170 EXPLANATION OF PLATES. 



EXPLANATION OP PLATE X. 



Fig. 1 Cythere (Ci/therldeis) Jonesiana, Kirkby : right valve, magnified 30 



diameters. 



2 C. Jonesiana: a less elongate form, right valve, magnified 30 



diameters. 

 2a C. Jonesiana: lateral contour. 



3 & 3a Bairdia rhomhoidea, Kirkb}' : right valve, magnified 26 diameters. 



4 & 4a Cythere amjmtata, Kirkby: cast of left valve, magnified 38 diameters, 



figured with the ventral border upwards. 

 5 Kirhbya Permiana^ Jones : right valve, having a smooth surface 



magnified 26 diameters. 

 6 & 8... K. Permiana : right and left valves, showing a 

 7 K. Permiana: left valve of a specimen, showing the reticulation of 



surface, magnified 30 diameters. 

 9 K. Permiana: left valve of a young specimen, magnified 38 



diameters. 

 10 & 11 K. Permiana : ventral aspects of two specimens, magnified. 



12 K. Permiana: dorsal aspect, magnified. 



13 K. Permiana: interior of right valve, magnified. 



All from the shell-limestone of Tunstall Hill. 



EXPLANATION OF PLATE XL 



All the figures are magnified 25 diameters, excepting fig. 19/. 



Fig. la, Cythere Morrisiana, Jones: right valve— 16, edge- view ; Ic, end-view of 



carapace. 

 2, Cythere Elongata^ Munster : right valve. 

 3a, Cythere Kutorgiana^ Jones: showing cast of the left valve, and edges of 



the right ; 36, larger specimen, showing cast of the right valve, and 



edges of the left. 

 4a, Cythere Geinitziana, Jones : left valve — 45, profile ; 4c, end-view. 

 5a, Cythere biplicata, Jones : showing cast of the right valve, and the edges 



of the left; 56, a larger specimen, with the plication modified; left 



valve. 

 6, Cythere inornafa, M'Coy : left valve. 

 7a, Cythere nucijormis, Jones : right valve — 76, edge-view of carapace ; 7c, 



end-view. 

 8, Cythere (Bairdia) pleheia^ Reuss : right valve. 

 9a, brevicauda, Jones : 96, profile of carapace ; 9c, end- 



