466 THE GEOLOGIST. 



well as of species belonging to other genera.^' And even out of the forty 

 here retained, a few will require some further investigation in order to 

 ascertain whether or not they may be varieties of those already 

 described. It is, therefore, probable that the number above given may 

 still be somewhat diminished by reducing a few of the so-named species 

 to the rank of varieties. Some naturalists and geologists have cast a 

 not always unmerited reproach upon the species-makers, and I would 

 be the last person to deny the great injury that has accrued to science 

 by this useless burdening of the nomenclature ; but I may be permitted 

 also to observe, that the difficulty in discriminating the characters, values, 

 and limits of species is far greater than is, perhaps, conceived by persons 

 who have not studied the subject, or by others who, from local 

 and fortunate circumstances, may have been able to discover certain 

 passages of form connecting one or more of the so-termed separate 

 species. I applaud their efforts, and am always delighted to be put 

 right when I may have erred; for my only object is the advancement 

 of the science to which I have already devoted upwards of twenty- 

 five years of my existence. 



The species of British Carboniferous Spirifera, Spiriferinai Cyrtina, 

 Atliyris, and Ret%ia^ at present known, may, perhaps, be provisionally 

 arranged in the following order : — 



1. Spieifera steiata, Martin, sp,, Pet. Derb. tab xxiii. 1809 : Dav. Brit. Foss. 

 Bracla., part Y. pL ii. figs. 12-21 ; pi. iii, fig. 2-6=1: 

 sj)irifera^ Lamarck. =-attenuata, J. de C. Sow. =.pnnceps 

 and datharata, M'Coy. This species must be looked 

 upon as the type of the genus. 



2. „ MosQUENsis, Fischer de Waldheim, Prog, sur les Choristite, p. 8, 

 N. 1, 1825, Dav. pi. iv.,- fig. 13, 14, and pL xiii, fig. 

 16 = Sowerhyi and Kleinii^ Fischer = incisa Goldfuss = 

 Choristites v. Buch. z=z prisms Eichwald, This form is 

 much rarer than the preceding one, and occurs principally 

 in Ii-eland. 



3. „ HrMEEOSA, Phillips. Geol. of York, vol. II, pi. xi, fig. 8, 1836 : and 

 Dav, pi, iv, figs. 15, 16. 



4. „ DUPLicicosTATA, Phillips, Geol. of York, pi. x, fig. 1, 1836 : and 

 Dav., pi. iii, fig. 7 — 10 : pi. iv, fig. 8, 5 — 11 — fasciger, 

 Keyserling = fasciculata, M'Coy. 



N.B. — All these forms are closely related. 



?5. ,, CRAssA, de Koninck. An. Foss. de la Belgique, pl.sv., bis fig. 5, 

 1843 : and Dav. pi. vi., figs. 20 - 22 : pi. vii., fig. 1 - 3 

 = planicosta, M'Coy. By some this shell is placed among 

 the synonyms of Sp. duplicostata, by others among those 

 of Sp. bisulcata, and it certainly sometimes possesses 



* A list of these will be found in my Monograph of British Carboniferous 

 Braohiopoda, published by the Palceontographical Society. 



