120 . CARBONIFEROUS LAMELLIBRANCHIATA. 



8. Sowerbyi, and its name must be placed as a synonym. I am not persuaded of 

 the specific value of 8. Witryi, de Koninck. 



8. Sowerbyi seems to have a very wide horizontal and vertical distribution. 



A specimen in the Leckenby Collection, Woodwardian Museum, No. 123 (PI. 

 XVIII, fig. 21), locality unfortunately unknown, shows a curious system of colour- 

 bands arranged in slightly undulating, concentric lines, which start from the anterior 

 margin, pass obliquely upwards to the centre of the valve, and then descend again to 

 the posterior margin, the angle formed by the two limbs being very wide. De Koninck 

 has described a somewhat similar form of marking, forming a species, Entolium 

 coloratum, on this single character. The arrangement of the colour-bands differs in 

 his specimen, being less regular. I doubt if the shape of his figure is correct ; 

 probably it is incomplete, there being no lateral flanges, and I think it probable 

 that this character is a generic one. 



Stnotclonema carboniferum, sp. nov. Plate XIX, figs. 3 — 6. 



Specific Characters. Shell small, obovate, expanded, very slightly convex; 

 more so near the umbo. Margins of valve small, the anterior the larger. Hinge- 

 line narrow. Ears triangular and raised so that their upper margins meet at the 

 umbo at an obtuse angle, the anterior a little larger and deeper than the left. 

 Umbones small, pointed, swollen, not elevated. Shell very thin. 



Interior. — As in S. Sowerbyi 



Exterior. — The surface is ornamented with very fine, close, concentric ribs, 

 only visible under the microscope. Ears smooth. 



Dimensions. — PI. XIX, fig. 5, a right valve, measures — 



Antero-posteriorly . . . .11 mm. 



Uorso-ventrally . . . .15 mm. 



Locality. — England : the Marine Band above the Gin Mine Coal, Nettlebank 

 Sinking, Smallthorne, North Staffordshire Coalfield. 



Observations.- — This little shell occurs plentifully in a bed of grey shale with 

 calcareous bullions at the horizon and locality mentioned above. The Gin Mine 

 Coal is high up in the Coal Measures, and occurs about 430 yards below the Bassy 

 Mine Ironstone, which is taken as the base of the Upper Coal Measures. This bed 

 was recognised by Mr. Ward so long ago as 1865, while a sinking was going on 

 at the Speedwell Colliery, Longton, and it was not until March, 1903, when Mr. 

 Stobbs, mining lecturer under the Staffordshire County Council, noticed marine 

 shells in the spoil-heap from a sinking at Nettlebank, that this marine bed was 

 noticed again. The bed is of great importance, evidently, as a guide to the coal 

 immediately below it, and the value of fossil evidence in mining is demonstrated. 



