54 Prof. T. R. Jones and Mr. J. W. Kirkby on 



genera. Bcyrichia umhonata and B. stn'olata seem to belong 

 to Kirkhyn ; and Bairdia hvvigata is a Leperditia. 



Soon after tlie ])ublieation of the above-named work we 

 were kindly favoured by ^I. d'Kiehwald witli a series of 

 Russian spociniens ; and these have euaV»k'd us to arrive at 

 a better untU-rstanding on some points of his (^arlx)niferons 

 species. We have also some other speeimeus, brought from 

 Russia by the late Sir Roderick 1. Murchisun. Out of the 

 eight species and their varieties (four) which we have identified 

 among our Russian specimens, four have already been described 

 as Carboniferous, two as Permian forms, one as Silurian, and 

 four are new. Three or four named by M. d'Eiehwald we 

 relegate to other authors. There remain six or seven of M. 

 d'Eichwald's Carboniferous species which we have seen in 

 figures only. 



^ye figure the best of our Russian specimens in Plate VI. ; 

 and the following observations will assist in defining the 

 species. 



1 & 1*. Leperditia Okeni (Von Minister f), and var, inornaia 

 (M'Coy). PI. VI. figs. 1 .t 2. 



Bairdia Iccvigata, var. nignsccns, D'Eiehwald, Leth. Ross. i. vii. p. 1342, 

 pi. 52. tig. o. 



This species, so common in the Carboniferous formations of 

 Britain, Europe, and Nova Scotia, occurs in great numbers 

 in a piece of hard, dark-grey, saccharoid limestone, labelled 

 "Bairdia kevigata, var. nigrescens, village of Phillinconowa, 

 in the Government of Toula." The specimens, rather small, 

 are all single valves, and of a blackish colour. The general 

 contour of the carapace is nearly that of the typical L. Okeni. 

 The eye-spot is not distinguishable. Primitia Eichicaldt, 

 Corals, and Brachiopods are associated. 



From near Likhwine, in the same Government, we have a 

 minute specimen of this species, with a well-marked eye-spot 

 and a slight marginal rim (fig. 2). In the former feature it 

 agrees with M. d'Eichwald's figure of his "Bairdia Ja^vigatay 

 From the same locality, in a piece of soft yellow limestone, 

 otlier rather larger specimens occur, which wo, also refer to 

 this species. They differ in Iiaving the carapace-valves less 

 oblique than is usual with L. Okeni, thus having a nearly 

 semicircular hinder end. These might without much dif- 

 culty be mistaken for a Oythere, and indeed do occur in a 

 ])iece labelled "Bairdia excisa^ This variety is not unusual 



t Ann. .t Ma- Nat. Hist. ser. •% vol. xv. p. m\ pi, 20. figs. 1-0. 



