CARBONICOLA ACUTA. 53 



Bowling Alley, over Four-foot Coal, Wetley Moor; N. Staffs Coal-field; above the 

 Broach Coal, Dudley; Middle Coal-measures of Bolton, Bury, and Oldham; Coal- 

 measures, Nottingham ; Unston, Derbyshire. South Wales : Rosser Vein, Cwm 

 Bryn ddu, Jack mine, Cwm Aman. Blue Vein, Gantre ; Bottom Vein, Sirhony. 

 Stanley Main ; Wakefield ; Sheden ; Lowmoor, Middleton ; Band, near Townelly 

 Seam, West Wylam. Eltingham Colliery, Prudloe ; Northumberland and Durham 

 Coal-field. Scotland: Kilmarnock; Shotts; Airdrie, Shettleston, U. C.-m.; Eight- 

 foot Coal, Scoonie ; roof of Eight-foot Seam, Durie Colliery ; Fifeshire Coal-field. 



Observations. — This species has a wide distribution, both horizontally and 

 vertically. Its form, however, as might have been expected, varies considerably. 

 The type form (Sow.), PI. Ill, fig. 1, is perhaps the most common, but the varieties 

 do not seem to be due to local or horizontal environment. I find them all occurring 

 in numbers in the roof of the Cockshead Seam of the North-Staffordshire Coal- 

 field, with members of an intermediate form, indicating the lines of variation. In 

 many specimens there exists a feature denied to this species by M'Coy, namely, a 

 subconstriction or oblique sulcus, widening as it approaches the ventral border, 

 and showing a close relationship to similar forms of G. robusta, with the smaller 

 elongated form of which shell, indeed, G. acuta is closely allied, differing chiefly 

 in the relatively smaller dorso- ventral and lateral measurements. 



M'Coy relied on " the lengthened form, straight insinuate ventral margin, the 



side without any oblique concavity, as well as the greatest width [dorso- 



ventral] being a little behind the beak, instead of from the apices," as charac- 

 teristics of this species ; yet, while many shells agree with this description, one or 

 other of these characters often varies. 



I think, with M'Coy, that the forms described and figured by Brown (op. cit. 

 supra) as Pachyodon, and Vnio exoletus, antiquus, transversus, and Levidensis, are 

 forms of this species ; and to these I would add the forms Pachyodon and TJnio 

 agrestis ; but it is impossible to judge accurately from drawings only, and the 

 original specimens have entirely disappeared. Yet, from other localities, I know 

 examples of these forms which I consider to belong to this species. 



I am disposed to regard, from inspection of the figures and Goldfuss's descrip- 

 tion, TJnio tellinarius as an example of this species. De Koninck appears to have 

 copied Goldfuss's figure, but it is difficult to be certain as to identification, as 

 the original specimens have disappeared. 



M'Coy thought that his Carbonicola subconstricta was synonymous with the TJnio 

 and Pachyodon tellinarius of the above authors. 



Fleming has curiously enough (' History of British Animals,' p. 417, 1828) 

 referred TJnio acutus, Sowerby, to the Middle Oolite ; but this must be an error, 

 for Sowerby gives " Bradford," Yorkshire, as the locality of this shell. 



I have been permitted by the kindness of Dr. H. Woodward to figure the 



