78 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
this species may be of value in denoting a definite horizon. I have found it to 
occur all round the basin, from Hulme Colliery on the south-west, along the 
outcrop north-east to the foot of Mow Cop, and south-west by Talk-o’-th’-Hill 
to Halmerend ina bed some little way above the Cockshead Rock. Though found 
to have a fairly wide horizontal distribution, it does not appear to occur at 
more than one horizon. Although in no one specimen is the whole of the hinge- 
plate to be seen, yet, from many specimens where portions of it are to be seen, it 
appears to have a fairly regular character, resembling that of Carbonicola robusta. 
Portions of the hinge are seen in PI. XI, figs. 15, 25, and 26. 
The figure of Unio Castor, Eichwald, ‘ Letheea Rossica,’ 1855-9, pl. xxxix, 
fig. 20, somewhat resembles the species under description; but the latter is from 
beds of Permian age, and I have not been able to compare the shells, so that I 
cannot say whether the species are the same; but certainly Brown’s name has 
the priority. 
Prof. Amalizky (‘ Palzeontographica,’ vo]. xxxix, ‘‘ Ueber die Anthracosien der 
Permformation Russlands,” pl. xxii) gives figures of Naiadites subcastor, nov. 
sp., figs. 30—33 ; Naiadites Fischeri, nov. sp., figs. 34 to 39 ; and Naiadites Castor, 
figs. 40 to 43,—all of which show some resemblance to the adult forms of 
C. similis. 
Captain Brown’s description is as follows :—‘‘ Compressed, anterior side 
rounded ; umbones hardly produced, contiguous ; posterior side parallel, obliquely 
truncate; hinge-line straight, basal line arcuated; surface with transverse 
wrinkles.” Both the shells Unio similis and Unio nanus are from the same locality 
—Middleton, near Leeds. 
De Koninck gave the specific name Cardinia nana to a small fossil which 
Prof. Geinitz considers to be the same as that figured later on by Ludwig as 
Oyclas nanus ; and he states that the fossil in question is an Hstheria, and proposes 
that both should be placed in that group under the name of Hstheria nana (* Neues 
Jahrbuch fiir Mineralogie,’ &c., 1864, pp. 653-4 ; see above, p. 17). 
Specimens of Cardinia Scherpenzeeliana (de Ryckholt, 1850) approach, very 
closely in form the young of Bronn’s species, e.g. Pl. XI, figs. 10, 11, 13. 
15. CaRBONICOLA OUNEIFORMIS, sp. nov. Plate XI, figs. 24, 24a. 
Specific Characters.—Shell very oblique, moderately convex, wedge-shaped. 
The anterior end is small and compressed, but broad above. The shell rapidly 
becomes swollen in a posterior direction, and after attaining the maximum 
convexity is gradually compressed into the posterior border. 
The anterior border terminates abruptly above, forming a rounded slightly 
