150 



BRITISH SILURIAN BRACHIOPODA. 



Obs. Pentamerus linguifer is a much smaller and more stumpy-looking species 

 than P. galeatus, and is at once distinguished from it by having its mesial fold on the 

 dorsal valve, vi^hilst in Dalman's species it occurs on the ventral valve; and the same 

 apphes to the sinus. It is also smooth, and the fold is often somew^hat bent upwards 

 towards its exterior, as seen in fig. 1 5 ^ of our plate ; but this is not always the case, as 

 fig. II « exemplifies. Its interior is also well distinguished from that of P. galeatus by 

 the still smaller development of the conjoined dental lamellae, or the V-shaped chamber 

 in the ventral valve, as well as in the smallness of the vertical septum which supports it. 

 Dr. Lindstrom allows me to state that he considers his P. rotmdus to be a variety or a 

 small individual of the shell under description. Pentamerus {Spirifera ?) Bubo, Barrande, 

 though a somewhat larger shell, did appear to M. de Verneuil and myself, in 1847, 

 to be the same as our P. livguifer. When quite young, the fold and sinus are scarcely 

 apparent. 



Position and Locality. Pentamerus Unguifer appears not to be restricted to the 

 Woolhope and Wenlock hmestones and the Wenlock shales ; Mr. Salter says it is plenti- 

 ful in the Upper Llandovery conglomerates west of the Malvern Hills. Dr. Holl found 

 it in the Woolhope limestone, and in the shale iuimediately above it, at Malvern, at the 

 Pound and Crews Hill, both near Alfric, and four miles to the north of Malvern. I have 

 picked it up at the Rushall Canal near Walsall, at Dudley, and along the Benthall Edge 

 near Wenlock. The Geological Surveyors have obtained it from Presteign and May Hill, 

 as well as from other localities. Sir Roderick Murchison found it at Stumps Wood, 

 Valley of Woolhope, and Delves Green, in Wenlock shale. It has not, to my knowledge, 

 been found either in Scotland or Ireland, and Mr. Salter agrees with me. 



Abroad, it was discovered, for the first time, in the Upper Silurian beds of Gothland 

 by Lindstrom, and in Russia by Schmidt. 



Pentamerus rotundtjs, /. de C. Soto. (sp.). PI. XV, figs. 9 — 12. 



Atrypa rotunda, /. de C. Sow. Sil. Syst., pi. xiii, fig. 7, 1839. 



— — Phillips and Salter. Mem. Geol. Survey, vol. ii, part 1, p. 2/9, 1848. 



Hemithyris rotunda, M'Coy. Brit. Pal. Foss., p. 205, 18.52. 

 Rhynchonella — Morris. Cat. Brit. Foss., p. 147, 1854. 



— — Salter. Silur., 2nd edit., pi. xxii, fig. 18, 1859. 



Spec. Char. Orbicular, or a little wider than long; sides and front rounded; 

 ventral valve smooth and moderately convex to within two thirds of the length of the 

 valve, where a broad sinus commences and extends to the front ; two or three rounded 

 ribs occupy the sinus, while the lateral portions of the valve are either smooth, or orna- 

 mented by two or three ribs on each side, but these do not extend further than to a 

 very short distance from the margin ; beaks small, and but little produced beyond the 



