ANTIIRACOMYA 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, PI. XVI, fio\ 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 subcentrams, Salter, 18(31. Plate XVI, figs. 1 and 4—9 ; 



Plate XVII, figs. 3—5 ; Plate XIX, figs. 21, 21 a. 



Anthracomya subcentkalts, Salter. 'The Iron Ores of South Wales,' p. 231, 



pi. ii, fig. 9 a, 1861. 

 Myacites fab/f.formis, Kinahan. Geology of Ireland, pi. iv, figs, in, 4ib, ls7s. 

 Anthracomya subcentralis, Hind. Quart. Journ. Geol. Soc, vol xlix, p. 268, 



pi. x, figs. 30, 30 «, 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 \evj 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 Exterior. — 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, PI. XIX, in the Museum of the Geological Survey, 

 Jermyn Street, measures — 



Antero-posteriorly . . . .25 mm. 



Dorso-ventrally . . • .13 mm. 



From side to side . . • .10 mm. 



Localities. — South Wales : mine over the Three-quarters Coal, No. G Pit, 

 Victoria. The roof of the Hard-mine Coal, Mossfield Colliery, Longton. The 



