451 
Distribution of the Rhabdophora. 
Girvan Rocks. —The Girvan district, whence Salter pro¬ 
cured the few Caradoc Graptolites enumerated upon his lists, 
has also been partially worked out by myself. The general 
succession will be given in the sequel. Its strata, instead of 
being wholly of Caradoc age, have been found to include 
representatives of the Lower and Upper Caradoc, the Lower 
and Upper Llandovery, and the Tarannon. The asserted 
intermingling, in this area, of species elsewhere peculiar to 
distinct formations has also been ascertained to be purely 
mythical. Its Graptolites, which are those of the Moffat and 
Gala groups, correspond precisely in their vertical range with 
the same species in the eastern districts. 
The Coniston Mudstones. —The mistaken views of the 
geological age of the graptolitiferous beds of Westmoreland 
known as the Coniston Mudstones, or Skellgill shales, were long 
almost equally effective with those already noticed in delaying 
a true estimate of the vertical range of the British Rhalxlo- 
phora. By Professors Harkness and Nicholson* * * § , as tve have 
seen, they were at first unhesitatingly assigned to the Bala 
formation. Professor Sedgwick placed them sometimes in 
the Balaf, sometimes at the base of the true Silurian. Pro¬ 
fessor Hughes and Mr. Aveline J, who have most fully inves¬ 
tigated their physical relations, parallel them with the Taran¬ 
non shales of North Wales. By myself they have long been 
regarded as of Lower Llandovery age—a view first published 
by Dr. Nicholson § and myself in 1875, and subsequently 
adopted by Professor Harkness || and Dr. H. Hicks 1j. Mr. 
Marr, the latest student of these beds, agrees with the 
officers of the Survey in referring them to the Upper Mayhill**. 
Their Llandovery-Mayhill age may thus be now regarded as 
practically settled. 
Arenig and Llandeilo. —The Arenig and Llandeilo rocks 
of the neighbourhood of St. David’s were carefully studied by 
* On page 248, by an unaccountable oversight, Professor Harkness and 
Sir R. Murchison are together credited with the honour of having origi¬ 
nally worked out the general distribution of the fossils in the Lower 
Palaeozoic rocks of the north of England. It is almost needless to 
point out that the latter name should be that of Professor II. A. Nichol¬ 
son, whose many accurate and beautiful memoirs upon this subject have 
(especially for the graptolithologist) made the Lake district classic 
ground. 
t 1 Palaeozoic Rocks and Fossils,’ Introduction, p. xxi; and Quart. 
Journ. Geol. Soc. vol. i. p. 442. 
X Geol. Surv. England and Wales, Explan. Sheet 98 N.E. p. 3, See. 
§ Report British Association, 1875. 
|| Quart. Journ. Geol. Soc. vol. xxxiii. p. 478. 
Geological Magazine, 1876, p. 336, &c. 
** Quart. Journ. Geol. Soc. vol. xxxiv. p. 879. 
