252 ON THE PERMIAN CHITONIDJi:. 



similar in form, as well as some of the intermediate plates of 

 other recent Chitons. The only fossil species whose equivalent 

 plates appear to possess any close affinity to the present are those 

 of the Upper Silurian C. Wriglitianus of De Koninck,* and those 

 of C. Sluseanus, De Ryckholt.l It is rare, and has only been 

 found in the shell-limestone of Tunstall. 



[Since this paper was read, I have discovered at Tunstall Hill 

 a peculiar plate of a Chiton, which differs in form from any that 

 have hitherto come under my observation. It is apparently an 

 anterior plate; and it is just possible that it may be the first of 

 the series of C.' cordatus. It is represented by figs. 54, 55, in 

 the plate accompanying this paper. — J. W. K., Aug. 24.] 



Subgenus CHITONELLUS, Lamarck. 



Only one representative of this subgenus appears to have been 

 found in a fossil state previous to the discovery of the following 

 species. In 1847 Baron De Ryckholt described a very interest- 

 ing fossil from the Carboniferous system of Belgium, which he 

 named Chitonellus Barrandeanus .% The general character of 

 this plate seems to indicate an affinity to the ChitonelU, to which 

 it has probably been rightly referred, though at the same time 

 it would be well to know something of its process of insertion 

 before speaking positively on the subject. Another fossil from 

 the same system has also been placed in this group by Prof. De 

 Koninck, though evidently with some doubt. § De Ryckholt 

 seems to have proved, however, that this plate does not belong to 

 any member of the Chitomdce, but rather to one of the Crinoidea. \\ 

 Mr. J. W. Salter stated in 1847 that even De Koninck himself 

 had admitted that it belonged to the latter.^ More recently, 

 however, the learned professor again refers to it as Chitonellus {!) 

 cordifevj as though he had not altered his first opinion.** I am 



* Bull de I'Acad. R. Belg., 2me se'r., vol. iii., no. 11. 

 t Bull de I'Ac. R. Belg.,TOl. xii., no. 7, and vol. xxiv., p. 63. 



X Melanges PaMontologlques, par Le Baron P. de Ryckholt, Bull de I'^cad. Roy. Belg., 

 vol. xxlv., p. 63, pi. 2, figs. 37, 38. 



§ Bull, de I'Acad. Roj-. Belg., 2cne s^r., tome iii., no. 11. 



II BuU. de I'Acad. Roy. Belg., tome xii., no. 7. 



^ Quart. Jour. Geol. See, vol. iii., p. 49. 



** Bull, de I'Acad. Roy. Belg., 2me s^r., tome iii., no. 11. 



