Notices of Memoirs — Rev. W. Lower Carter — TJsk and Wye. 521 



genus Simhirskites, but these beds have of late years been so poorly 

 exposed that no further information can be given regarding the 

 distribution of these fornis. 



In the zone of Belemmtes briinsvicensis Ammonites only occur at 

 the extreme base, wliere there are a few examples of one of the 

 Sintbirskites, and in its uppermost beds, where the genus Hoplites, 

 represented by B. Deshayesi, reappears associated with forms of the 

 genus Oppelia, the whole of the intervening deposits being apparently 

 devoid of these fossils. 



In the beds with Belemnites bltoaldi, which may prove to be 

 a distinct zone between the brunsvicensis and minimus zones, no 

 Ammonites have as yet been detected, but in the minimus zone 

 M. inferruptus, Brug., has been found. 



The Criocerata liave been found to exist in most, if not all, the 

 deposits from the uppermost part of the Belemmtes lateralis zone to 

 the top of the Belemnites brunsvicensis zone, and are especially 

 numerous about the middle of the Belemnites jnculum zone. They 

 are, however, difficult to determine, being both fragmentary and 

 ill-preserved. 



The paper concludes with a list of the species of Crioceras, 

 including those described in " Argiles de Speeton " and those met 

 with by the author, and determined chiefly by Dr. A. von Koenen. 

 This short list might, doubtless, be greatly extended by anyone 

 conversant with the forms of this group. 



VI. — Notes on the Glaciation of the Usk and Wye Valleys. 

 By the Rev, W. Loweb Cakter, M.A. 



DURING a recent holiday the author was able to study the glacial 

 deposits of the district to the north of the South Wales Coalfield. 

 The gravelly deposits of Old Red Sandstone material which are 

 characteristic of the valley of the Usk between Brecon and 

 Abergavenny (see "Geological Survey Memoir") have been traced 

 for some distance to the north-east of Brecon and up the valley of the 

 Usk as far as Trecastle. Here the river breaks away from the old 

 * through ' valley, which is continuous to Llandovery and rises in the 

 Carmarthen Fans to the south. On the top of this red drift were 

 found large numbers of erratics of volcanic ash and breccia, which 

 the author supposes to have been derived from Ordovician outcrops 

 to the west or north-west of the area in question. These blocks, 

 •which run up to two tons or more in weight, are found all down the 

 Usk Valley below Trecastle, and over the col towards LLmdovery, 

 in the Gwyddrig Valley, as far down as ' Halfway.' The author 

 has traced them on the flanks of the Brecon Beacon as high as 

 Newadd (886 feet) and down to Talybont, where a large one was 

 found close to the canal tunnel (400 feet). At Llangorse they form 

 part of a moi-aiue which dams back the drainage to form Llangorse 

 Lake. They are found in large numbers at Talgarth, and were 



