3820 Dr. C. Callaway—The Archean Controversy. 
therefore, may infer a general equivalence; but it cannot be proved 
that the process of schist-making was strictly contemporaneous in 
the two districts. It may however be safely asserted that the 
Malvernian rocks are Older Archean; for the principal types, 
granites and modified diorites, occur as derived fragments in the 
conglomerates of the Newer Archean of Shropshire. 
The Newer Archean, the Uriconian, is a volcanic group resembling 
the Pebidian of St. Davids, of which it is the probable equivalent. 
But recent discovery suggests that this well-known formation may 
have to be thrown back to a period more remote from the Cambrian 
than has commonly been supposed. 
The slates, grits, and conglomerates of the Longmynd have 
been usually regarded as the stratigraphical equivalent of the 
Llanberis and Harlech groups. For some years, I have doubted the 
accuracy of this determination. In 1878,1in announcing the dis- 
covery of Cambrian rocks at Caer Caradoc, I described a thin band 
of limestone in the Hollybush Sandstone at the north-eastern ex- 
tremity of the ridge. This limestone was fossiliferous, yielding, 
besides Kutorgina cingulata and Serpulites fistula, several species of 
indeterminable Brachiopoda and obscure fragments of a trilobitic 
nature. Subsequent visits brought to light better specimens, which 
convinced me that the fauna was of a very ancient facies; and I 
have been in the habit of provisionally referring it to the Menevian 
epoch. As there appeared to be a considerable break between the 
Hollybush Sandstone and the Longmynd series, it seemed hardly 
possible to retain the latter in the Cambrian. In this unsettled state 
of the question, I proposed” in 1887 to call this great group of rocks 
by the name of “ Longmyndian.” This term has been adopted * by 
Prof. Lapworth, and he has obtained most important evidence in 
favour of the Archean age of the strata. Mr. H. Keeping, of Cam- 
bridge, working under his direction, has collected from the limestone 
at Caer Caradoc material which enables Prof. Lapworth to “recog- 
nize a large and well-marked species of Olenellus,” as well as to 
make out the generic characters of more of the Brachiopoda, and he 
concludes that the Pre-Cambrian age of the Longmyndian is “a 
matter of fair probability.” Prof. Blake goes further, and correlates * 
the Longmyndian with his “Upper Monian” of Bray Head. To 
sum up, we find that the most recent discovery, so far from invali- 
dating my conclusions with reference to the occurrence of Archean 
rocks in Shropshire, renders it possible that a third system will be 
added to the list. We should thus be able to record the existence 
in the West Midland area of three magnificent rock-systems of 
Archean age, viz. 1. Malvernian (igneous and igneo-metamorphic), 
2. Uriconian (volcanic and sedimentary), 38. Longmyndian (sedimen- 
tary). Ihave not here discussed the Rushton Schists,°’ because their 
position is uncertain; but I have little doubt that they are Pre- 
Quart. Journ. Geol. Soc. 1878, p. 758. 
Trans. Shrop. Arch. Soc. 1887. 3 Grox. Mac. Nov. 1888, p. 484. 
Quart. Journ. Geol. Soc. 1888, p. 543. 
1 
4 
5 Described in this Magazine, Aug. 1884, p. 362. 
aS 
