Page:Quarterly Journal of the Geological Society of London, vol. 34.djvu/33

Rh

Spirorbis, Lamarck, 1818, Hist. Nat. Anim. sans Vertèbres, v. p. 358.

, Murchison. Pl. I. figs. 1 & 2.

Microconchus carbonarius, Murch. Sil. Syst. 1839, p. 84, f. D 1–10.

Spirorbis carbonarius, Murch. Siluria, 1867, 4th ed. p. 302, Foss. 83.

''Sp. char.'' Tube attached by one side, forming a more or less closed helix of from 1$1⁄2$ to 3 turns, not all in the same plane, increasing in size slowly towards the aperture, and dextral; umbilicus deep; aperture oval or circular, sometimes extended into a short free tube. Ornamentation consisting of unequal ridges of growth, with intervening microscopic spiral striæ.

Obs. This is so variable a species that I have been able to distinguish no less than four, or perhaps five, well-marked varieties in a large collection of specimens which has lately passed through my hands, besides Mr. Henderson's specimens. The above description applies only to the latter, and would require to be somewhat extended to include the varieties. Another point to be determined is the relation this species bears to Spiroglyphus marginatus, M'Coy, as it frequently forms a distinct groove for itself on the organism to which it is attached.

''Loc. and Horizon. In black bituminous shale at Katesmill, above Colinton, Water of Leith, associated with Anthracomya scotica'', R. Eth., Jun. In entomostracan shale, adhering to indeterminable bivalve shells at Woodhall, Water of Leith. Both horizons in the Wardie-Shale division of the Cement-stone group.

Serpulites, Macleay, 1839, Murchison's Silurian System, p. 700.

, M'Coy. Pl. I. fig. 3.

Serpulites carbonarius, M'Coy, Synop. Carb. Foss. Ireland, 1844, p. 170, t. 23. f. 32.

''Sp. char. Tube small, compressed, shelly, terminating posteriorly in two lengthened cylindrical tubes, the prolongation of the lateral thickened ridges (M'Coy'').

Obs. The posterior cylindrical tubes are not preserved; but the lateral thickened ridges are quite clear. Prof. M'Coy describes the tube as shelly; but I am satisfied that a certain amount of horny matter also entered into its composition. The longitudinal wrinkles on the surface of the tube are sufficiently fine to pass for striæ.

''Loc. and Horizon.'' In a bed of marine shale, below the ford at the