ANTHRACOMYA L/EVIS ; 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. Ludwie" 

 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 molluscs, but 

 common in Estheria." 



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, Myaliua, Aviculopecten, &c, possess a reticular punctate 

 surface ('Trans. Geol. Soc.,' Glasgow, 1890, p. 8(3), and he affirms the molluscan 

 character of some shells previously considered to be crustacean. Judging 

 from the figures and description, Gardinia Freystenii of Prof. GeiDitz ('Die 

 Versteinerungen der Steinkohlen-Formation in Sachsen,' ]X.V>, p. 2, pi. xxxv, 

 fig. 7 a, a) might be mistaken for A. Items, var. scotica, but it is somewhat larger, 

 the measurements given being 13 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, PI. XVI, fig. 23, an example of A. l&vis from the South Joggins 

 Coal-field of Nova Scotia, that it may be compared with the British forms. 



Fig. 20, PI. 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 Igevis, var. scotica, and not of Naiadites. 



A. laevis, var. scotica, approaches A. PMllipsii 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. 



