74 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



fragments is that of G. aquilina, showing the characteristic hinge-plate, which is the 

 form described by Professor King as occurring in A. Beaniana. This hinge-plate 

 has been necessarily modified from that occurring in other species of the genus by 

 the obliquity of the growth of the shell, and is anything but characteristic of the 

 genus, — in fact, I believe, from my observations, that it is peculiar to the species 

 C. aquilina. I made a special visit to the shell-bearing beds at Whitley, whence 

 Professor King obtained his original specimens, and was able to bring away with 

 me about 100 specimens, some of which I have figured, PL IX, figs. 10 — 24, a 

 series which shows the variable character of the shell. From a personal study of 

 Ludwig's original specimens, kindly permitted me by Professor Geinitz at Dresden, 

 I have no hesitation in saying that his Unio securiformis, Anodonta procera, 

 A. cicatricosa, and Unio crassidens are synonymous with Sowerby's G. aquilina, 

 and to this list Achepol has added no less than seven. 



Koenen's figures of Anthracosia securiformis are certainly typical of the species 

 under discussion. This author states that the originals of his figures are in the 

 Museum of Berlin. If so, there is no label to note that the specimen has been 

 figured, but I fully believe I saw the specimen there when I was permitted by the 

 authorities to study all the Coal-measure bivalves. The specimens in the Berlin 

 Natural History Museum labelled A. securiformis are certainly the same as those 

 I am figuring as G. aquilina, but they are very large forms, and have the edge of 

 the cardinal tooth facetted. 



Large forms are rare in England, but I figure one which occurred to me in the 

 roof of the Hard Mine at Hulme Colliery, Adderley Green, on PL XI, fig. 31 ; but 

 this is the only one which I have seen to attain these dimensions. 



The shells figured by Mr. John Ward, F.G.S. (op. supra cit.), possess none of 

 the specific characters of G. aquilina, and should, I think, be referred to C. acuta. 

 Mr. Ward has handed to me for figuring some shells of G. aquilina which have 

 several small circular holes scattered over them. These holes are so regular in 

 shape that they can scarcely have been due to erosion by plants, and so many that the 

 probability of the cause being due to boring by some gasteropodous mollusc may be 

 set aside. The edges of the apertures are everted, and it has occurred to me that 

 they may have been due to the bursting through the periostracum of bubbles of 

 C0 2 gas due to decomposition (?). Figures of two of these shells are given on 

 PL XI, figs. 32 and 33. 



The shell figured by Mr. Salter (op. supra cit.) as Anthracosia aquilina is very 

 characteristic in shape and excellently drawn, showing the specific details very 

 accurately. It is less elongated transversely, and has a comparatively greater 

 dorso-ventral measurement than obtains in the type, and thus is more akin in 

 shape to the form called by Professor King Anthracosia Beaniana. 



Localities. — England : Banbury ; Hard Mine, Bowling-alley Seam ; roof of 



