50 CARBONIFEROUS LAMELLIBRANCHIATA. 



Steeblopteeia oenata, R. Etheridge, jun., sp., 1873. Plate XI, figs. 10 — 12. 



Aviculopecten ornatus, B. Etheridge, jun., 1873. Mem. Gcol. Surv. Scotland, 



Expl. Sheet 23, p. 103. 

 Geol. Mag., vol. x, p. 346, 

 pi. xii, fig. 2. 



Sjiccific Characters.- — Shell of medium size, compressed, subcircularly quadrate, 

 inequilateral. The left valve more convex than the right valve. The anterior and 

 lower margins of the shell regularly rounded, the posterior almost straight and 

 oblique. The hinge-line straight and prolonged backwards, making a well-marked, 

 almost a right angle with the posterior margin. The umbo of the left valve large 

 and swollen, pointed and incurved, overlapping that of the right valve, which is 

 small, flattened, and not raised. The anterior ear small, triangular, and well 

 defined in the right valve ; depressed and somewhat rolled in the left valve. No 

 posterior ears, but the posterior superior angle of the valves flattened and 

 expanded in the form of a rectangular wing. 



Interior. — Unknown . 



Exterior. — The surface is ornamented with close, concentric lines, which are 

 crossed on the anterior side by fine, flexuous, radiating strise. The posterior wing 

 is almost smooth. The anterior ear of the right valve has a few well-marked 

 radiating ribs. 



Dimensions. — PI. XI, fig. 11, a left valve, measures- — 



Antero-posteriorly . . . .28 mm. 



Dorso-ventrally . . . .28 mm. 



Localities. — Scotland : the Lower Limestone series of Kinghorn, Fife ; Calder- 

 wood Limestone series of Waygateshaw Pit, Carluke ; between Avon Paper Mill 

 and Linlithgow Bridge ; River Gryfe, near Crosslea Mill, near Houston. Also, 

 according to Etheridge, the Upper Limestone series of several localities and 

 horizons. Ireland : the Carboniferous series of Fair Head, co. Antrim ; Rathkeale, 

 co. Limerick. 



Observations.— Mr. R. Etheridge, jun., founded this species and figured a right 

 valve {op. cit., 1873). The anterior ear of the type specimen seems to be detached ; 

 otherwise the figure of it is a good one. 



The absence of a posterior ear removes the species from Aviculopecten, with 

 which it has in other respects little or no affinity, and affirms its relationship to 

 Streblopteria. I have been able to study the left valve from specimens in the 

 collection of the Geological Survey of Scotland, which have been generously placed 

 at my disposal for the purpose. It is considerably more gibbose than the right 



