Prof. T. Rupert Jones — Carboniferous Shale from Siberia. 435 



well-matclied in shape by our Fig. 10; but the latter is destitute 

 of the punctate ornament, and the former may be the young form 

 of a different species (P. sitbovata, nov.). 



The shell-structure in our specimens is not pitted nor clearly 

 prismatic, but is full of delicate lines of fissure, parallel with the 

 thick, radiating breakages, corrugations, or pressure-folds ; and 

 causing the shell to come away in subquadrangular pieces, which 

 are variously modified by decomposition before they are quite 

 removed from the internal cast. The straightness of the micro- 

 scopic fissures, and the regular edges of the separated pieces of 

 the shell, may be due to the presence of a crystalline or quasi- 

 prismatic structure not otherwise indicated. 



In Figs. 8-15, as also in Figs. 5-7, the vertical markings crossing 

 the concentric lines and riblets are due to pressure reducing the 

 convexity of the original shell. 



F. corrugata, R. Etheridge, jun. (Geol. Mag., 1894, p. 304, 

 PI. XIII, Figs. 4-6), occurring in the same shale at Linn Spout,^ 

 has a distant relationship with P. punctatella and subovata. Its 

 concentric lines, however, are crossed by rough cruraplings ; and 

 in its shape it differs from the other. Its variable and coarse 

 radial lines are evidently regarded by the author as congenital, 

 like the vertical ribs in P. costata, McCoy (Synop. Carb. Foss., p. 78, 

 pi. xiii, fig. 15), and, if the figures which he gives are of the 

 natural size, P. corrugata is much larger than Figs. 8-15. 



No. VI. Fig. 18 (Posidonoimja concinna, nov.). — This is part of 

 a larger Posidonomya, with numerous, distinct, narrow, concentric 

 ridges, with smaller parallel lines between. There are more perfect 

 specimens of this rotundo-ovate form in the collection, measuring 

 18 mm. vertically and 20 mm. transversely. 



This is characteristically abundant in some of the more solid shale 

 at the Toostooerr Eiver, accompanied by small Posidonomyce and 

 numerous obscure organic fragments. 



No. VII (Beyrichia Kirlcbyana, nov.). — Scattered throughout the 

 shales, especially those from the Boogtasch Mountain, are numerous 

 specimens of a small Beyrichia, about 1 mm. long. 



It is characterized by the two moieties of the valve being always 

 swollen, and separated by a dorso-medial sulcus, within and on one 

 side of which is a little tubercle ; and the whole surface is neatly 

 reticulate. 



This little Entomostracon is related to other Carboniferous 

 BeyricMcB, such as B. impressa (McCoy) and B. cratigera (G. S. 

 Brady). 



I propose to dedicate it to my lately deceased friend and fellow- 

 worker James Walker Kirkby, for whose work among the minute 

 fossils of the Carboniferous and Permian Series geologists owe great 

 thanks. 



1 Catal. "West. Scot. Fossils, 1876, p. 52. 



