EURYPTERUS SHALES OF THE SHAWANGUNK MOUNTAINS 3O3 



in shallow water. Our present knowledge of the habits of the 

 merostome crustaceans derived both from the living and fossil forms, 

 indicates the shallow water or barachois origin of all sediments in 

 which these remains abound. In the Shawangunk section we have 

 a fauna constantly repeating itself through a thickness of 650 feet 

 which elsewhere appears only and briefly at the base of the Salina 

 series. 



While it may seem hazardous to infer that this section repre- 

 sents onty the early part of the Salina stage, yet the section of 

 these rocks afforded by the Nearpass quarry at Port Jervis shows 

 that above the Shawangunk grit are the red Longwood shale, 

 Poxino Island shale, Bossardville limestone and the Decker Ferry 

 limestone. All these are below the layer now correlated with the 

 Cobleskill horizon of central and western New York. At Poxino 

 island, Dr Kiimmel estimates the thickness of the red shale at 

 2305 feet. We have then in southeastern New York and northern 

 New Jersey a very great thickness of deposits which now seem to 

 be the equivalent of the Salina shales and dolomites of central and 

 western New York and though in the latter region it has been 

 found practicable to subdivide the Salina deposits into a series of 

 minor stratigraphic units, the total thickness of them all is very 

 much less than one half, probably considerably less than one third 

 of the thickness of the deposits which we may ascribe to the same 

 stratigraphic interval in the region under discussion. 



The continuity of this crustacean fauna indicates iminterrupted 

 communication through the secluded waters of this period. Were it 

 not for the presence of the fauna at the east one might entertain the 

 conception of a torrential origin for the heavy mantle of Shawan- 

 gunk grit. This might be in entire harmony with the prevalent arid 

 condition of the time, but the innumerable repetitions of this fauna 

 preclude this idea. This arenaceous deposit, we have noted, belongs 

 to a portion of the gulf set off from that further west by the pro- 

 trusion of the Helderberg shoal or peninsula, an eastern bay receiv- 

 ing a rapid terrestrial drainage with resultant deltiform deposition 

 of low gradient, from an elevated but distant source. The intru- 

 sion of these terrestrial waters at the east prevented highly saline 

 conditions. 



Description of the fauna 



In attempting to portray the character of this interesting asso- 

 ciation of merostomes I am obliged to recur to the statements 

 already made in regard to the preservation of the bodies. Cir- 



