336 CARBONIFEROUS LAMELLIBRANCHIATA. 



from the umbo to the postero-inferior angle is an obscure ridge, above which the 

 shell is compressed and slightly expanded. 



Interior. — Not exposed. 



Exterior. — The surface is almost smooth, but the microscope shows very fine, 

 close, and regular concentric lines, more pronounced on the dorsal slope. Shell thin. 



Dimensions. — Fig. 7, PI. XXXVII, measures — 



Antero-posteriorly . . . .29 mm. 



Dorso-ventrally . . . .23 mm. 



Elevation of valve . . . .8 mm. 



Localities. — Scotland: the Upper Limestone series of Kirktonholm, East 

 Kilbride, in the Cement stone. 



Observations. — De Koninck founded the species S. fragilis on a single some- 

 what imperfect valve from the Calcschist of Tournay, and his description is 

 therefore necessarily meagre. The specimens which I have referred to this 

 species are from the cabinet of Mr. J. Neilson, and seem to agree perfectly with, 

 de Koninck's figures. One example, PI. XXXVII, fig. 7, is fairly perfect; and 

 another, PI. XXXVII, fig. 6, has the greater part of both valves preserved. I have 

 not been able to see any details of the hinge or the interior in the specimens from 

 East Kilbride, the locality where Mr. Neilson obtained his specimens, but Mr. Smith 

 of Kilwinning has a fragment of a valve from Glencart, Dairy, which shows the 

 characteristic single hinge-tooth of Scaldia ; but there is not enough left of the 

 shell to speak accurately about its specific affinities, and the surface markings are 

 too pronounced to refer it to the species under discussion. 



Scaldia fragilis is distinguished from other species of the genus by the presence 

 of the slight oblique ridge separating the dorsal slope from the rest of the valve. 



Scaldta Benedeniana, de Rychholt, 1852. Plate XXXVII, figs. 1—3. 



Scaldia Benedeniana, de Eyckholt, 1853. Melanges pak'ontol., pt. 2, \>. 71, 



pi. xiv, figs. 30, 31. 

 Caediomorpda sector, de RycMolt, 1853. Ibid., p. 97, pi. xiii, fig. 9. 

 Scaldia Benediana, liigsliy, 1S77. Thesaurus Devonico-Carbouiferus, p. 313. 

 — de Koninck, 1885. Aim. Mus. Roy. d'Hist. Nat. Belgique, 



torn, si, p. 55, pi. xiv, figs. IS — 20, 44. 



Specific Characters. — Shell below medium size, suborbicular, very slightly 

 oblique, gibbose, somewhat inequilateral. The border is regularly rounded, and 

 passes in a continuous curve from the antero-superior border to the hinge-line 

 just posterior to the umbones. The hinge-line is regularly arched. The umbones 

 are tumid, incurved, and twisted forwards, contiguous and raised above the 



