518 Revieics — McHenry and Watts — Rochs and Fossils. 



In the present work the authors include under the general heading 

 of "Foliated Crystalline Rocks," granites that in places graduate 

 into gneisses, various schists, micaceous limestones, and grits, all 

 more or less sheared and foliated. Some of the quartz-schists are 

 very like that group known in the Scottish Highlands as " moyne- 

 schist " ; but the only area referred to as Archsean is that of Pettigo, 

 in Donegal, where the hornblendic and granulitic gneisses are 

 grouped with the " old gneiss " of the north-west Highlands. 

 While some of the gneisses are foliated granites, others appear to 

 be altered grits ; and with regard to age, the fact is that the 

 complex masses of older plutonic and metamorphic rocks have 

 not yet been fully investigated. Limestones yielding forms referred 

 with some doubt to Corals, occur interbedded with the quartzites and 

 schists in Donegal ; and certain shales at Fintown, in Ulster, which 

 occur in association with foliated rocks, have yielded markings like 

 Graptolites. Hence it is as yet impossible to say what infoldings 

 of altered sedimentary and fossiliferous strata may occur amid older 

 and perhaps pi-e-Cambrian crystalline schists. 



No traces of the old trilobite-faunas of the Cambrian rocks have 

 yet been discovered. These rocks in Ireland have only yielded 

 few and doubtful fossils ; but the problematical forms named 

 OldJiamia are regarded as of " probably organic origin." 



In the Silurian rocks the task of following out the zones indicated 

 by Graptolites, has borne good fruit, and the results at present 

 attained by the Geological Survey are duly indicated. Palfeon- 

 tological evidence has thus been obtained to enable more definite 

 correlations to be made with the English and Welsh divisions of 

 the Silurian system. 



The Dingle Beds and Glengarrifi" grits are grouped with the 

 Lower division of the Old Red Sandstone, and this is conformable to 

 the Upper Silurian ; while the Upper Old Red Sandstone (Yellow 

 Sandstone Series) passes up conformably into the Carboniferous rocks. 

 In ascertaining what has been done with regard to the Lower 

 Carboniferous rocks, and their relationship with the Upper Devonian, 

 we should have been glad of the names of some of the common and 

 characteristic species. As it is, genera only are mentioned, and the 

 vexed subject of correlation is not discussed. 



Of the newer formations but little need here be said ; it is 

 interesting, however, to note that the " Manure Gravels" of Wexford 

 are considered to be of Pliocene date, though newer than the St. 

 Erth Beds. 



The Igneous rocks are arranged so as to give the student a history 

 of volcanic action in Ireland from the earliest times to the great 

 eruptions of Tertiary date. Particular accounts are given of the 

 contemporaneous or interbedded volcanic rocks that lie amid the 

 Foliated Crystalline rocks, the Lower and Upper Silurian, the Old 

 Red Sandstone, Carboniferous, and Lower Tertiary ; and of the 

 intrusive rocks which penetrate all formations up to the Lower 

 Tertiary. A great many eruptive rocks have for the first time been 

 examined in detail and described, while some of them have proved 



