466 THE GEOLOGTST. 
■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, Spirifenm, Cyrtina, 
Athjris, and Retzia, at present known, may, perhaps, be provisionally 
arranged in the following order : — ■' 
1. Spieifeea striata, Martin, sp., Pet. Derb. tab xxiii. 1809 : Dav. Brit. Foss. 
Brack., part V. pi. ii. figs. 12-21 ; pi. iii, fig. 2-6=7'. 
spirifera, Lamarck. = altenuata, J. de C. Sow. = princeps 
and clatharata, M'Coy. This species must be looked 
upon as the type of the genus. 
2. ,, MosQrENSis, Fischer de Waldheim, Prog, sur les Choristite, p. 8, 
N. 1, 1825, Dav. pi. iv. fig. 13, 14, and pi. xiii, fig. 
16 = Scwcrbf/i and Eleinii, Fischer = incisa Goldfuss = 
Chorislites v. Buch. z=: prisms Eichwald. This form is 
much rarer than the preceding one, and occurs principally 
in Ireland. 
3. „ ETJJiEEOSA, Phillips. Geol. of York, vol. II, pi. xi, fig. 8, 1836 : and 
Dav. pi. iv, figs. 15, 16. 
4. „ DUPLicicosTATA, FMUips, Geol. of York, pi. x, fig. 1, 1836 : and 
D-av., pi. iii, fig. 7 — 10 : pi. iv, fig, 8, 5 — 11 = fasciffer, 
Keyserling = fascicidata, M'Coy. 
N.B. — AH these forms are closely related, 
?5. „ CEASSA, de Koninck. An. Foss. de la Belgique, pl.xv., 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 iS^. 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 
Brachiopoda, published by the Palseontographical Society. 
