CAMBRO-ORDOVICIAN LIMESTONES 703 



basal member forms a high elbow ridge, which is faulted off on the 

 west side. 



A wedge-shaped inlier of Conococheague is brought to the surface 

 by an anticline in the vicinity of Welsh Run, in the Mercersburg 

 quadrangle, where the rocks are similar to those in the Chambersburg 

 area, but the siUceous banding is less pronounced. In the Carhsle 

 quadrangle neither the basal siliceous beds nor the sandy laminated 

 beds at the top are prominently developed. 



Few fossils have been found in this formation, and such as have 

 been collected are poorly preserved and difficult of determination. At 

 the base a few good specimens of trilobites and brachiopods were 

 obtained in the western portion of Scotland, and fragments of the 

 same were seen in the basal conglomerate. These comprise Dikelo- 

 cephalus hartii Walcott; D. sp. undet.; and Billingsella like B. des- 

 mopleura. The trilobites place this part of the formation definitely 

 in the Saratogan (Upper Cambrian). In the basal conglomeratic 

 beds a species of Cryptozoan, probably C. proliferum Hall, charac- 

 terized by a mammiferous surface, the elevations J to i inch in diame- 

 ter, is rather generally present. In cross section the fossil appears to 

 consist of thin closely folded laminae, and is illustrated in the writer's 

 former paper.' 



These siliceous banded limestones, together with overlying finely 

 laminated purer rocks, were previously described by the writer under 

 the name Knox limestone. The differentiation of the upper rocks as 

 a separate formation, next to be described, necessitates the giving of 

 a new name to these lower beds, and Conococheague, the name of 

 the large stream on the banks of which, in the town of Scotland, 

 the best exposures occur, has been selected. The Conococheague 

 and the overlying Beekmantown, therefore, comprise the Knox group. 



BEEKMANTOWN LIMESTONE 



The Beekmantown is a rather pure limestone lying between the 

 siliceous Conococheague below and the very pure Stones River above. 

 A minutely laminated appearance on weathered surfaces of many of 

 the beds, due to their impurities, and pink to white fine-grained 

 limestone or]marble are characteristic features of the formation. Near 



I Loc. cit. p. 217. 



