1862.] JONES FOSSIL ESTHERS. 145 



individuals of E. tenella yet met with (from Bradford Pit, Manchester) 

 Tiave not taken on the thickly striated valve-surface, such as is seen 

 in the other form. 



This Estheria was first noticed in the Autun shales*, regarded as 

 of Permian age by some (Geinitz), and as Upper Carboniferous by 

 others ; it was thought to be a small Posidonia (with some doubt) by 

 Michelin ; A. d'Orbigny, Landriot, and Naumann, however, regarded 

 it as being probably a bivalved Crustacean. Jordan found it again 

 in the Upper Carboniferous strata of the Murgthal, near Sulzbacb, in 

 the Schwarzwald, and, with Bronn, named it Posidonomya tenellaf. 

 This is also the species that occurs in the Brandschiefer of the Roth- 

 liegendes at Salhausen, near Oschatz, in Saxony J. I have it also 

 from the Upper Coal-measures at Astley and Bradford in Lancashire 

 (Binney and Salter), and from the Upper Coal-measures of Lanark- 

 shire (Mr. Grossart). Lastly, I am inclined to think that E. exigna, 

 d'Eichwald, from a Permian marl at Burakova, Russia, may possibly 

 prove to be the same§. 



E. tenella is a relatively small form, and often occurs in immense 

 numbers. In one instance (Astley, Lancashire) it is associated with 

 Beyrichice (B. subarcuata), of a form not far removed from the common 

 B. arcuata of the Coal-measures, but differing, in the less distinct 

 lobation of the valves, from the Lower Palaeozoic species. If this 

 Beyrichia were as truly marine as the Silurian Beyrichice proper, 

 E. tenella must have lived in salt water ; perhaps, on the other hand, 

 these associates were brought together, to the hurt of one or the 

 other, by the inroad either of salt or fresh water, respectively. Sjti- 

 rorbis again appears in company with Estheria (in Lanarkshire), and 

 may possibly indicate permanent sea- conditions, as must also Avicula 

 in the same locality, since it occurs as a participator of the same bed, 

 unless sudden changes of fresh and salt waters have left their effects 

 in one and the same deposit, or unless we are looking at the quasi- 

 marine fauna of an old brackish lake. Anthracomyce (Lancashire) and 

 Anthracosice (Lanarkshire) are also associated with E. tenella. 



4. Estheria exigua, Eichwald, sp., is known to me by a few very 

 small specimens on a little piece of Permian marl from Burakova, 

 Kazan, Russia, where it is found, with Plant-remains, in some 

 abundance. These specimens (sent by M. d'Eichwald) are not equal 

 to those described by Kutorga and d'Eichwald ; but they constitute 

 the only basis on which I can at present form an opinion. My 

 materials being limited, I keep this form distinct from E. tenella, to 

 which the Russian specimens (small as they are) present much 

 resemblance. If they belong to the same species, the name E. exigua 

 will have priority ; and, further, we have one more instance of com- 

 munity of specific forms in the Carboniferous and Permian deposits ; 

 indeed E. tenella itself proves as much, if the Permian character of 



* I have not seen specimens from this locality, 

 f Dr. Sandberger has sent me specimens. 



} Professors JNaumann and Geinitz have aided me with specimens. 

 § In which case the name given by d'Eichwald in 1846 would have priority. 

 I have not yet seen enough specimens from Russia to decide by. 



VOL. XIX. PART I. L 



