•456 SCIENTIFIC RECORD FOR 1883. 



that contain, besides, Bilobites and Critziana, and are described *> a iden- 

 tical in character with the Arinoricau sandstone of Brittany. They are 

 followed by a great concordant series, in which the forms of Barrande's 

 second and third faunas are abundant. These strata, measuring in all 

 about GOO meters, with the basal saudstone, have near the middle the 

 roofing-slates of Luarca, which, like those of Angers in France, con- 

 tain the forms of the second (or Ordovician) faunas, while higher in the 

 series are slat* s and limestones with the third or true Silurian fauna. 

 Barrois applies the name of Silurian to the rocks of both the second 

 and third faunas, and includes therein, though not without hesitation, 

 the Scolithus sandstone, which he admits should, in accordance with 

 the views of British geologists, be included with the first fauna. The 

 Scolithus of these sandstones would seem to be similar to that of the 

 Potsdam of the Adirondack region (long since shown to be distinct 

 from that of the Primal sandstone of Rogers), and is described by Bar- 

 rois. as exhibiting an internal tube, and as resembling Yerticillopora, to 

 which he compares it. The Scolithus found at Port Henry on Lake 

 Champlain shows this internal tube. 



The American geologist is here reminded of the typical Potsdam 

 which rests on the crystalline rocks in the Adirondack region, while 

 near by, in Vermont and New York, are found the slates and lime- 

 stones of a still lower Cambrian horizon, the so-called Lower Pots- 

 dam, between which and the ancient crystalline rocks are interposed, 

 along the Appalachians, several thousand feet of quartzites, slates, 

 and limestones, constituting the Taconian, which may well be repre- 

 sented by the 3,000 meters of strata found by Barrois in Galicia be- 

 tween the primitive schists and the base of the fossiliferous Cambrian. 



The Devonian, which overlies conformably the Silurian in this part 

 of Spain, has a thickness of not less than 1,000 meters, and includes a 

 great amount of limestones and an abundant fauna. It is succeeded by 

 the carboniferous, having at its base a great limestone member, and 

 above, 2,000 or 3,000 meters of coal measures, with more than eighty coal 

 seams, many of them of value. The carboniferous limestone is in part 

 dolomitic, and is remarkable for its great deposits of ores of zinc, lead, 

 manganese, cobalt, and mercury, which are found in veins and fissures 

 in these rocks, and according to Sullivan and O'Reilly are post-Eocene 

 in age. 



TRIAS OF EASTERN NORTH AMERICA. 



Prof. George H. Cook has discussed the history of the Mesozoic areas 

 of eastern North America, constituting the new red sandstone, which 

 probably include both Jurassic and Triassic beds, and have already 

 been considered in the report of last year. Cook regards those from 

 South Carolina to Massachusetts, and probably also those of the Brit- 

 ish provinces, as having been at one time in some way connected, and 

 supposes that a great extent of these sediments thus defined was after 



