BRITISH CARBONIFEROUS BRACHIOPODA. 279 



gical Survey, to Prof. L. de Koninck, he at once appeared disposed to refer it to a large 

 variety of Chonetes concentrica ; but as none of the Belgian specimens from the Lower 

 Carboniferous Limestone of Vise have attained more than about one third of the dimensions 

 of our Scottish examples, and as the concentric ridges are so much more numerous in 

 these last, I have adopted our friend's identification with some reserve, and especially so 

 as our Scottish material is very imperfect, and hardly sufficient to justify a positive 

 conclusion. Sp. ovalis, Strep, crenistria, Prod, scabriculus, &c, occur in the same locality. 

 Prof, de Koninck describes his C. concentrica as small, transversely semicircular; 

 ventral valve very slightly convex, dorsal one very feebly concave, surface of each valve 

 ornamented with from twelve to fifteen concentric ridges. 



In the explanation of PI. XLV, with figs. 1 — 6, write "Productus Llangollensis' 

 instead of " Chonetes comoides." 



Before concluding this Appendix I must briefly allude to several casts and impressions 

 of a Chonetes recently discovered by Mr. J. Kirkby, in a Lower Permian Limestone, at 

 Hartley quarry, Sunderland, in Durham, and which will thus add another species to our 

 list of British Permian Brachiopoda. 



These casts exactly agree in shape and dimensions with Phillips's Chonetes Hardrensis, 

 and to which species I should have at once referred them had I been able to satisfy 

 myself that the external markings, striation, &c, were those of the Carboniferous shell. 



These casts are smooth, and show no evidence of striation, and some examples, 

 without considering dimensions, bear some resemblance to Schauroth's Permian Chonetes 

 Davidsoni. 1 



All I can, therefore, at present say with regard to these interesting specimens is that 

 the shell is marginally semicircular, wider than long, plano-convex ; hinge-line straight, and 

 either a little shorter or as long as the width of the shell ; that each valve is provided with 

 a sub-parallel area, but which is widest in the ventral one, and divided in the middle by 

 a small fissure, partly arched over by a pseudo-deltidium. The ventral valve is mode- 



1 " Ein neuer Beitrag zur Palaontologie des deutschen ZechsteiDgebirges " (' Abdruck. a. d. Zeitscbr. d. 

 deutschen Geologischen Gesellschaft,' Jabrg, 1856, pi. xi, fig. 1). 



Baron Scbauroth's C. Davidsoni appears to be a small shell, not exceeding tbree lines in length by about 

 four in breadth, is semicircular, but comparatively and proportionately longer than wide than is C. Hardrensis ; 

 concavo-convex, with six slanting spines on the cardinal edge. The surface is marked with numerous 

 concentric lines of growth, which are crossed by some radiating striae. It is now an undoubted fact that 

 Chonetes has continued to exist since the Lower Silurian epoch up to the Permian one inclusive. 



35* 



