64 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
of the Earth,’ pl. ii, fig. a. I have unfortunately not been able to see any 
specimens from the given Scotch localities, and therefore cannot state anything 
about the probable nature of the shell, and I have thought it best to invent a new 
term for the species under notice. I have had the pleasure of examining two 
specimens, which I here name C. nucularis, from Dunfermline, in the Braid- 
wood Collection of Dr. Hunter, although they are somewhat different from 
my other examples. As far as I know, the species has a limited horizontal 
and vertical range, and I can only quote three localities. In the Hard-mine 
roof in North Staffordshire, whence I have obtained about fifty specimens, it 
occurs with C. aquilina, Anthracomya Williamsoni, and three forms of Naiadites, 
and in about the same proportion as A. Williamsoni, both being markedly less 
frequent than the associated shells. 
I have figured a series from this bed in order to show the amount of 
variation which occurs. All my specimens have been gathered in about one 
square mile, with the exception of figs. 30 and 31, Pl. VII. 
The blunt posterior end seems characteristic. This form is not met with of 
greater size than fig. 25, Pl. VII; and specimens as large as this are by no means 
common. If the hinge-line be carefully examined in many, there will be noted a 
slight S-shaped curve between the umbones, indicating cardinal teeth, the curve 
showing the right cardinal tooth to have been anterior. ‘This sinuation is so very 
shght that in some shells it may be easily overlooked. I have never found any 
testiferous specimens in the south-east end of the coal-field. The two figs. 30 
and 31 come from beds of the same horizon at Talk-o’-th’-Hill. I was fortunate 
enough, among the specimens from the Mountain Mine of Wigan, sent me by 
Mr. Waring, to find one in which the valves had slipped, so that the anterior part 
of the hinge-plate was seen. I did not think it necessary to figure it, as I had 
before figured specimens showing the normal plan of the hinge apparatus, Pl. V, 
fig. 1, as it occurs in C. ucuta. 
The specimens from Wigan and Leicestershire show very fine lines of growth 
indeed, and the same condition is very apparent (in the testiferous specimens 
figured) beneath the much-wrinkled periostracum. 
In the Cardiff Museum I have noted a series of four which retain the shell and 
periostracum. They are truncate forms, like those figured in Pl. VII, figs. 36, 40, 
and 41. Unfortunately the horizon at which they occurred in the South Wales 
Coal-field is not stated. 
The shell is more tumid and regularly swollen for its size than any other form, 
and the umbones are lower and less pronounced. 
