Notices of Memoirs — A. Somermil — Lizard Did rict. 565 



Extensive Unconformity. 



There is a perfectly unbroken downward succession as far as the 

 conglomerate at the base of (3) ; and, therefore, as (4c) is admitted 

 on all hands to be of Triassic age, the remainder of (4) and the 

 whole of (3) must be of Triassic age also; (3) lies indifferently 

 upon either member of (2) or upon the upper part of (1) ; it is 

 therefore slightly unconformable to the beds below. These are 

 admitted on all hands to be Permian; therefore the break between 

 the Trias and the Permian is at the base of (3). The author con- 

 siders that the whole of these rocks form the natural basement beds 

 of the Neozoic rocks, and that the dividing line between the Palaso- 

 zoic rocks and the Neozoic age should be taken somewhere between 

 the Red Rocks of the Salopian type (to which he would restrict the 

 term Permian) and the true New Red, as the term is here employed. 

 He considers that the New Red proper bears the same relation to 

 the Jurassic and Rhsetic Rocks that the Upper Old Red Sandstone 

 does to the Carboniferous, and that the Salopian Permian may 

 possibly occupy the same relation in regard to the Carboniferous 

 rocks as the Glengariff Grits do to the Silurians. Some at least of 

 the Salopian rocks may be simply Carboniferous rocks stained by 

 infiltration from the New Red. 



The author regards the St. Bees Sandstone as mainly equivalent 

 to the Bunter, and proposes that the term Bunter Marls should be 

 applied to the marls which here (and in Devonshire, etc.) occur at 

 the base of that subdivision. 



II. — The Igneous Rocks op the Neighbourhood of Builth.^ By 

 Henry Woods, B.A., F.G.S. 



AN account of the geology of the Builth district was given by 

 Murchison in the ''Silurian System" (1839), since which 

 scarcely anything has been written on it. A series of igneous rocks, 

 associated with beds of Ordovician age, stretches from near the town 

 of Builth to beyond Llandrindod. In this paper the author confined 

 himself to the southern half of this area, giving a preliminary 

 description of the distribution and characters of the rocks met with, 

 namely, diabase, rhyolite, porphyrite, andesite, and ashes. 



HI. — On the Relations of the Rocks of the Lizard District.^ 



By Alex. Somervail. 

 ri^HESE rocks include the hornblende-schist, serpentine, gabbro, 

 J_ granite, etc., which the author regards as all belonging to the 

 same period of geological time, and to have segregated or separated 

 out from each other during the cooling of a homogeneous magma. 



There seems absolute evidence in the field to show that the 

 serpentine is a non-intrusive rock, that it was the first portion of 

 the magma to cool, and is broken through by all the other rocks, 

 but that it is intrusive into none. 



The relations between the serpentine and the diorite and portions 

 1 Abstracts of Papers Eead before the British Association, Edinburgh, Aug-. 1892. 



