376 CARBONIFEROUS LAMELLIBRANCHIATA. 



Observations. — I have established this species on a series of six specimens in 

 the Museura of the Geological Survey of Ireland from the above localities. The 

 species appears to form a link between S. tricostatus and S. Omalianus, being 

 more gibbose and oblique than the former, and narrower from above downwards^ 

 and having its concentric markings much less well developed than the latter. 



The figure of de Koninck's ;S^. Portloclci may possibly be intended to represent 

 a shell of this species, and if so that name must of course have the priority ; but 

 as neither description nor figure sufficiently tallies with the Irish examples, I have 

 hesitated to refer them to this species. 8. PortJocM is stated to have three 

 radiating folds on the dorsal slope. The Irish shells have only one, beside the 

 main oblique fold. A single, very fine example of this shell has been found at 

 Castleton, Derbyshire (PI. XLI, fig. 1). 



Sanguinolites Walciodorensis, de Koninch, sp., 1885. Plate XLI, figs. 5 — 7. 



Ch^nomta Walciodoeensis, de KonincJc, 1885. Anu. Mus. Eo}-. Hist. Nat. 



Belgique, vol. xi, p. 8, pi. i, figs. 18, 19. 



Specific Characters.— '^\\e\\ of medium size, very inequilateral, transversely 

 ovate, obliquely gibbose, compressed in front and on the dorsal slope, somewhat 

 expanded posteriorly. Anterior end short, compressed, narrowed from above 

 downwards, projecting forwards with an elliptically curved border. The inferior 

 border is almost straight in front, but descends until it passes with a very large 

 curve into the posterior border. The latter is extensive, somewhat truncate 

 above, but bellying out below and rounded. The hinge-line is almost straight,, 

 somewhat shorter than the antero-posterior diameter of the valve, and raised 

 posteriorly, joining the posterior border at a more or less well-marked obtuse 

 angle. 



The urabones are tumid behind, compressed in front, incurved and twisted 

 forwards, close, elevated above the hinge-line, and placed in the anterior quarter 

 of the valve. From the umbones towards the postero-inferior angle the valve is 

 obliquely swollen, the gibbosity becoming rounded off into the compressed and 

 expanded dorsal slope. In front of the oblique swelling the valve is compressed 

 and hollowed by a broad and shallow sinus, the extreme anterior portion being 

 regularly (but slightly) convex. The lunule is large and long. The escutcheon 

 is long and narrow, separated from the dorsal slope by an erect ridge. 



Interior. — Unknown . 



Exterior. — The surface is covered with fine concentric lines and strise of 

 growth, which are much more marked in the neighbourhood of the umbo, and 



