Palceozoic Bivalved Entomostraca. 263 



Fig. 3 is a right valve, showing a flat marginal area, wider 

 behind than before. 



This species is doubtfnlly referred to Cytherella. It was 

 collected by Mr. Bennie in the Carboniferous-Limestone series 

 at Murrayfield (Bathgate), Linlithgowshire. 



34. Bythocythere antiqua, sp. nov. 

 (PI. IX. figs. 5 a, 5 b.) 



Subrhoraboidal in outline, tumid ; dorsal border nearly 

 straight ; ventral border convex ; anterior extremity subtrun- 

 cate and projecting below ; posterior extremity flatly rounded 

 and projecting above. Valves apparently equal, and with a 

 ventral expansion or wing, as in the recent Bythocythere and 

 CytheroiHeron^ which is most developed posteriorly ; lateral 

 contour subovate with pointed ends, greatest width about the 

 posterior third ; surface pitted, pits shallow, rather large, and 

 wide apart. Length -g-\j- inch. 



We have two examples of this interesting species from Mr. 

 G. R. Vine, of Sheffield, who obtained them from the Lower 

 Carboniferous of Skellygate (Ridsdale) , Northumberland. 



35. Bythocythere Youngiana^ sp. nov. 

 (PI. IX. figs. 4 a, 4 ^».) 



This is a smaller species than that just noticed, and less 

 angular in outline. The ventral wings also are relatively 

 smaller ; the lateral contour of regular width throughout 

 (compressed-oval with pointed ends) ; and the surface is more 

 closely and regularly pitted. It is -^j^ inch in length. 



It was discovered by Mr. John Young in the Carboniferous- 

 Limestone series, at Brockley, Lanarkshire. We have also 

 met with it in a washing of shale from Woodend Quarry, 

 Lowick, Northumberland, kindly sent us by Mr. James 

 Bennie. 



36. ArgilloBcia cequalis, J. & K. 

 (PI. IX. figs. 6 a, 6 h.) 



Argilloecia cequalis, J, & K., MS. 1885, Geol. Mag. dec. 3, vol. ii. p. 540. 



Elongate, compressed, nearly equal in height thoughout, 

 and with equal ends ; dorsal border flatly arched ; ventral 

 border straight or slightly convex ; anterior extremity rather 

 higher and less projecting than the other ; lateral contour 

 elliptical, widest in the centre ; right valve largest and over- 

 lapping the left ; surface smooth ; shell thick. Length 

 '25 to Y2 inch. 



In most specimens this species is a trifle highest in front ; 



