102 



BRITISH SILURIAN BRACHIOPODA. 



deltidium is likewise so difiFerent from that observable in Sjnrifera plicatella, that it is quite 

 sufficient to prevent the possibility of the last-named shell being considered as a variety, 

 due to a difference in shape, of Sjnrifera {Cyrtia) exporrecta : and the same would apply 

 to Sp. {C.) frapezoidalis, which is, as we have already shown, a synonym of Sp. exporreda. 

 It was long before I could expose portions of the spiral coils, and only after having 

 broken open a large number of specimens. These coils are disposed as in Spirifera ; 

 and the muscular arrangements are also the same. In the internal casts, as observed by 

 Prof. M'Coy, the slits left by the dental plates are very strongly marked in the ventral 

 valve, and our British examples agree entirely with those found in Gothland ; but 

 the deltidium is not correctly represented in either Hisinger's or Dalman's figures. 



Position and Locality. In England Sjnrifera exporreda ranges from the Lower 

 Llandovery to Ludlow Rocks (Salter), and is common in the Wenlock Limestone and 

 Ludlow Shale through Shropshire ; also of Dudley and Abberley ; the Wenlock Shale of 

 Rushall Canal, near Walsall ; of Craig-y-Garcyd, Usk ; of Nelson's Tower Wood, 

 Llandeilo. In fact, all through Carmarthenshire. It occurs too, but more rarely, in the 

 Upper Llandovery or May Hill Sandstone of Tortworth, at Damory Bridge ; in the Wen- 

 lock or Woolhope (Denbigh) grit of Plas MadoCj Llanrwst, and other places in Denbigh- 

 shire ; in the Woolhope Limestone, Storridge, and under Worcester Beacon, Malvern ; 

 and in the Lower Ludlow of Dog Hill, Ledbury. 



In Scotland it has been discovered by Messrs. Haswell and Brown, chiefly in the 

 condition of internal casts, in the Upper Silurian (Wenlock) shales of the Deerhope Burn, 

 near the North Esk Reservoir, Pentland Hills.^ 



be retained, it cannot, I think, be considered in any other light than that of a subgenus or section of tlie 

 great genus Spirifera. 



1 A specimen from this locality is figured in pi. iii of Mr. Haswell's little book on the ' Silurian 

 Formation in the Pentland Hills' (1865) ; but at that period, owing to the imperfect condition of the cast, 

 neither its species nor genus could be accurately determined. Since then, the discovery of more perfect 

 specimens has enabled me to refer without doubt these casts to Spirifera {Cyrtia) exporreda of 

 Wahlenberg. 



Since so many species of Brachiopoda have been discovered in the Upper Silurian rocks of the Pentland 

 Hills, it may be interesting to append a short note upon the subject, kindly forwarded to me by Mr. A. 

 Geikie, of the Geological Survey of Scotland. " Under the massive unconformable conglomerate of 

 the Pentland Hills, lies a series of highly inclined and even vertical strata, which for many years were 

 classed with the ' Grey wacke ' of the ' transition ' rocks of the south of Scotland. Two Orthoceratites 

 had been found in these strata previous to the year 1839, by the late Mr. Charles Maclaren, but the 

 specimens went amissing, and the species was not determined at the time of the publication of his ' Geology 

 of Fife and the Lothians.' One of the specimens eventually found its way into the Collection of Hugh 

 Miller, who showed it to me. It was lent by him some time before his death to Sir R. Murchison, with 

 the view of being named and described in the next edition of ' Siluria.' Before that edition appeared, 

 however, in 1858, the Geological Survey had began to map the area of the Lothians, and I had succeeded 

 in detecting in the so-called ' Greywacke ' of the Pentland Hills several other fossils. The Orthoceras 

 was named A. Maclareni ; and it most resembled a Wenlock species. The Silurian rocks of the 



