them to Mr. T. Davidson, F.R.S., who was kind enough to favour me with the following reply to my letter:—"As you say, one or two of them look like a small variety of L. squamiformis. This last is, however, a much larger shell; and I would almost feel inclined to refer them to L. mytiloides." The present individuals so closely resemble those, that, although they are in any thing but a good state of preservation, I do not hesitate to refer them to the same species.
Loc. and Horizon. In hardened shale, quarry under Craiglockhart Hill, as before; in shale with other marine fossils at Woodhall Mill, as before; in shale above the sandstone at Craigleith Quarry, near Edinburgh.
Class PELECYPODA (LAMELLIBBANCHIATA).
Genus Avicula, Klein.
Avicula Hendersoni, sp. nov. Pl. I. fig. 11.
Sp. char. Obliquely transversely elongated, very inequilateral. Anterior end well marked, divided off by the byssal sinus; posterior end produced, obtusely rounded; posterior wing flattened, falciform; hinge-line straight, not so long as the shell; ventral margin subparallel with the hinge-line, indented by the byssal notch, otherwise convex. Posterior slope well marked, obtusely rounded; byssal sinus extending from the beak as a pronounced groove in each valve; widening towards the ventral margin. Umbones anterior, prominent. Surface of both the body of the shell and the posterior wing covered with very regular concentric imbricating striæ.
Obs. Avicula Hendersoni is closely allied to several Irish species figured by Prof. M'Coy[1], and seems to be nearest to his A. angusta, but with the dorsal and ventral margins much more nearly parallel than in the latter, in this respect corresponding more closely with A. recta, M'Coy, and A. gibbosa, M'Coy, from which, however, it otherwise differs considerably. I name the species after Mr. Henderson, to whom I am indebted for the loan of the majority of the specimens described in this communication.
Loc. and Horizon. In a hard Cyprid shale, quarry on the north side of the Colinton road, under Craiglockhart Hill, near Edinburgh, near the base of the Cement-stone group; in shale with marine fossils at Woodhall, as before.
Genus Aviculopecten, M'Coy.
Aviculopecten, M'Coy, 1851, Ann. & Mag. Nat. Hist. vii. p. 171.
Aviculopecten, sp.
Obs. A portion of one valve has been obtained from the Woodhall Shale, It is a radiately striated species, with the ribs crossed by
- ↑ Synop. Carb. Foss. Ireland, t. xiii. f. 20.
