154 
SILURIA. 
[Chap. VIII. 
of Lauderdale, and of Annelide -tracks both at Siccar Point and at several 
parts of the valley of the Dye Water. His memoirs contain the most de- 
tailed account which has yet been given of any part of the Silurian region 
of the South of Scotland, and may be referred to as illustrating the con- 
tortions, foldings, metamorphism, and intrusive rocks of the Silurian series 
in this part of the kingdom. 
A third traverse of the South- Scottish Hills, made along the line of the 
Caledonian Eailroad*, exhibits the same general features, and many of the 
same details, as the preceding parallel sections. The Dumfries axis of the 
older and unfossiliferous greywacke, as before stated, throws off anthracitic 
and graptolitic schists southward to Lockerby, and to Moffat on the north. 
The details of these must be sought for in the memoirs of Professor Hark- 
ness, who has shown to what a great extent some of the schists are charged 
with Graptolites. Among them may be cited the wide-spread forms of 
the Llandeilo flags — Diplograpsus pristis, D. folium, D. teretiusculus, and 
Graptolithus Sagittarius, all found in the older rocks of Sweden, also Grap- 
lithus lobiferus, a Bohemian fossil, with other species found in Lower 
Silurian strata elsewhere in the British Isles, or peculiar to these deposits. 
Twenty-five species have already been enumerated from this district 
alone f. (See Poss. 12. p. 61.) 
All these rocks, anthracitic and aluminiferous, which are charged with 
Graptolites and Annelides, dip northwards from Moffat to Abington, and 
thus pass under other masses visible in this direction. The latter, which 
occupy the tracts of the Lead Hills and other lofty summits, are metallife- 
rous schists, in parts much altered, and penetrated by felspar-porphyries 
with other igneous rocks. They were celebrated for yielding gold-ore in 
the reigns of the Pourth and the Pifth James of Scotland. Associated 
with, or rather overlying them, is a rude breccia, partly calcareous, which 
may possibly represent the Wrae limestone of the diagram at p. 150. But 
further northward other and still thicker strata of Silurian age are visible, 
which are overlain by the Old Bed Sandstone and coal-fields of Lanark- 
shire. Though satisfactory in exhibiting a good ascending succession from 
the base of the sedimentary series, I consider this section less perfect, in 
carrying out the order to beds on or above the horizon of the Llandeilo 
limestone, than that which is figured above (p. 150). 
The fourth, or west-coast traverse, from Luce Bay across "Wigtonshire 
and part of Ayr, does not develope the order of the lowest masses, but adds 
much to our acquaintance with the more fossiliferous strata of the 
system, by exhibiting beds more copiously charged with fossils than any 
other Silurian rocks in Scotland $. 
* Prof. Nicol and myself examined this section 
together in 1850. See Quart. Journ. Geol. Soc. 
vol. vii. p. 137. 
t See Harkness, Quart. Journ. Geol. Soc. 
vol. vii. p. 48 ; and M'Coy, Palaeozoic Fossils of 
the Cambridge Museum. 
J Accompanied by Professor Nicol, I examined 
this tract in 1850. Our fossil-collector was the 
late Alexander M'Callum, of Girvan, who searched 
every locality with great assiduity. See details in 
my Memoir on the Silurian Kocks of the South of 
Scotland, Quart. Journ. Geol. Soc. vol. vii. p. 137. 
