ANTHRACOMYA ADAMSII. 89 
1. Anroracomya Apamstr, Salter. Plate XII, figs. 1—19. 
AntHrRacomMya ApDAmsiIt, Salter. Geol. Surv. Mem. Iron OresS. Wales, 1861, p. 230, 
pl. ii, figs. 7, 7a, 7b. 
Non — — Ward. North Staff. Inst. Min. and Mech. Engineers, 
vol. x, 1890, p. 125, pl. i, fig. 2. 
_ — Hind. Quart. Journ. Geol. Soc., vol. xlix, 1893, p. 260, 
pl. viii, figs. 5, 5a, 6, 7, 8. 
Specific Characters.—Shell equivalve, obliquely and triangularly ovate, 
compressed all round the borders, and produced posteriorly. The anterior end 
is short, narrow in depth, only slightly convex, with a straight superior margin 
and a rounded border, the antero-superior angle being a rounded right angle. 
The inferior border descends rapidly, being at times slightly situated anteriorly ; 
otherwise the outline is more or less convex. The posterior end is flattened and 
expanded, with a more or less truncated border. The hinge-line is straight, 
extending nearly the whole of the length of the shell; its umbones are broad, 
tumid, contiguous, raised above the hinge-line, situated in the majority of cases 
at about a point equal to two-fifths of the length of the hinge-line from the anterior 
end. The posterior slope is much compressed, and produced upwards. An 
oblique obtuse swelling passes diagonally backwards and downwards from the 
umbo, and soon becomes lost on the surface of the shell, anterior to which is 
an almost obsolete broad suleus. The lunule is elongate and narrow. The carti- 
lage is external, very small and erect. The hinge-line has not yet been observed. 
The interior is smooth ; muscular scars normal in position and arrangement. 
The exterior is marked with fine excentric lines and folds of growth, which 
are crowded together at the anterior end, but diverge slightly as they pass across 
the shell, becoming parallel to the lower margin, the curvatures increasing in 
strength as they approach the posterior end, where they are reflected upwards to 
terminate in the superior border. Obsolete radiating lines are often seen on the 
posterior slope. Periostracum strongly wrinkled, shell thin. 
- Dimensions (Pl. XII, fig. 1): 
Antero-posteriorly : : : . 65 mm. 
Dorso-ventrally , : : . 45 mm. 
Laterally . : . 10mm. 
Localities—Soap vein, Pen-y-cae, South Wales. Little Mine ironstone of 
Fenton and Longton, which is the same bed known as the New Mine, or 
Burnwood, of the more northern part of the North Staffordshire Coalfield. 
Horsleywood seam, Northumberland. 
Observations.—Like other Coal-measure shells, the shape of Anthracomya 
Adamsii is not very constant even locally. The whole of the specimens of this 
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