24 * EXPLANATION OF THE PLATES. 
slate being of a ferruginous or yellow ochre colour ; they are accompanied, 
at the same locality, by numerous and perfect examples of what appears 
to the author identical with Graptolithus flaccidus, Hall. Collected by 
the Geol. Surv. of Ireland, from cliffs, on the River Suir, a little north- 
west of the city of Waterford. See Paleontological Remarks, in Ex- 
planation of Sheets 167, &e., p. 25, &e., Geol. Surv. of Ireland. 
b. Original. Portion of one of these Graptolites, enlarged; showing central axis, 
and closely arranged double series of cellules. 
e-f. From original figures by the author, in Journ. Geol, Soc., of Dublin, vol. 
ix., pl. iv., figs. 2 a, 6, ec, and 3 b. 
e. Smallexample, with fine central axis projecting beyond the cell serratures 
at both ends. 
d. A very young specimen, upon which no serratures are visible, the outline 
being smooth, and the central axis projecting. 
e and f are considered to belong to the same species, and to be pressed in an 
opposite direction to 3 a, and 3 ec, a specimen from the same locality. 
Graptolites presenting this appearance were formerly described as distinct 
species, under the names of sealaris and scalariformis. Fig 8 e, in addition 
to the edge view, shows the axis prolonged at the upper part, above the 
compressed cells, to a considerable length; gradually swelling out in the 
centre, and provided with what appears to be a thread-like canal passing 
through it, and terminating in a small pointed filament. 
jf. An example of a similar variety to the previously described one, in which 
the mass of compressed cells beara much greater proportion to the axis, 
which is but slightly prolonged beyond them; e, d, e, and f, are all from 
the same locality, on the north-west flank of the Slieve Bernagh Moun- 
tains, at Belvoir, between Sixmile Bridge and Broadford, in the county 
Clare, and were collected by the Geol. Surv. of Ireland, from black slates 
in which this species and variety are very abundant, accompanied by 
Graptolithus ? gracilis, Hall, and a few other Graptolites. Vide Explana- 
tion to Sheet 133 of the Maps, Geol. Surv., Ireland. Pal. Notes by the 
author, p. 10, &e. 
This species, the most abundant and characteristic of all the Graptolites 
of the Silurian rocks, especially marks the Lower Silurian division; no 
double Graptolite having hitherto occurred above the Caradoc or Bala, 
LLANDEILO.—Shropshire; North Wales ; Dumfries. Catalogue of Brit. Foss., 
by Prof. Morris, second edition, 1854, p. 53. 
Lower LLANDEILO.—Tai-hirion ; Arenig, west of Bala, North Wales ; west 
of Stiper stones, Shropshire ; and Upper Luanpei10, South Wales; Mr. 
Salter, in Mem. Geol. Surv., vol., iii., p. 256. 
Carapoc or Bata Rocxs.—In Bala schists in many parts of Wales; also in 
earthy beds, ascribed to this formation, at Church Stretton, Shropshire ; 
Siluria, third edition, p. 73. 
Localities in Ireland.—Black slates, ? Llandeilo Ballymoney, and Ballinatray 
Bridge, Courtown Demesne, near Gorey, and Tinnaglogh, Ballyhack, Co. 
Wexford; Belvoir, Co. Clare ; Commons of Slane; Newtown Fortescue, 
Broomfield, and Cooksgrove, near Duleek, Co. Meath; also Balbriggan, 
Portraine, and Lambay Island, Co. Dublin; collected and determined by 
the author ; also Lisbellaw, Fermanagh; and Desertcreat, Tyrone ; speci- 
mens in the Portlock Collection, Mus. Geol. Surv. of Ireland. 
Fig. 4.—a-d. DIPLOGRAPSUS TERETIUSCULUS, Hisinger, sp. 
Prionotus, Hisinger, Leth. Suec., pl. xxxviil., fig. 4. 
