64 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



of the Earth,' pi. 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 G. 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, PI. VII. 



The blunt posterior end seems characteristic. This form is uot met with of 

 greater size than fig. 25, PI. 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 

 slight 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, PI. V, 

 fig. 1 , as it occurs in C. acuta. 



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 PI. 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. 



