86 BRITISH SILURIAN BRACHIOPODA. 
I must again differ with my friend Mr. Salter when he proposes to include Cyrtia 
eaporrecta, Wahlemberg, and C. trapezoidalis, Dalman, amongst the varieties of Sp. 
plicatella. When describing these last-named shells my reasons for dissenting from this 
view will be given. 
Spirifer viator, Barrande (“ Silurische Brachiopoden aus Béhmen,” pl. xv, fig. 8, 1848; 
‘ Naturwissenschaftliche Abhandlungen,’ Bd. ui, p. 153)—Judging from the description, 
figure, and specimens, sent by M. Barrande to M. de Verneuil under that designation, it 
appears to us probable that Spirifer viator will require to be added to the synonyma of 
Spirifera plicatella, Linn. 
Position and Locality. Sp. plicatella occurs especially plentiful in the Wenlock 
shales in the neighbourhood of Dudley and Walsall, Staffordshire; in the Aymestry 
limestone of Aymestry; and the Wenlock limestone of May Hill, of Woolhope, Ledbury, 
Herefordshire, Benthall Edge, &c. Phillips and Salter mention the following localities 
(‘Mem. Geol. Survey,’ vol. ii, p. 293) :—Winning’s Farm (Malvern district) ; Hole Farm, 
Lower Ludlow (Abberley district) ; Checkley Common, Wenlock Shale (Woolhope district) ; 
Craig-y-Garcyd (Usk district); Nelson’s Tower Wood, Myddelton Series (Llandeilo 
avec ceux de l’Europe,’’ ‘ Bulletin de la Soc. Géol. de France,’ 2nd series, vol. iv, 1847) the Sp. cyrtena of 
Dalman as occurring at Lockport with Sp. Miagarensis, and occupying the same position in Europe. A 
careful comparison of our specimens of Sp. cyrtena from Gothland and specimens of Sp. radiatus of Sowerby 
from Dudley has convinced me that there is but a single species, and our specimens show, in a still greater 
degree, the variable character mentioned by Dalman. In the Swedish specimens the margin is usually 
plicated, the rounded plications sometimes extending half way to the beak, while in others they are only 
visible in the undulating outline, and sometimes are quite free from such characters. This plication of the 
margin appears not to be infrequent in the Dudley specimens, judging from those I have seen, and we may 
therefore regard the specimens from those localities as identical. In all the American specimens I have 
seen there is no evidence of this plication of the margin or surface, though in other respects they are almost 
identical with the specimens from Dudley, and it is not easy to point out any important characters by which 
they may be separated from the Swedish specimens. In well-preserved specimens from Gothland the 
strie are sharp, or round and prominent, and crossed by conspicuous, elevated, concentric striz, which 
towards the margin are undulated upon the elevations and depressions of the plications. All the New 
York specimens I have seen are destitute of the concentric striz, and the longitudinal striz are often 
flattened. This character, however, may arise from abrasion or partial exfoliation ; and in the shale, the 
presence of iron-pyrites, producing solution of the surface by sulphuric acid, is a probable cause of the 
absence of the more minute surface-markings. It is not a little interesting to the paleontologist and 
zoologist to consider the fact that, while we have no evidence of a plicated surface in this species from 
New York (and probably all American) strata, we yet have another species of similar form, and a similarly 
striated surface, which is distinctly plicated from beak to base, and never deviates even in the youngest 
specimens seen. This species (Sp. NMiagarensis) appears to be unknown in Europe, where the other 
species is common. We cannot avoid the thought that the manifestation of a peculiar feature in the 
Sp. radiatus of Europe was more strongly developed in a distinct but allied form in the western ocean, and 
which now appears as a characteristic species of the Niagara period. 
I may here observe, that in America occurs Spirifera plicatella, var. radiata, Sow.; and, according 
to Prof. Hall, not the true type of Linneus’s Sp. plicatella, which agrees with Sp. cyrtena of Gothland, 
and is also common in Britain. 
