Palceozoic Bivalved Entomostraca. 37 



5. Carbonia secans, Jones and Kirkby. 



(PI. III. figs. 18-20.) 



Cythere secans, J, & K. Trans. Geol. Soc. of Glasgow, 1867, vol. ii. 

 p. 222. 



Mytiloid, compressed. Dorsal border arched, highest be- 

 hind, sloping rapidly in front to the anterior extremity, which 

 is pointed ; posterior extremity rounded ; ventral margin 

 slightly concave, with a small overlap of the right valve. 

 Dorsal and ventral aspects compressed ; the width is less than 

 one fourth of the length ; the height less than half the length. 

 Surface smooth. Length yL inch. 



This species is of comparatively rare occurrence. 



Localities and Mode of Occurrence. — Coal-measures : 

 Blakemoor, Wyre Forest, in ironstone, with C. fabulina 



&c. 

 Hylton, west of Sunderland, in ironstone, with C. Ranhiniana 



&c. 



Carboniferous Limestone series : 

 Craigenglen, Campsie, Lanarkshire, in impure limestone with 



C. fabulina. 



6. Carbonia jmng 'ens , Jones & Kirkby. 



(PI. III. figs. 21-23.) 



Cythere ptinyens, J. & K. Trans. Geol. Soc. of Glasgow, 1867, vol. ii. 

 p. 222. 



A small subcylindrical Carbonia, pointed at the anterior 

 end. Dorsal border flatly convex, highest behind, sloping 

 gently in front to a pointed anterior extremity ; ventral border 

 straight ; posterior extremity bluntly rounded. Height con- 

 siderably less than half the length. Dorsal and ventral 

 aspects cuneiform, being nearly as wide as high behind, and 

 acutely pointed in front. Muscle-spot situate rather anterior 

 to centre of valve. Surface smooth, so far as known. Length 

 TT6 inch. 



This species is the smallest of the series here described ; and 

 though somewhat resembling C. secans, it can be distinguished 

 by its general outline being less Mytiloid, and by its wedge- 

 shaped dorsal and ventral aspects. 



It is not a rare form in Scotch Carboniferous strata, but 

 is, as yet, of unknown occurrence in England. 



Localities and Mode of Occurrence. — Coal-measures : 

 Provanhall, near Glasgow, in black shale, with fossils as 



before. 

 Carluke, Lanarkshire, in ironstone, with fossils as before. 



