QUATERNARY DEPOSITS OF BRITISH ISLES BROOKS. 335 



River, in the south of Inishowen, the whole section being here above 

 high-water mark. 



The peat bed between the gray sands is described by Mr. Lloyd 

 Praeger as "the first bed still extant showing the ushering in of 

 temperate conditions ; " it contains a flora of marsh plants, sedges, 

 flags, and rushes, with the fruit and branches of hazel, alder, oak, 

 willow, and Scotch fir. On the upper surface of the bowlder clay 

 and in the peat, remains of Cervus magaceros were found. At Bel- 

 fast it is 27 feet below high water and at Downpatrick, in the Quoyle 

 estuary, it is far below low water, but at Tillysburn, Holywood, 

 Jiallyholme, Carrickfergus, Glenarm, Ballintoy, and Portrush it 

 outcrops between tide marks. It is by no means certain, however, 

 that all the forest beds exposed on the shore are on the same 

 horizon as the Belfast bed ; some of them may be later. 



Above the second bed of gray sand occurs the lower estuarine clay, 

 or ScrobiculaA^ zone ; essentially a littoral clay, typically brownish 

 blue, somewhat sandy, containing abundant Zostera manna, and a 

 vast number of shells of a few species which live between tide marks. 

 The same bed occurs at several other places on the northeast coast of 

 Ulster. It is always found below tide level, and it indicates that 

 during its formation the land stood about 10 feet above its present 

 level, and was slowly subsiding. The climate does not appear to 

 have differed from that of to-day. 



In places, as at Larne, the lower estuarine clay is, overlain by the 

 gravels of the 25-foot raised beach, but at Belfast, and also at Mag- 

 heramorne and Downpatrick, the place of the latter is taken by the 

 upper estuarine clay, a very pure and unctuous light blue deposit, 

 probably black before exposure to the air. It contains a very rich 

 and well-preserved fauna, chiefly of shells from the laminarian and 

 coralline zones, and characterized by the bivalve Thraoia depressa, 

 whence the bed is termed the Thra.cia zone. A full list of the fauna, 

 with remarks on the distribution of species, is given by Mr. Lloyd 

 Praeger (1806). The shells are mostly of large size, and include 

 species which are not now known from the shores of Ulster. Rissoa 

 alha, very common in the clay, is only known as a recent species 

 from Bantry Bay, whereas R. parva, the present common form, is 

 rare in the clay. Jeffreysia opallna, practically unknown, living in 

 Irish waters, is common, and also large specimens of Odostomia 

 minima, now rare and dwarfed. As a whole the fauna, like that 

 of the raised beaches, indicates a rise of several degrees in the tem- 

 perature of the sea water, while the land must have stood somewhat 

 below its present level. 



After this period of depression, a slight elevation set in, resulting 

 at Belfast in the formation of 2 feet of yellow sand containing many 

 shells, including TKrwcla and ScribiculaHaj evidently washed out of 



