of Carboniferous Species. 20d 



them; and it' they are to be kept apart, it will certainly be upon 

 other than palseontological grounds. But figures form better 

 evidence than assertions either way ; and I would refer to Mr. 

 Davidson's representations of both Carboniferous and Permian 

 specimens, given in his Monograph of Carboniferous Brachio- 

 poda, pi. 54, and ask if it is possible to do otherwise than agree 

 with that gentleman in identifying these two forms as one 

 species. 



It must be acknowledged that it is not difficult to procure 

 specimens of Sp. Urii that show considerable differences when 

 compared with others of Clanmjana ; for this species is no ex^ 

 ception to others in possessing considerable individual differen- 

 tiation. And it would seem to be with some of the most aber- 

 rant of these that Prof. King has instituted his comparison. 

 The existence of such differences, however, can scarcely be of 

 much value, when they are wanting in other individuals allowed 

 to belong to the same species. At least, if the contrary is held, 

 in the face of a knowledge of their exceptional character, it 

 would certainly be more in harmony with the evidence to divide 

 the Carboniferous specimens into two species than to separate 

 them from those occurring in the Permian rocks. 



One difficulty which, until a recent period, had to be con- 

 tended with in comparing Carboniferous with Permian examples 

 of this shell was the imperfect condition in which most of the 

 latter occurred, nearly all being in the state of casts. Under 

 such circumstances it was not, perhaps, surprising that some 

 doubt should exist among palaeontologists on the propriety of 

 identifying the two forms ; but this difficulty is now removed 

 by the acquisition of testiferous Permian examples, one of which 

 Mr. Davidson has figured in the plate previously mentioned. 



It may also be observed that there is generally a difference in 

 the size of the Permian and Carboniferous examples — those of 

 Clannyana being almost invariably smaller than specimens of 

 Urii. And though few palaeontologists will be inclined to at- 

 tach much value to this as a specific character, it should yet be 

 pointed out that it is a peculiarity shared by many other Per- 

 mian shells when they are compared with those of Carboniferous 

 rocks. Permian Mollusca, as a rule, never attain the propor- 

 tions of Carboniferous, so far, at least, as those of British strata 

 are concerned. 



Camarophoria crumena and C. Schlotheimi. — Though Prof. 

 King disputes the identity of these shells, he admits the Per- 

 mian species to be recurrent from the Carboniferous Limestone. 

 The point of difference, therefore, between him and Mr. David- 

 son is merely whether the Carboniferous shell, which the latter 

 has compared with C. Schlotheimi, is correctly identified with 



Ann. $ Mag. N. Hist. Ser. 3. Vol.x. 15 



