110 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Cockshead Ironstone, Hulme Colliery, Longton. Ireland.—The roof of the 
Three-foot Coal, Bilboa, Queen’s County. 
Observations.—This species appears to be a rare form even in South 
Wales. It is quite distinct from A. pumila, from which its convex form at once 
distinguishes it. The position of the umbones even in Mr. Salter’s original figure 
hardly merits the epithet subcentral. I have, however, shown that the position of 
the umbones on the hinge-line is a varying factor in other species of this genus, 
and therefore do not regard such a character as of any value in specific 
determination. I figure, by the kind permission of the Director-General, three 
specimens, Pl. XVII, figs. 3, 4, 5, from the Three-foot Coal of Bilboa, Queen’s 
County, Ireland, which had been named Myacites fabeformis (Kinahan). These 
shells have all the characters of Salter’s A. subcentralis, to which I have now 
referred them. The hollow character of the compressed upper and posterior 
portion of the shell is well shown in all the examples. The blunt truncate 
posterior end is very characteristic. The specimens, Pl. XVI, figs. 5—8, from the 
Cockshead Ironstone are much crushed and distorted, figs. 7 and 8 having lost 
the anterior end by these means, but the hollow posterior slope and peculiarly 
truncate posterior are well marked. 
The best specimens of this species that I know are in the Collection of the 
Geological Survey, one from South Wales, the other from Bilboa, Queen’s County, 
Pl. XVUI, fig. 3. It is curious that the paleontologists in Ireland never seem 
to have adopted Mr. Salter’s genus for their shells, for, as far as I can trace, the 
genus Anthracomya has never been credited to the Irish Coal-measures until now. 
In the ‘ Geological Survey Memoir,’ “ The Iron Ores of Great Britain,” part 4, 
p- 294, Mr. Salter mentions the occurrence of A. subcentralis with A. pumila in 
the Knowles shale of the North Staffordshire Coal-field, but I know of no speci- 
men from these beds which can be in any way referred to this species. As far as 
is at present known, the forms A. Phillipsii and A. minuta are the only species of 
this genus which occur at this horizon. Iam unable to trace the original specimens 
on which these lists were founded, either in Messrs. Ward and Garner’s collections 
or in the collection of the Geological Survey, so that it is impossible to discover 
on what grounds the references were made. 
9. AnTHRACOMYA vBovata, Hind. Plate XVI, fig. 41. 
Anruracomya opovata, Hind. Quart. Journ. Geol. Soc., vol. xlix, 1893, p. 270, 
pl. x, figs. 22, 22a. 
Specific Characters—Shell obovate, inequivalve, the left valve being more 
convex. Anterior end almost obsolete, tumid, bluntly pointed. Posterior end 
