Prof. W. King on Spirifer cuspidatus. 11 
settled, there can be no doubt that the phenomenon sought to 
be explained is the result of metamorphism; and I hold this 
to be completely proved by the fact that in metamorphosed 
examples of the tests of other Palliobranchs the perforations 
disappear just as they do in Spirifer cuspidatus. Of va- 
rious shells which I have examined, such as Dielasma (Te- 
rebratula) hastata, Pygope diphya, &c., may confine myself to 
Spiriferina laminosa*, M‘Coy, which hasaftorded methe clearest 
evidence in favour of the above conclusion. The latter species 
occurs in various conditions of fossilization: some of my spe- 
cimens have the test well preserved, others have it completely 
destroyed, and many have it in an intermediate condition. 
The best-preserved specimens (for which I am indebted to 
Mr. G. Tate, F.G.S., of Alnwick) that have passed under my 
examination are from Redesdale, in Northumberland. The 
fibres are well displayed, twisting about more or less, and 
separating or pushed aside by the intrusion of the perforations. 
In general the perforations are well defined, so that their dia- 
meter, which is -1; inch, can be tolerably well determined. 
They occur pretty regularly at about =, inch from one an- 
other; but occasionally a smaller perforation makes its ap- 
pearance in the intermediate spaces: their contents consist of 
translucent granules, a dark-coloured matter, or a dusky-white 
substance. Under a magnifying-power of 120 diameters, the 
dark-coloured matter resolves itself into a congeries of crys- 
tals of pyrites. Here and there a section appears without any 
perforations; or some present themselves more or less obscurely, 
either as ill-defined aggregations of granules or indefinite 
dusky spots; the former are occasionally somewhat enlarged. 
From the less clear appearance of the fibres in such places, 
the absence or the obscurity of the perforations is evidently 
due to a change in the shell-tissue. It is noteworthy that the 
fibres, where mere traces of the perforations occur, occasionally 
display only faint or uncertain indications of their deflection ; 
rather they appear to continue straight on in their course. 
Specimens which I have examined from other localities differ 
remarkably from those collected at Redesdale. Mr. W. H. 
Baily, Paleontologist to the Irish Geological Survey, has 
favoured me with some from Hook Point and Tipperary ; but 
they are all so completely silicified that nothing more than the 
fibrous structure is retained. I have also succeeded in obtain- 
* Mr. Davidson and others have placed this species in Spirifer; but it 
undoubtedly belongs to Spiriferina. All the localities from which I have 
examined specimens have yielded me dorsal valves of it with the medio- 
longitudinal plate characteristic of the latter genus. 
