PALEOZOIC TIME — LOWER SILURIAN. 



517 



720. 



The fossils discovered by A. Wing in the Taconic formation in the limestone of cen- 

 tral Vermont were from many localities, and were more or less perfectly determined by 

 Billings of Canada (Am. Jour. Sc, xiii., 1877). Some of them are Pleurotomaria stami- 

 nea, Pleurocystites tenuiradiatus, Crinoidal disks, and large specimens of 3Iaclurea from 

 West Rutland ; Trinucleus concentricus from Hubbardton ; from East Cornwall, Ste- 

 nopora fibrosa, S. Petropolitana, with species of Orthis, 

 Strophomena, Bhynchonella, and Orthoceras, pronounced 

 Trenton by Billings ; north and south of East Cornwall, 

 Ehynchonella beds containing pygidia of Trilobites, a large 

 Maclurea, Bathyuriis Saffordi ; at Bascom's Ledge, 3 miles 

 west of south of West Cornwall, Asaphus catialis, Bathyu- 

 rus conicus, Maclurea matutina, made Calciferous by Bil- 

 lings ; east of Shoreham, Bathyurus extans, Columnaria 

 alveolata, Trinucleus concentricus; in southern Bridport, 

 Asaphus canalis, Bathyuri, Maclurea matutina ; in Orwell, 

 Petraia profunda (?), Stenopora fibrosa, and S. Petropo- 

 litana, Beceptaculites Neptuni ; at Ellsworth Ledge, 2 to 3 

 miles west of Middlebury, a large Orthoceras, Bathyurus 

 Saffordi, and from higher beds B. Angelini, Asaphus canalis, 

 Maclurea, Orthis, Leperditia, Crinoidal stems ; 2 miles 

 north of Middlebury, the slightly curved Oi'thoceras, here 

 figured, natural size, having 40 to 52 septa to an inch (1877); 

 and half a mile to the northwest a large Maclurea. For 

 an account of the discoveries of Dwight and others, see 

 the references already given, page 495. The discoveries 

 of Walcott were among the latest, and as they were 

 made in the typical quartzyte of Vermont almost down 

 to the Massachusetts line, also in the Eolian limestone 

 just west, in Bennington, Vt., Williamstown, Mass., and 



in eastern New York, and in other localities in western Vermont and eastern New York, 

 and thus covered all the Taconic formations, the demonstration became complete that 

 the Taconic series is simply a combination of the Cambrian and Lower Silurian. 



Orthoceras prlmigenium ? 



EUROPEAN. 



The Lower Silurian series of Great Britain comprises, commencing 

 below, the following groups : — 



1. The Arenig group (Sedgwick, 1852) : slates and flaggy sandstones 

 which rest comformably on the Tremadoc slates of the Upper Cambrian. 

 The beds occur in North and South Wales, and have a thickness of 2500 

 feet in the latter. The stiper stone beds of Shropshire are here included, 

 and the upper part of the Skiddaw slates. In Merionethshire, North Wales, 

 the volcanic rocks of this period include a lower series of ashes and con- 

 glomerates, in some places 3300 feet thick ; a middle group of felstones 

 and porphyries 1500 feet thick ; and an upper series of fragmental deposits 

 800 feet. 



2. The Llandeilo flags : sandstones and shales of Llandeilo in Caermar- 

 thenshire, Wales, where first described by Murchison (1834). — In West- 

 moreland and Cumberland, or the Lake District, the volcanic deposits of 

 this period, but beginning in the Arenig and continuing through the Bala, 



