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SUPPLEMENT TO THE BRITISH 
I have also verified, that well-preserved shells of Sp\ mspidata show perforations more 
or less distinctly, but are associated with others in which they have become obliterated, 
or appear in a patchy condition, in the midst of wide imperforate spaces. 
Interior of the large or ventral valve. — In 1863 Prof. Winchell describe^ this valve as 
" a shell with an elongated hinge-line, a mesial sinus, a broad area, and a narrow, 
triangular fissure closed towards the apex by an external convex pseudo-deltidium, 
beneath which, and diverging from it, is another transverse plate connecting the vertical 
dental laminae arched above, and beneath giving off a couple of median parallel lamellae, 
which are incurved so as to nearly join their inferior edges, thus forming a slit-bearing 
tube (Sup., PI. XXXIII, fig. 3 «), which projects beyond the limits of the plate from 
which it originates in the interior of the shell." 
As I stated in 1867, Prof. Winchell was not aware that the characters assigned by 
him to his genus had been already illustrated and defined by Prof. L. de Koninck in the 
' Transactions of the Royal Society of Liege ' for 1859. These characters were found to 
exist in a Belgian example of Syringothyris {Spirifer) distans, where the transverse plate 
is not quite connected along the centre, but bends underneath on both sides, and forms 
under it a disunited, tubular canal ^ (Sup., PI. XXXIII, figs. 4, 5). There does 
not appear to exist in the interior of the ventral valve any median elevated septum, as in 
Spiriferina, nor are the dental plates united in the last-named sub-genus by a transverse 
plate. It differs, also, in the arrangement of its dental plates, from what we find to be 
the case in Cyrtina, of which I have given a detailed description at p. 68 of my 
Monograph. I have not, I am sorry to say, been able to procure any interiors of British 
examples of Syr. ciispidata, nor any internal casts exhibiting the muscular impressions ; 
but in a beautifully preserved internal cast of a specimen evidently belonging to the 
species, from the Carboniferous formation of the State of Ohio, and generously presented 
to me by Prof. L. de Koninck, I was able to study the shape and characters of these 
impressions. This cast was subsequently described and illustrated from figures of my 
own by Prof. King in his Monograph of Sp. ciisjndata in ' Annals and Mag. of Nat. 
Hist.' for July, 1868, to which the reader is referred. I regret, likewise, that it has 
not been possible to procure any specimen in which the spiral processes were in place. 
After many attempts the Rev. Norman Glass developed them partially in one specimen 
(Sup., PI. XXXII, fig. 16), but although one of the spirals was complete, it had been 
broken from its attachment to the base of the hinge-plate previous to the shell being 
filled by the limestone or spar that forms its matrix ; of the other spiral coil only a small 
part is seen, and is apparently in its natural position, but the attachment and direction 
remain obscure. 
1 See my paper in the ' Geol. Mag.,' vol. .\iv, pi. xiv, figs. 6, 8, 1867. 
