ATLANTIC REGION 577 



found in the Lower Lykholm beds of Esthonia, which, according to Bass- 

 ler, correlate with our Lower Trenton. Stropliomena expansa occurs even 

 higher than this, being found in Esthonia in the Borkholm limestone, 

 which is regarded as late Ordovicic. Maclurea (Maclurites) logani Salter 

 is found in North America in the Black Eiver beds of Allumette Island, 

 Ottawa Eiver (Leroy horizon) and the Mingan Islands, Canada, and also 

 in Bessels Bay, Arctic America. It appears thus to belong to the fauna 

 entering North America from the Atlantic. Tetradium peachi Nich. and 

 Eth. is now referred to Solenopora compacta (Billings), a form widely 

 distributed in the Middle and Upper Ordovicic, especially in the Black 

 Rivei* and Trenton of eastern North America. Nidulites favvs (Salter), 

 which also occurs in this limestone, has been obtained from similar beds 

 in Quebec. The graptolites of formation 6 are mostly typical of the 

 American Normanskill fauna, all but number 4 having been recorded 

 from this country. 



According to this standard, then, our Normanskill fauna should lie 

 above the Black River fauna and represent essentially early Trenton — a 

 conclusion reached likewise by Euedemann. 



The Benan conglomerate (7) rests disconformably on the Stinchar 

 group, cutting across the graptolite shales on which it rests at Benan 

 Burn, until at Auchlewan Burn it rests on the eroded surface of the 

 Stinchar limestone (No. 5). This descent across the graptolite shales 

 occurs within a distance of 200 yards. The conglomerate in places is 

 almost destitute of bedding planes, except by the arrangement of pebbles 

 into lines in some cases. It furthermore contains fragments of the lime- 

 stone. 



The matrix of the conglomerate is derived from the disintegration of 

 the basic igneous rocks of the region. The pebbles, often of the size of 

 boulders and generally well rounded, are derived from the Arc-nig vol- 

 canic plateau. The disconformity does not necessarily mark a hiatus of 

 great extent, since the conglomerate is a continental deposit which was 

 spread out over the marine series, the terrestrial sediments pushing back 

 the seashore as they advanced. This conglomerate marks the inpouring 

 of a mass of coarse river sediment at this place from the highland lying 

 to the northwest, which had been elevated, and it corresponds essentially 

 to the conglomeratic deposits built into the retreating Ordovicic sea in 

 North America, but derived from the Appalachian land on the southeast. 

 The formation of the American representative, however, the Bald Eagle 

 conglomerate, began somewhat later than the Benan, which is regarded 

 as closing the Llandeilan stage, while the Bald Eagle is post-Trenton. 

 That the region was again submerged in Caradocian time is shown by 



