102 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



I bad the opportunity, for which I thank Professor Geinitz, of examining the 

 originals of his Anthracosia Weissiana, from the Saarbriicke Coal-field in the 

 Dresden museum (op. supra cit.), and have no hesitation in referring that shell 

 to the British form. Achepol's Anthracosia Harzi, from the Hannebal group 

 Bochum, is doubtless the same shell ; and, if I am correct in my surmise that the 

 Russian form is also identical, it is interesting thus to trace the shell right across 

 Europe. 



Judging from the description of Pleurophorus subcostatus of Messrs. Meek and 

 Worthen, I think it highly probable that their shell belongs to the species under 

 discussion. I have quoted from their description antea, p. 87, to show that they 

 lay stress on some of the characters which I consider typical of Anthracomya. It 

 is said to occur in the Upper Coal-measures of Gallatin County, Illinois. 



The Anthracosia Harzi of Achepol is, I think, a specimen of A. Williamsoni ; 

 curiously enough, this shell is not figured in the body of the work as a photograph, 

 but is only in a supplement, which consists of a series of engraved figures of the 

 shells previously described, but it is not stated if the shells are drawn from real 

 specimens or are from restorations, and intended to give a general indication 

 of the size and shape. 



Anthracomya Williamsoni varies very much in the shape of the posterior end 

 and in its comparative measurements. At times the posterior border is truncate, 

 at others bluntly rounded, or the inferior angle may be at times somewhat prolonged, 

 so that it may become a right angle or even slightly acute. Many specimens show 

 a typically gaping posterior end, and as many, on the other hand, have the valves 

 close all round. I have not been able to satisfy myself that there has been any 

 dislocation of the valves or eversion of the shell due to pressure or injury in those 

 specimens which gape, and am inclined to believe that in some individuals the 

 valves gaped and in others the valves were closed. The same conditions are to 

 be observed in the marine fossil Sanguinolites (?) sulcata, the Sanguinolaria sulcata 

 of Phillips, from the Redesdale ironstone, some specimens of which shell appear 

 to have widely gaping posterior ends, and others to be closed all round. 



In my notes made at the Natural History Museum of Brussels I have it that 

 the specimen labelled there Mytilus prsepes, de Ryckholt, is the same species as 

 A. Williamsoni. The original drawing does not, however, show a very close 

 resemblance, but the description is fairly characteristic. The original specimen 

 was from the coal shale of Mons, the one I saw was from Longchamps. 



