R. Etheridge, jun.—Carboniferous Tubicolar Annelida. 261 
dextral, convex on one side, flattened, or irregularly piled on the 
other, and almost similarly marked. It may, however, be said 
generally, that the coiled portion of S. pusillus is wound much more 
closely than 8. helicteres, the volutions less in the same plane with 
one another, and the termination of the last whorl, where it quits the 
coiled portion of the tube, directed more to one side than in Salter’s 
species. In mass, the peculiarities of S. helicteres become very 
marked, especially the compressed tortuous tube with from four to 
six turns, or open volutions. I have examined authenticated 
examples of Serpula subannulata, Portlock,' from Co. Derry, in the 
Museum of Practical Geology, and I believe this species to be only 
a large condition of Spirorbis or Serpula helicteres, Salter, in which 
case Portlock’s name will have to be adopted. 
The internal structure of Sp. helicteres has been studied by Mr. J. 
Young, who states that the tubes are traversed by thin, concave, and 
imperforate, transverse septa, placed at irregular distances, and so 
coinciding with the structure of certain recent Serpule in the 
Hunterian Museum.’ In fragments of the free tube from Liddesdale, 
sent to me by Mr. Bennie, these divisions are sometimes to be seen, 
and the tube appears to possess a peculiar facility for breaking across 
into small pieces at these diaphragms. 
Loc. and Horizon.—Shore, near Fifeness, to the N.W. of the 
Balcomie Sands, Fife (Rev. T. Brown); Clubbiedean Reservoir, N. 
end of the Pentland Hills (J. W. Salter, Geol. Survey Scot.) ;% 
Nether Tarisch, on the Ayr Water, E. of Sorn (A. Macconochie, 
Geol. Survey Scot.) ; Ayrshire coast, between the Heads of Ayr and 
the “ Deil’s Dyke” (J. Young) *; these localities are all in the 
Cement Stone Group of the L. Carboniferous series of Scotland; it 
is, however, stated by Mr. Young that S. helicteres occurs in a thin 
mussel- band ironstone of the Coal-measures at Newton Cambuslang.° 
4,—Spirorbis caperatus, M‘Coy. (Plate VII. Figs. 16-18.) 
Spirorbis caperatus, M‘Coy, Bynop. Carb. Lime. Foss. Ireland, 1844, p. 169, t. 238, 
ae 
Mortis, Cat. Brit. Foss. 1854, 2nd ed. p. 1 (without description). 
Etheridge, jun., Mem. Geol. Survey Scot. Expl. 23, 18738, p. 98. 
Armstrong and Young, W. Scot. Foss. 1876, p. 43 (without 
deser iption). 
Serpula et Spirorbis caperatus, Bigsby, Thes. Dey.-Carbonif. 1878, p. 243 (ébid.). 
Sp. char.—Tube discoid forming a closed helix of two whorls, and 
then becoming extended into a produced and somewhat curved free 
portion ; section round; surface occupied by equidistant, sharp and 
prominent, transverse ridges. Usually attached to the surface of 
shells, etc. 
Obs.—This species was described by Prof. M‘Ooy from a single 
specimen, so that we must not expect his figure to present all the 
characters of the form as presented by a number of specimens. I 
1 Geol. Report, Londonderry, p. 363. 
2 Proc. Nat. Hist. Soc. Glasgow, ill. p. 329. 
3 Mem. Geol. Survey Scot. No. 32. p. 145. 
* loc. cit. p. 328. Soe. cit.) Tupi LOZ: 
