146 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Etheridge, jun., pointed out to be probably a dwarfed form of Myalina crassa, 
Fleming, a conclusion which I think to be probably correct. Naiadites obesa, 
Etheridge, and Naiadites crassa, var. modioliformis, have really little in common, 
and Mr. Etheridge does not, in his observation on the new species, mention any 
connection between them. 
I made a visit to the Fifeshire coast to obtain specimens, and Mr. Kirkby 
generously placed all his material in my hands, so that I have been able to 
examine a large number of specimens which I have compared with the originals 
of the figures of Mr. Etheridge’s Anthracoptera obesa, in the Museum of Science 
and Art, Edinburgh, and with a series of eleven specimens from Boness, kindly 
lent to me from the Geological Survey Collection of Scotland, which are doubtless 
the shells which served for Mr. Etheridge’s description; and after careful 
examination I have come to the conclusion that the Calciferous Sandstone shell and 
the Boness specimens belong to the same species. In the Calciferous Sandstone 
beds of the Fifeshire coast, Mr. Kirkby has shown that Naiadites obesa is found 
accompanied by several Ostracoda. Beyrichia subarcuata, Carbonia fabulina, 
C. subula, C. Rankiniana or bairdiodes, Leperditia Okeni: Cythere, sp.; Spirorbis ; 
Fish (Rhizodus) remains; a small Gasteropod; Littorina Scotoburdigalensis, 
Ktheridge, of doubtful genus, Carbonicola antiqua (Hind), and plant remains. 
In only one case, that of Zone 12 (op. cit., page 568) does Mr. Kirkby find this 
shell with typical marine forms, Lingula and Schizodus, but this bed of shale is in 
close contact with a limestone containing the usual fauna and flora which 
accompany N. obesa. No other fossil remains are said to occur with the shells in 
the Boness beds. 
Now that I have been able to see a large number of shells, I find that the 
specimens which I figured (op. sup. cit.) as Anthracoptera tumida from North 
Staffordshire are only very obese forms of N. cavinata (see p. 140, and Pl. XVIII, 
figs. 13, 14, and 16). In fact I have not met with this form out of Scotland. 
I have little doubt that Mr. Etheridge’s two forms are really the same species. 
It will be noticed in the original paper that he is somewhat in doubt as to the true 
genus of his shell, and places the mark ? after the generic name. In his observa- 
tions he points out that his shell closely resembles some forms of Myalina, from 
which he separates it because he saw no trace of the striated hinge-plate. It is 
very curious how completely this character is hidden when the fossils are embedded 
in matrix, or the two valves in proper apposition. 
By the kind permission of the Director of the Science and Art Museum, 
obtained for me by Dr. Traquair, I refigure one of the type specimens, Pl. XIX, 
fig. 16; but it differs much from the other figures given of the same shell. This is a 
full-grown and large example, and many shells of the same size occur in the shore 
beds opposite Kilrenny Mill, Fife, while those like the other type figures are common, 
