common to Carboniferous and Permian Strata. 203 



marine shales and limestones of that district. The Permian 

 fossils with which they have been compared are from the Mag- 

 nesian Limestone of Durham. Two of the species are Ento- 

 mostraca of the subgenus Bairdia ; the other is a Polyzoan of 

 the genus Fenestella. 



1. Cy there (Bairdia) plebeia, Reuss, 1854. 



Permian specimens, PL IV. figs. 7,8, 10; Carboniferous speci- 

 mens, PI. IV. figs. 5, 6, 9. 



Type-specimens of B. plebeia are moderately inflated, have a 

 subdeltoid carapace, a lenticular lateral contour, and smooth 

 surface. The posterior extremity is more or less acute and ros- 

 trated ; the anterior extremity is much deeper and rounded. It 

 is a species, however, that possesses considerable latitude of 

 form, nine varieties having already been described by Mr. T. R. 

 Jones and myself*. 



The Carboniferous Entomostraca which are identified with 

 this species agree in all the above characters, as well as in others 

 of minor importance. This, I think, will be evident from the 

 figures given of specimens from both formations. 



The Carboniferous specimens, which do not seem to have 

 been hitherto noticed, occur in dark-grey shale at Craigenglen, 

 Campsie. 



2. Cythere (Bairdia) Schaurothiana, Kirkby, 1858. 



Permian specimens, PL IV. figs. 3, 4, 12 ; Carboniferous speci- 

 mens, PL IV. figs. 1,2, 11. 



B. Schaurothiana is a larger Entomostracan than the pre- 

 ceding species. It is somewhat elongate and almost subhexa- 

 gonal in outline ; the posterior extremity is angulate, and not 

 much produced, its upper half being formed by an abrupt de- 

 scent of the dorsal margin ; the anterior extremity is broad, 

 rounded, and at times subangulate above ; the lateral contour is 

 more or less lenticular, and the surface is smooth. 



The Carboniferous specimens which I place with this species 

 are generally of larger size and more robust than Permian ex- 

 amples ; and in some specimens the ventral margin anteriorly 

 becomes more prominent than I have ever seen it in Schauro- 

 thiana, but this is probably concomitant with an increase of 

 development. In all essential particulars they agree with the 

 characters of the species to which they are referred, there being, 

 so far as I can observe, no point of specific difference between 



* Trans. Tynes. Nat. Field Club. vol. iv. pp. 141-146 and 161, 162. 



