Prof. T. Rupert Jones — South Wales Entomoatraca. 215 



Williamson, sp. ; and amongst these shells are a few others, flifioriiij; 

 very slif^htly in shape, hut characterized by their minutely reticu- 

 late surface, therein resembling Estherta. There are also a ievv speci- 

 mens of Estherta ienella, and numerous small Oytheroid forms, 

 which cannot belong to either Cythere or the allied genera, as 

 far as the cara])aces show. In some pieces of the bituminous 

 shale another Entoniostracan Bivalve, namely, Leaia, occurs in 

 abundance on some slabs, but without associates. This genus is 

 now for the first time found so far south in Britain ; the hitherto 

 known specimens have come from different parts of North America 

 (Pcuns3dvania, Illinois, and Nova Scotia), from Scotland, Lan- 

 cashire, and Germany. A layer of what at first sight appear to 

 be small Seeds or Spore-cases coats one face of a slab rich with 

 Anthracomya and Estheria, but these little bodies are possibly small 

 Daphnia-like Entomostraca, as suggested by Mr. Carruthcrs, F.G.S. 

 A single larger Spore-case (?) occurs on another piece, and a Lcpido- 

 dendroid leaf on another. In some of these shales there occur black 

 shining circular spots, with irregularly concentric wrinkles, that at 

 first sight look like compressed fruits ; but Mr. Carmthers has 

 explained (Brit. Assoc. Meeting, 1869) their nature and origin, as 

 spots where gases, disengaged from decomposing organic matter, 

 formed bubbles, imprisoned in the mud ; and, whilst gradually 

 diminishing, their successive walls were again and again squeezed 

 and slickensided by the double action of pressure and expansion. 

 The less bituminous shale contains fragments of Neuropteris and 

 Cyclopteris (?). Fish (?) bones also occur on some of the slabs. 



These shales, associated with " Black Band Ironstone " of the 

 South-Welsh Coal-field, are regarded by Mr. Adams as the equivalent 

 of the bed referred to as "Eider [Coal], 1 foot," in the Section of 

 sti'ata of the "Pennant" series, at page 172 of the Mem. Geol. 

 Survey, Iron-ores, Part iii., 1861. Mr. Adams informs mo that 

 " about one and a half mile south-west of Bedwelly Church, and 

 one and a quarter mile north-east of Gelligaer Church (on 

 Sheet 36 of the Ordnance Survey Map), in Glamorganshire, on the 

 west side of the Eiver Eumney, a coal-level was opened on the crop 

 of the Mynyddysllwyn Coal, on Cilfach-bargoed-fawr Farm. After 

 driving westward in the coal, they struck a down-throw west fault 

 (from 25 to 30 yards) ; and in place of the coal, or rather on the 

 same level, came in the Black Band beds, and in these the fossil 

 shells are found. (See Section.) The Black Band is apparently of 

 limited area. This new bed of fossil shells is about 800 ft. higher in 

 the South-Welsh Coal-measures than any hitherto met with. At 

 Llancariach Colliery, the property of George Worthington, Esq., 

 1\ miles nearly due west from Gelligaer Church, this Black Band 

 again occurs, with the same fossil shells, some acres in extent, but of 

 less thickness than at the works above mentioned ; and here also it 

 is between two faults." 



A shale full of Anthracomyce of the same species as that above 

 noticed has also been found by Mr. Adams at Aberbeeg, in the Ebbw 

 Yalley, overlying a coal called the Troed-rhiw-Clawdd Coal, which 



