316 Pohvozoic Corah I'n the Brillsh Museum. 



with accuracy as to the number of these spines on account of 

 their imperfect state of preservation. The tabulge are very 

 numerous, and often anastomose. The mural pores are large 

 and in two alternating rows. 



Obs. In his remarks upon the genus Thecia Dr. Nicholson 

 has drawn attention to the great discrepancy which exists 

 between Dr. Rominger's description of Thecia and the charac- 

 ters of the type species T. Srvindennana. AYe are prepared 

 to add our testimony in this respect to that of Dr. Nicholson, 

 and to go much further, and to show that two out of the 

 three species described by Dr. Rominger * under the generic 

 name of Thecia belong to the genus Favosifes ; these are 

 Thecia {Favosites) major and Thecia {Favosifes) ramosa. 

 Upon the specific identity of the last-named species we are 

 unable to offer an opinion, owing to the very unfavourable 

 condition of the specimen. It may be observed, however, in 

 passing that Dr. Rominger remarks f that it is sometimes 

 difficult to distinguish specimens of this form from " similarly 

 altered stems of Favosites racliciformis^ with which they are 

 found associated." The remaining species, viz. Thecia minor ^ 

 is without doubt a Thecia. Its external characters, where 

 these are well preserved, are so like those of T. Swindemiana 

 (with which its author has indeed compared it), that we should 

 hesitate to separate it from that species. Its internal struc- 

 I'Are has been much obscured by becoming beekitized. 



The mingling of two distinct types [Thecia and Favosites) 

 under one generic description accounts for the divergence 

 between the characters of Thecia as elucidated in the first 

 instance by Milne-Edwards and Jules Haime |, and more 

 recently by Nicholson §, and Dr. Rominger's definition of the 

 genus. It should be noted that Dr. Rominger institutes a 

 comparison between his Thecia major and Favosites Forhesi 

 (var. diseoidea), as figured and described by Dr. Ferdinand 

 Romer in his ' Silurian Fauna of Western Tennessee/ and 

 further, in his description of T. major, remarks upon the 

 *' perfect correspondence of the structure of Thecia with Favo- 

 sites " as exemplified in one of the specimens he figures ||. 

 We can trace no specific resemblance between the present 

 species and Favosites Forbesi, var. discoidea \ but it is inter- 

 esting to observe the tendency in the mind of the author of 



• Loc. fit. p. 67. 



t Loc. cit. p. 69. 



\ 'Comptes Rendus,' t. xxix. p. 263 (1849). 



§ Pal. Tab. Corals, p. 236 (1879). 



II Loc, cit. pi, xxy. tig. 2. 



