197 
towards its frontal extremity there are two rudimentary folds causing an 
equally rudimentary fold at the frontal edge of the ventral furrow. Both 
valves possess from eight to twelve angular folds, by which the whole surface, 
including the ventral furrow and the dorsal ridge, is covered with thin, 
concentric, imbricated plates. The test is perforated, and consequently 
covered with an immense number of small asperities. In the centre of the 
ventral valve is a septum generally more developed in proportion than in most 
of the other species of Spirifer, among which it is often only rudimentary. 
Dimensions. — These are very irregular. The length rarely exceeds 
fifteen millimetres, and the breadth twenty-five millimetres. 
Relations and Differenees. — It is now generally agreed that the 
Carboniferous species figured by Sowerhy under the name S. octoplicatus, is 
identical with the Permian species first described by von Schlotheim under 
the name Terehratulites cristata. This was my opinion in 1843, and it was a 
mistake to abandon it later on as I did. This Spirifer is easily distinguished 
from the following species by being more transverse, and by having more 
folds. 
Horizon and Localities. — As this species recurs after, and has 
survived, the deposition of the Carboniferous rocks, it is easy to suppose that 
it belongs essentially to the upper beds of that System. I have found it 
frequently in the Vise Limestone ; and it occurs in Derbyshire, Yorkshire, 
Scotland, and Ireland. Mr. W. B. Clarke found a single specimen of it in a 
quartzose sandstone at Colocolo. 
Spiriferina insculpta, J. Phillips. 
Spirifera insculpta, ,J. Phillips, 1836, G-eol. Yorkshire, II, p. 216, pi. 9, fig. 2, 3. 
Spwifer Ctdspns, L.-GT. de Koninck, 1843, Descr. Anim. Foss. Terr. Garb. Belg., 
p. 257, pi. 15, fig. 7, 8 (non LinncTens). 
Spirifera quinqueloha, F. McCoy, 1844, Synop. Garb. Foss. Ireland, p. 134, pi. 22, fig. 7. 
,, ,, Von Semenow, 1854, Ueber die Foss. Scbles. Koblenkalkes, p. 14. 
Spiriferina ? insculpta, T. Davidson, 1857, Mon. Brit. Garb. Bracb., p. 42, pi. 7, fig. 48-55. 
Spirifer insculptus, E. d’Eicbwald, 1860, Lethsea Eossica, I, p. 709. 
Spiriferina insculpta, T. Davidson, 1860, Mon. Garb. Bracb. Scotland, p. 24, pi. l,fig. 35. 
This is a small, sub-rhomboidal, slightly transverse shell, with a straight 
hinge line occupying the greatest breadth of the valve. The hinge area is 
