666 NEW YORK STATE MUSEUM 



passage out into a broad and deeper gulf extending to the north- 

 east continuously or discontinuously to beyond the coast of :he 

 maritime provinces. In this deepened head of the gulf the 

 Helderbergian fauna, traveling southward from a long sojourn 

 in inchoative condition in the region of the Gulf of St Lawrenee, 

 adding vitality and prolixity on its way (as shown at Dalhoujie 

 N. B.), sequestered itself in deepening water and was fruitfully 

 multiplied to its climax. The Helderberg fauna as a whole was 

 thus an invader from the northeast. The narrow bar which 

 separated its first assession from the Appalachian gulf was in 

 a state of degradation so extensive that, at the earliest period 

 of its presence, transgression over this barrier was readily 

 effected, but not a transgression which extended far, as the 

 barrier remained an obstacle to free migration. 



The Helderbergian, however, did not gain possession of an 

 extensive area in New York during its earliest manifestations, 

 its species commingled in some measure with the frail Siluric 

 congeries on the ground of central and western New York 

 which had endeavored to reinstate itself with the gradual fresh- 

 ening of the Salina sea, but in later stages of its existence the 

 reintegration of the barrier shut out from the area of the Appal- 

 achian gulf all evidence of its final phases (Becraft, Kingston 

 (=Port Ewen) beds). The area of the Helderberg in New York 

 was its fruitful center of dispersion, and thence its travels were 

 southward along the barrier, probably around its southern 

 termination, and from there into the Appalachian gulf in the 

 region of western Tennessee, Illinois and Indian Territory. 



Oriskany fauna 

 From the same direction and along the same thoroughfare 

 came the Oriskany, its center of variation and dispersion un- 

 questionably being in the region of Gaspe" bay, where now its 

 species are dispersed through 800 feet of limestone. Leaving 

 behind it species which may have survived in the Gaspe" 

 sandstones to a later period of Devonic time, it followed in the 

 train of the Helderberg fauna, manifesting itself most perfectly 

 in the silicious limestones of Columbia and Ulster counties. 



