264 Prof. T. R. Jones and Mr. J. W. Kirkby on the 



tliougli in others there Is no difference observable, and the ends 

 are about alike. 



In general form it has so much the character of recent Argil- 

 IcecicB that we place it in that genus, with the approval of our 

 friend Prof. G. S. Brady. 



It is not the same species as D'Eichwald's Bairdia ceqiudis, 

 which has more the appearance of a Bairdia. 



Arg. cequalis is essentially a Lower- Carboniferous form, 

 though it apparently occurs rarely in the lower beds of the 

 Carboniferous-Limestone series. 



Localities. Calciferous Limestone : Randerstone, Fifeshire ; 

 Linnhouse Water (opposite Oakbank Oil-works), Linlithgow- 

 shire ; Heads of Ayr, Ayrshire ; Larriston Quarry (New- 

 castletown), Roxburghshire ; Plashetts and Warksburn, 

 Northumberland. 



Carboniferous Limestone : Arnside, Westmoreland ; New 

 Rake, Grassington Mine, Yorkshire. Carboniferous-Lime- 

 stone series : Wilkieson ?, Fifeshire. 



37. Aglaia (?) cypridiformis^ J. & K. 

 (PI. IX. figs. 7 a, 7 h.) 



Cythere cypridiformis, J. & K,, MS. 1880, Quart. Journ. Geol. Soc. 

 vol. xxxvi. p. 588. 



Elongate-reniform, nearly of equal height before and be- 

 hind, valves moderately convex ; dorsal border very flatly 

 arched ; ventral border slightly incurved ; extremities rounded 

 and rather alike ; lateral contour elongate-oval, widest in the 

 centre ; right valve rather the largest ; surface smooth. 

 Length -^-^ inch. 



This rare species is confined to the Lower Carboniferous. 



Localities. Calciferous Sandstone : Randerstone, Fifeshire ; 

 Tweeden Burn, Roxburghshire; Glencartholm (River Esk), 

 Dumfriesshire ; Plashetts, Northumberland. 



38. Xestoleheris (?) suhcorbuhides, J. & K. 

 (PI. IX. figs. 8 a, 8^».) 



Xestoleheris subcorbtdoides, J. & K., MS. 1885, Geol. Mag. dec. 3, vol. ii. 

 p. 540. 



Elongate, suboblong, very tumid ; dorsal border flatly con- 

 vex, sloping at extremities ; ventral border straiglit ; extre- 

 mities rounded, the anterior least in height ; left valve larger 

 than right ; lateral contour ovate or obtusely cuneiform, and 

 of great width at posterior third ; shell thick ; surface smooth. 

 Length 3^5 inch. 



We refer this species to Xestoleheris, because it much re- 



