150 CARBONIFEROUS LAMELLIBRANOHIATA. 



Edmondia AM2ENA, de Koninck, 1885. Plate XXIV, figs. 1, 2. 



Edmondia ? am^na, de Koninck, 1885. Auu. Mus. Roy. d'Hist. Nat. Belg., torn. 



xi, p. 47, pi. x, figs. 1, 2, 6, 7. 

 Anthracosia eobusta. Mem. Geol. Surv. Scotland, Expl. sheet 22, p. 44. 



Specific diameters. — Shell of medium size, equivalve, inequilateral, transversely 

 suboval, gibbose. The anterior end short, its margin rounded. Inferior margin 

 convex; posterior margin obliquely truncate, bluntly rounded. Hinge-line very 

 slightly arched. Umbones large, tumid, incurved and twisted forwards, much 

 raised, placed about the junction of the anterior and middle thirds of the length of 

 the hinge-line. No lunule or escutcheon. Posterior end of the hinge-line elevated. 

 The valve is regularly swollen, except along the dorsal slope, which is so much 

 compressed as to be hollow. 



Interior. — The adductor scars are normal in position, very large, and much 

 roughened. The hinge-plate has a large spatulate process beneath the umbo. 

 Pallial line entire. Interior of valve immediately above it, strongly marked by 

 many close rough ridges and grooves at right angles to the line. 



Exterior. — Surface ornamented with fine concentric lines and striae of growth. 

 Shell thin. 



Dimensions. — PI. XXIV, fig. 1, a left valve, measures — 



Antero-posteriorly . . . .51 mm. 



Dorso-ventrally . . . .42 mm. 



From side to side (estimated from one valve) . 22 mm. 



Locality. — Calcareous shale, Burn Anne, Ayrshire. 



Observations. — Mr. J. Smith kindly sent me some shells which he had recently 

 obtained from Burn Anne, near Galston. They are found with Myalina and other 

 marine fossils. Some of the specimens occur as casts and show the adductor 

 muscle-scars and pallial line (PL XXIV, fig. 1). It may be noted thatde Koninck's 

 description of E. amsena does not suit his figures, two of which are not referred to 

 in the text. He says the umbones are small and almost terminal, whereas in the 

 figure they are much larger than is usual in the genus Edmondia, and not by any 

 means terminal. The Burn Anne shells have a much more pronounced dorsal 

 slope than is usual in Edmondia, and consequently have an elevated, almost erect, 

 upper border posteriorly. On referring to the list of fossils obtained by the 

 Geological Survey of Scotland from Burn Anne, locality 105, the horizon of the 

 beds being given as doubtful (op. supra cit., p. 44), the following fossils are said to 

 occur : Proclactus scabriculus ; Orthis resupinaia ; Aoiculopecten granosus ; Anthra- 

 cosia robusta ; A. oval is ; Axinus carbonarius ; Gtenodonta tjibbosa ; Myalina trian- 

 gularis; Bellerophon Urei; and Orthoceras, sp. 



