ANTHRACOMYA SUBCENTRALIS. 109 
distinct. A. pumila may be distinguished from A. pulchra by the flattened 
compressed form, and the absence of the well-marked escutcheon posteriorly. 
In my paper of 1893, op. sup. cit., I erroneously referred a specimen from the 
Strickland Collection in the Woodwardian Museum, Pl. XVI, fig. 40, to a new 
genus erected on two specimens which I now recognise as distinct. The one 
specimen agrees closely with many other forms from the South Wales Coal-field. 
8. ANTHRACOMYA SUBCENTRALIS, Salter, 1861. Plate XVI, figs. 1 and 4—9; 
Plate XVII, figs. 3—5; Plate XIX, figs. 21, 21a. 
ANTHRACOMYA SUBCENTRALIS, Salter. ‘The Iron Ores of South Wales,’ p. 231, 
pl. u1, fig. 9a, 1861. 
Myacrres rapxrormis, Kinahan. Geology of Ireland, pl. iv, figs. 4a, 4b, 1878. 
ANTHRACOMYA SUBCENTRALIS, Hind. Quart. Journ. Geol. Soce., vol. xlix, p. 268 
pl. x, figs. 30, 30a, 1893. 
? 
Specific Characters.—The shell is transversely oblong, markedly convex. The 
anterior end is rounded, tumid, somewhat prominent and deep dorso-ventrally. 
The inferior border is almost straight, the posterior inferior angle bluntly rounded. 
The posterior border is bluntly rounded, and the posterior superior angle 
is well marked and slightly obtuse. The hinge-line is straight and almost 
parallel to the inferior border. The umbones are very obtuse and tumid, hardly 
marked off from the general gibbosity of the shell; the apices are acute, incurved, 
and pointing slightly forwards. They are situated about the junction of the 
anterior and middle thirds of the length of the shell. The lunule is well marked. 
The valves are evenly swollen in an oblique direction from the umbones to the 
posterior inferior angle, above which the shell is much compressed into the hinge- 
line, so that it is often slightly concave. The ligament is external, very short, 
and not much elevated, and there is a long narrow groove on each side of it 
representing the escutcheon. 
The Interior is unknown. 
The Hxterior.—The surface is almost smooth, but is marked towards the ventral 
border by well-defined lines of growth. The periostracum is wrinkled. 
Dimensions.—Fig. 21, Pl. XIX, im the Museum of the Geological Survey, 
Jermyn Street, measures— 
Antero-posteriorly . : : . 25 mm. 
Dorso-ventrally : : : =) Seman: 
From side to side ; : ; «10mm. 
Localities.—South Wales: mine over the Three-quarters Coal, No. 6 Pit, 
Victoria. The roof of the Hard-mine Coal, Mossfield Colliery, Longton. The 
