326 



ME. HERBERT BOLTON ON 



[Aug. 1911, 



with Estheria cf. tenella (?), Bairdia cf. ampla (?), Esiheria sp 

 Anthracomya ivilliamsoni, and the following plant-remains : — 



Cordaites angulosostriatus 



Grand'Eury. 

 Cordaites-lea,\es. 

 Lepidophyllum sp. 

 Lepidodendron sp. (rimosum 

 Sternberg ?) 



Anmdaria cf. stellaia (Schloth.). 



Caidopteris sp. 



Pecopteris sp. 



Pecopteris cf. miltoni (Artis). 



Sphenopteris neuropteris Boulay. 



The agent of the Colliery Company, Mr. Hewitt, and the 

 manager, Mr. Eames, readily assisted in identifying the shale 

 lying upon the spoil-heap, which they considered came from the 

 roof of the High Vein. At my request, a quantity of fresh material 

 was cut out from the roof of this seam and brought to the surface, 

 when the horizon was at once put beyond doubt, the fresh 

 material containing hundreds of specimens of Leaia at all stages of 

 growth. Frequently this fossil occurred in clusters of a score or 

 more, the clusters being distributed sporadically oyer the slabs of 

 shale. The smallest forms are not more than 2 millimetres long, 

 and all sizes between this and 8 mm. in length are met with. 

 They are not always parallel to the bedding-plane of the shale, 

 but disposed at various angles. The stout straight ribs which 

 stand in high relief upon the surfaces of the valves vary in 

 number with the size of the fossil, small forms having as few as 

 twelve lateral ridges and adult forms nineteen. 



A cross-section of the valves shows that the dorsal face of each 

 rib is hollowed, the free edges of the ridges forming sharp knife- 

 like edges inclining towards the umbo. The lower or ventral 

 surface of each edge is convex. The radial ridges are sharply 

 angulated, prominent, and crossed by the concentric ribs, which in 

 well-preserved valves may impart to the line of the ridges a some- 

 what crenulated appearance. The hinge-line posterior to the umbo is 

 slightly excavated in some examples, enclosing a narrow elongated 

 area, which appears to have remained always open in the form of a 

 lunule. In front of the umbo, the hinge-line is carried a little 

 forward, and then merges into a well-rounded anterior border. 

 All the specimens found agree in general and detailed characters 

 with Leaia leidyi, var. salteriana, being shorter, deeper, and more 

 rounded than in the type-species of the genus or of the variety 

 williamsoni. 



The best-preserved forms show a well-marked convexity of the 

 valves and a fairly prominent incurved umbo. Paired valves are 

 rarely met with. Where they do occur, they show a markedly 

 truncated hinder border, which is very characteristic. The regular 

 curvature of the anterior and ventral borders is one of the chief 

 distinctions of the variety. 



Horizon and locality. — Roof-shales of the High Vein, Park- 

 field Series, Coalpit-Heath Colliery. 



