398 Dr. H. A. Nicholson and Mr. A. H. Foord on a 



species under the name of Pachytheca stellimicans (Sitzungs- 

 berichte der niederrhein. Gesellsch. in Bonn, 1885). Even on 

 the supposition that these appearances are organic, we should 

 be unable to accept this name, either as regards the species or 

 the genus, since it can be shown conclusively that the species 

 is the Chcetetes stromatoporoides of Roemer *, while the name 

 of Pachytheca has been preoccupied by Sir Joseph Hooker 

 for certain problematical bodies from the Ludlow rocks of 

 Britain f. 



EXPLANATION OF THE PLATES. 

 Plate XV. 



Fig. 1. Tangential section of Rhaphidopora crinalis, Schlliter, enlarged 

 twelve times. The section is taken fi-om the type-specimen of 

 Chcetetes Lonsdalei, Eth., Jim., & Foord, and is from the Devo- 

 nian of Teignmouth. 



Fig. 1 a. Vertical section of the same, similarly enlarged. 



Fig. 2. Tangential section of a specimen of Rhaphidopora crinalis, 

 Schlut., from the Middle l)evouian of Soteuich, in the Eifel, 

 enlarged twelve times. The tubes are somewhat larger than in 

 the typical examples of R. crinalis ; but this would not appear 

 to be a difference of specific value. 



Fig. 2 a. Vertical section of the same, similarly enlarged. 



Fig. 3. Tangential section of a specimen of Rhaphidopora crinalis, 

 Schliit., from Gerolstein, in the Eifel, enlarged twelve times. 

 In this specimen, as in the preceding, the tubes are somewhat 

 larger than in typical examples of the species. 



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



Fig. 4. Tangential section of Rhaphidopora erinalis, Schliit., var. acule- 

 ata, Nich. & Foord, enlarged twelve times. Middle Devonian, 

 Gerolstein. 



Fig. 4 a. Part of the same section, enlarged twenty-four times. The 

 dark transverse bars visible here and there, crossing the walls of 

 the tubes in tangential sections, are not due to the presence of 

 mural pores, but seem to be the result of mineralization. 



Fig. 4 h. "S'ertical section of the same, enlarged twenty-four times, s, the 

 cut extremity of one of the septal spines. 



Fig. 5. Tangential section of a specimen of R. stromaioporoides, Roem., 

 in which the visceral chambers are open and the walls distinct, 

 enlarged twelve times. Middle Devonian, Gerolstein. 



Fig. 5 a. Part of the same section, enlarged twenty-four times, showing 

 the septal spines. 



Fig. 5 h. Vertical section of the same specimen, enlarged twelve times. 

 In the upper portion of the section destructive infiltration has 

 set in, and the visceral chambers are partially obliterated. 



* We have examined an example of R. stromatoporoides kindly sent us 

 by Professor Roemer himself. 



t Quart. Journ. Geol. Soc. vol. ix. p. 12 (1853) : ibid. vol. xvii. p. 162 

 (1861). 



