CARBONICOLA ROBUSTA. 47 



near Ayr, Dalmellington, Airdrie, Cummock and Shotts, and above the Drumgray 

 Coal of Lanarkshire. England : Lower yard seam, Fulledge Colliery, Bnrnley. 

 Above the Arley Mine, Lancashire. Middle Coal-measures, Pendleton, Lancashire. 

 Lofthouse and Killingback-beds, near Leeds. Roof of Shale Coal, Wakefield. 

 Brockwell Seam, Wylam, Northumberland. Above the Holly Lane and Bowling 

 Alley, and 10-foot Seams. Shale above 4-foot Coal, Wetley Moor. Shale above 

 Woodhead Coal, Froghall, all in the Lower Coal-measures of North Staffordshire. 

 Coalbrookdale (Pennystone Beds). Alfreton, Tibshelf (small form), and Codnor 

 Park, Derbyshire. 



Observations. — Through the kindness of Prof. Prestwich I have been able to 

 study and figure the original type-specimen, PL I, figs. 2, 2 a, which apparently 

 differs widely from Salter's type : but it was pointed out to me by Mr. H. Bolton, of 

 the Manchester Museum, Owens College, that Prof. Prestwich's shell was crushed 

 and incomplete, as was, indeed, shown in the original drawing, the lines of growth 

 terminating abruptly without becoming reflected upwards to the superior border. 

 A smaller form, PI. II, fig. 3, kindly lent me by Dr. John Young, of Glasgow, 

 approaches somewhat to the original figure, its posterior end not being developed. 

 This I believe to be a young state of the shell, from the fact that a series of inter- 

 mediate specimens can be shown. PI. I, fig. 6, from the Braidwood Collection of 

 Dr. Hunter, and PI. II, fig. 3, another of Dr. J. Young's specimens, are such forms. 



De Koninck's figure of this shell (' Les Animaux Fossiles de la Beige,' pi. ii, 

 fig. 1) is like Dr. John Young's small specimen ; but this species seems to be rare 

 in the coal-fields of the Continent, as no other author, except perhaps Achepol 

 (' Niederrh.-Westf . Steinkohlen-Gebirge, Atlas,' Suppl. 1, figs. 19, 20, A. crassa ; 

 and Suppl. 3, A. caudata), records its presence; and, except at Brussels, I have 

 seen none in any museum abroad. M'Coy (' British Palasozoic Fossils,' p. 515), 

 judging from Sowerby's figures of Unio subconstrictus ('Min. Conch.,' Tab. xxxiii, 

 figs. 1 — 3 ; and U. robustus, ' Trans. Geol. Soc.,' ser. 2, vol. v, pi. xxxix, fig. 14), 

 considered that the latter was only an adult form of the former, the figure of 

 U. robustus appearing shorter and deeper than natural from the oblique fracture of 

 the posterior end. 



I have not seen very many hinge-plates of G. robusta ; but, judging from those 

 I have seen, this species seems to have possessed a more constant form than 

 others. Mr. Salter figures a hinge-plate in the Appendix to the ' Geological 

 Survey Memoir, the Country round Wigan,' which agrees very closely with 

 PI. II, fig. 9. In young forms the anterior part of the hinge-plate does not seem 

 to be developed into a cardinal tooth to the extent which obtains in older 

 specimens. In Salter's figure there is a little irregularity shown in the hinge- 

 plate towards the posterior end : I have seen a similar condition in some of the 

 interiors of other species of Carbonicola, and consider it to be the position of the 



