CARBONIFEROUS AND PERMIAN MONOGRAPHS. 267 



present case more especially, for Permian shells as a rule are of smaller size than Car- 

 boniferous ones. 



Carboniferous Names. Permian Names. 



Spirifera Urii, Fleming, sp. 1828. Lav., Spirifera Clannyana, King, sp. 1848. 

 pi. liv, fig. 14. Lav., pi. liv, fig. 15. 



Prof. King denies the identity of these two shells, although allowing them to be closely 

 related ; but after having compared many examples of the Carboniferous and Permian 

 species? neither Mr. Kirkby nor myself could perceive any valid specific difference 

 between them. 1 



Spiriferina octoplicata, Sow., sp. 1827. Spiriferina cristata, Schloth., sp. 1816. 

 Lav., pi. liv, figs. 10 and 12. Lav., pi. liv, figs. 11 and 13. 



It appears to me, as well as to my friend Mr. Kirkby, that there cannot exist a doubt 

 as to these shells belonging to a single species, for which Schlotheim's name should be 

 preferred. None of the Permian examples that have come under our observation have 

 attained the dimensions of certain full-grown Carboniferous specimens, but the general 

 character in both is specifically the same. 



Camarophoria crtjmena, Martin, sp. 1809. Camarophoria Schlotheimi, v. Buck, sp. 

 Lav., pi. liv, figs. 16, 17, 18. 1834. Lav., pi. liv, fig. 19. 



I feel satisfied that my identification of the Permian C. Schlotheimi with Martin's 

 Anomites crumena is correct. Prof. King has admitted that the last-named shell is a 

 Camarophoria, but believes it specifically different to C. Schlotheimi. I have, however, 

 found Permian specimens agreeing very closely with Martin's imperfect figure, and am 

 not acquainted with any other Carboniferous Camarophoria to which the Permian shell 

 could be assimilated than the one we recognise as crumena. In C. Schlotheimi the mesial 

 fold varies in width and elevation according to the number of ribs which ornament its 

 surface, these varying usually from two to seven, and from one to six in the sinus, while in 

 the Carboniferous shell the same differences are observable, as may be seen in figs. 3 — 9 

 of PI. XXV. It is, therefore, evident that one of the two above-mentioned names will 

 have to be erased, and as Martin's species possesses claims to priority, its name will have 

 to be retained for the Permian as well as the Carboniferous specimens. 



1 The term recurrent has been applied by palaeontologists to such species as occur in more than one 

 formation or system of strata. In this sense I use it here. For instance, as I consider Spirifera unguiculus, 

 Sow. of the Devonian, Sp. Urii of the Carboniferous, and Sp. Clannyana, king of the Permian system, to 

 be same species, it is said to be recurrent, because it reappears or recurs in two distinct groups of strata 

 after its first appearance in the Devonian system. The term also necessarily implies that the species 

 existed during the whole of the period that is included between its first and last appearance. 



34 



