ANTHRACOMYA LA‘VIS; Var. 125 
be the uncrushed form of his A. scotica. On this point it is impossible to give 
an opinion, as the original shell has completely disappeared. 
Mr. Etheridge, jun., drew attention to the close resemblance between Ludwig’s 
Anodonta obstipa and his species of A. scotica. This is very apparently so, but it 
is unsafe in the case of crushed and flattened shells to be too dogmatic. Ludwig 
shows that his specimen possessed a microscopically reticulated surface which, 
while it agrees with Dr. John Young’s prismatic cellular structure of Naiadites and 
other Mytiliform shells, also partakes of the character which Prof. T. R. Rupert 
Jones considers (‘Geol. Mag.,’ 1870, p. 217) “very unusual in molluses, but 
common in Hstheria.”’ 
Prof. Rupert Jones, however, later pointed out that Dr. John Young had demon- 
strated to him that shells in the genera Anthracoptera [| Naiadites |, Posidonomya, 
Pinna, Pteronites, Myalina, Aviculopecten, &c., possess a reticular punctate 
surface (‘ Trans. Geol. Soc.,’ Glasgow, 1890, p. 86), and he affirms the molluscan 
character of some shells previously considered to be crustacean. Judging 
from the figures and description, Cardinia Freystenii of Prof. Geinitz (* Die 
Versteinerungen der Steimkohlen-Formation in Sachsen,’ 1855, p. 2, pl. xxxv, 
fig. 7a, A) might be mistaken for A. levis, var. scotica, but it is somewhat larger, 
the measurements given being 15 mm. long by 11 mm. high. I can distinguish 
no other difference between this shell and the types of Mr. R. Etheridge, jun. ; but 
Professor Geinitz writes me that he now considers this shell to be an Estheria, and 
if this be the case of course there is no question of nomenclature involved ; but 
should this shell have been wrongly referred to Estheria, the specific name 
Freystenii is anterior to others. 
I have figured, Pl. XVI, fig. 23, an example of A. /evis from the South Joggins 
Coal-field of Nova Scotia, that it may be compared with the British forms. 
Fig. 20, Pl. XVI, shows an unusual character in the sinuosity of the posterior 
border just below the posterior superior angle, a condition more typical of the 
genus Naiadites. It is impossible, owing to the crushed state of the specimen, to 
pronounce with absolute certainty on the genus, but the general facies of the shell 
is that of Anthracomya levis, var. scotica, and not of Naiadites. 
A. levis, var. scotica, approaches A. Phillipsii more closely than other forms ; 
this may be, however, because both forms are met with crushed flat, and we are 
really almost in ignorance as to the contours of the shells. Both species were very 
gregarious, and though they existed for a long period, yet they had only a limited 
horizontal distribution. 
