110 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



Cockshead Ironstone, Hulrae 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, PI. XVII, figs. 3, 4, 5, from the Three-foot Coal of Bilboa, Queen's 

 County, Ireland, which had been named Myacites fabseformis (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, PI. 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, 

 PI. XVII, fig. 3. It is curious that the palaeontologists 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. 204, 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. I am 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. 



'.». Anthracomya obovata, Kind. Plate XVI, fig. 41. 



Anthracomya obovata, Hind. Quart. Journ. Geol. Soc, vol. xlix, 1893, p. 270, 



pi. x, figs. 22,22 a. 



Specific ('liararlrrs. — Shell obovate, inequivalve, the left valve beiug^more 

 convex. Anterior end almost obsolete, tumid, bluntly pointed. Posterior end 



