134 Correspondence — Rev. J. F. Blake. 



ample time for the formation in mountain regions of deep valleys, 

 down which, during the Glacial epoch, glaciers would take their 

 course. He noticed the evidence of this local glaciation furnished 

 by the striation of the Welsh mountains, from which he inferred 

 that these mountains as a whole were not overridden by a great 

 ice-sheet coming from the north, and he described the course of the 

 glaciers flowing from the north-west slopes of Snowdonia as being 

 in the directions west, north-west, and north. These glaciers, 

 however, did not reach the region now occupied by the Menai Straits, 

 but spread out in broad fans on the north-western slopes of the hills 

 now overlooking the Straits, a fact indicated by the directions of 

 the glacial strias in these parts. Anglesey, therefore, was not 

 glaciated by ice-masses coming from Snowdonia ; and as the stria- 

 tions on that island point directly towards the mountains of Cum- 

 berland, the author inferred that these markings were produced by 

 a great ice-flow coming from that region, reinforced probably by 

 ice-streams from the north of Scotland, and which were large and 

 powerful enough to prevent the glaciers of Llanberis and Nant- 

 ffrancon from encroaching on the territory of Anglesey. 



The author described the rocks bordering the Straits as consisting 

 of nearly horizontal Carboniferous strata, which, from appearances, 

 must once have filled the whole of the region now occupied by the 

 straits. He considered that the softer shaly, sandy, and marly beds, 

 remains of some of which are still to be seen on the coast, were 

 swept away by the action of the great glacier coming from the 

 north-east, forming a valley now occupied by the sea ; and in sup- 

 port of this view he cited the valley of Malldraeth Marsh, running 

 across Anglesey, parallel to that of the Menai Straits, about 4 miles 

 to the north-west, which a very slight change in conditions would 

 convert into a fjord, differing from the Straits only in being closed 

 at the north-east end. 



ooie,i^:Es:po2sriD:Ei<TGE- 



[^TJie subjoined letters, from the Eev. J. F. Blake and Prof. G. A. 

 Lebour, were, hy an oversight, omitted to he published in last month's 

 Magazine ; the Editor begs to apologise for the unintentional delay 

 which has occurred.^ 



LOWEE SILURIAN FORAMINIFEEA. 



Sir, — In some thin-bedded, finely -laminated shales, referred by 

 the Geological Survey to the Caradoc series, at a spot about eight 

 miles east of Aberystw^ith, in the neighbourhood of the lead-mines, 

 I noticed a slab covered by numerous hollows, coloured red as if from 

 oxide of iron, and of an elongated shape. On examining these 

 hollows more carefully with the microscope, several of them present 

 most perfect outlines of Bentalian Foraminifera, and two in particu- 

 lar present that peculiar tubular elongation for the main foramen, 

 which is denoted by the term Ectosalenian. The walls between the 

 chambers are also indicated in several, though obscurely, the sub- 



