REVIEW OF OLD AND NEW STANDARDS OF PLEISTOCENE DIVISION 435 



marine sands, both erratically intercalated in the clay at the base of the 

 "lower Boulder-clay" of the coast of Holderness. Yorkshire. These 

 erratic blocks contain a fauna more arctic than that of any other English 

 Quaternary deposit ; of 100 species, 87 are related to modern arctic types- 

 There are deposits of the same age in Ayrshire, on the east coast of the 

 North Sea, and on the German-Baltic coast, Yoldia arctica and A start a 

 borealis being characteristic arctic species. 



Final phase. The terminal phase is one of continental depression and 

 marine elevation (deep-water clays with Yoldia myalls and Y. arctica). 

 Following the deposits of the Yoldia my alls beds, there was a marked 

 marine recession and continental elevation, the shorelines lowering- 

 themselves to the present level on the coast of Yorkshire, of Scotland and 

 Ireland. Thus a very low shoreline .preceded the maximum glacial ex- 

 tension on the British Isles (II Saxonian-Mindelian). The marine 

 fauna of these beds resembled closely the modern British fauna. At 

 Sewerby, above the marine shore, are deposits of continental rivers con- 

 taining a warm fauna little different from that of the Forest Bed 

 (Elephas antiquus, Rhinoceros merckii, Hippopotamus amphibius, Hyama 

 crocuta), but lacking [Osborn] the cold mammal fauna of the Forest 

 Bed {Elephas primigenius, Ovibos moschatus, etcetera). 



[= II Glaciation, Saxonian of Geikie] 



Milazzian Stage of Deperet. — The great Scandinavian glacier (II 

 Mindeiian-Saxoniaii) now covered the British Tsles, except the region 

 south of the Thames and the Bristol Channel. It deposited the "lower 

 Boulder-clay," locally known as Ked, Basement-clay, and Chalky Boulder- 

 clay; the "lower Till" of Scotland; in the Boulder-clay, especially near 

 the coast, are arctic species of marine shells, probably brought with 

 floating ice as erratics, but there are no contemporaneous marine deposits. 



[= Second Interglacial Stage, Tyrolian of Geikie, post-Saxonian] 



The climate warmed and the great Saxonian glacier retired. To this 

 phase belong the sands and gravels of variable thickness, intercalated 

 between the "lower Boulder-clay" and the "upper Boulder-clay," and con- 

 taining marine shells, arctic and British. These shell deposits, formerly 

 regarded (Geikie, 1914.1) as proofs of submergence of the British Isles 

 to a depth of nearly 500 meters, have more recently been shown to be 

 displaced fossils contained in morainal detritus and erosion, since they 

 include certain Pliocene mollusks evidently derived from Pliocene rocks. 



