APPENDIX 



TO THE 



CARBONIFEROUS AND PERMIAN MONOGRAPHS. 



Plate LIV. 



It is to be regretted that the series of Monographs on British Possil Brachiopoda, as 

 well as those relating to other classes, published by the Palaeontographical Society, had not 

 commenced with the species of the Silurian system, and progressed regularly upwards 

 to the Tertiary period. By such a mode of proceeding important advantages w r ould have 

 been obtained, from the possibility of tracing with more certainty and regularity the 

 recurrence of certain species, and thus have obviated the unfortunate necessity of occasional 

 alterations and repetitions to the parts already printed. The recurrence of certain species 

 in one or more systems is a subject of much importance, and is now an acknowledged fact, 

 but while there appears in some minds a manifest disinclination to admit such a thing 

 as possible, others have exaggerated the occurrence, and thus done more harm than 

 good. It would certainly be very agreeable and advantageous were there no recurrent 

 species, and that all the forms of each system or zone were characteristic to it ; but such 

 not being the case, we must unavoidably abandon preconceived ideas, and endeavour 

 to carefully trace the recurrence. I will not at present allude to those species which 

 are common to the Devonian and Carboniferous systems, as I have not yet critically 

 examined the Devonian forms, and shall therefore reserve what I might have to say upon 

 the subject until a future period, but it will be desirable to briefly refer once more to 

 those that appear to be common to the Carboniferous and Permian epochs. 



Several observers, among whom we may mention M. de Verneuil, Profs. King 

 and Morris, Messrs. Howse, Kirkby, and myself, have more than once alluded to the 

 strong resemblance — nay, identity — of certain Carboniferous and Permian species, 1 but 



1 My observations upon the recurrent forms in question will be found in various parts of my 

 Carboniferous Monograph, as well as in some numbers of 'The Geologist.' Mr. Kirkby's views are in- 

 corporated in his excellent paper, " On the recurrence of Lingula Credneri," &c, ' Journal of the Geo- 

 logical Society,' for March, 1858. 



