CH^NOCARDIOLA FOOTII. 475 



the same time I do not agree with Beushausen's orientation of the shell, and have 

 no doubt that the short, obliquely truncate end is posterior. Under these 

 circumstances Beushausen's description will need revision. I am not at all clear 

 as to the real affinities of Ghsenocardiola, though there is a certain resemblance to 

 Conocardium, and further material is necessary for study before any more definite 

 statement can be made. I am, however, of opinion that the genus is more nearly 

 related to the Gardiidse. One species occurs in British Carboniferous rocks, in 

 the Coal Measures both of Ireland and England, and as far as I can ascertain at 

 present at a single horizon in each country. 



Beushausen states that the genus Ghmnocardiola occurs first in Upper Silurian 

 rocks, and exists in the Middle and Upper Devonian ; it would now appear that it 

 did not die out till Coal Measure times. 



Ch/Enocakdiola Footii, Baily, sp., 1860. Plate LII, figs. 5 — 7. 



LuNULACAEDiuM FooTii, BoUy, 1860. Expl. Sheet 142, Geol. Surv. Ireland, 



p. 19, fig. 9 a — e. 

 Conocardium Footii, Etheridge, 1888. Brit. Foss., pt. i, Palseozoic, p. 281. 



Specific Gharacters. — Shell of moderate size, oblique, triangularly semilunate, 

 slightly convex, truncate behind. The anterior end is comparatively large, and 

 projects in front of the umbo, compressed at margin, rounded, continuous with 

 the curved inferior border, which is bent rapidly upwards at its posterior extremity 

 to join the straight, oblique, posterior border at a well-marked angle. The 

 hinge-line is short and curved, especially in front. 



The umbones are small, pointed, incurved, and twisted forwards, elevated 

 above the valve. Passing downwards and backwards from the umbones to the 

 postero-inferior angle is a well-marked ridge, behind which the valve is rapidly 

 compressed, forming a narrow but long and oblique dorsal slope. In front of the 

 oblique ridge the valve is regularly but gently curved. 



Interior. — I have described the internal characters of the genus from this 

 species, and need not repeat the description here. 



Exterior. — The surface is covered by concentric lines and ridges of growth, 

 which are crossed by well-marked, strong, not numerous, radiating ribs. At the 

 margin where the concentric lines are stronger, the ribs have well-marked 

 crenulations, but these are not so distinct above. 



Dimensions. — PI. LII, fig. 5 h, one of the types of Baily's species, measures — 

 Antero-posteriorly . . . .26 mm. 



Dorso-ventrally . . . .24 mm. 



Localities. — England : Coal Measures, Burnley, Lancashire. Ireland : Coal 



