 

 tabulae {t). t 



Fig. 2. Tangential section of R. stromatoporoides, Roem., in the typical 

 " stellimicans " state, enlarged twelve times. The visceral cham- 

 bers and walls are completely obliterated by stellate crystalliza- 

 tion. Middle Devonian, Gerolstein. 



Fig. 2 a. Part of another tangential section of the same specimen, enlarged 

 twenty times. In this part of the section the tubes are much 

 below the average size. On the right hand side of the figure 

 the stellate ciwstallization is completely developed ; but towards 

 the left the visceral chambers are not infiltrated with the darker 

 material. The walls are obliterated throughout. 



Fig. M. Part of a tangential section oiR. stromatoporoides, Roem., enlarged 

 twenty times. The walls of the corallites are still quite recog- 

 nizable, but the visceral chambers are occupied by stellate ciys- 

 tallization, the fibres of which sti'ike through the walls and 

 give to the latter the aspect of being crossed by transverse dark 

 bars. Middle Devonian, Gerolstein. 



Fig. 4. Vertical section of a double colony of R. stroinatoporoides, Roem., 

 enlarged twelve times. The lower colony (A) is in the normal 

 state; the upper colony (B) is in the ^^ steUiitiicans" state; and 

 the two are separated by a well-marked interval. In the upper 

 colony the axes of the visceral cavities" are marked by vertical 

 dark lines (v), and the fainter lines (w) between each pair of 



