EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 97 



The Gasps Geosyncline 



The foregoing details of the apparent geological structure of Gasp^ 

 are supplemented in the following pages and plates by the immutable facts 

 on which must be based all inferences relating to the faunal problems. The 

 latter will be subsequently considered. Apart from these, however, we 

 may here briefly contemplate the significance of the great crustal depression 

 in whose sediments these faunas are found. 



A geosyncline is not properly conceived as a depression bounding an 

 existing or an ancient continental mass but isostatic equilibrium requires 

 that if there is a continental surface at one side of such great depression 

 there will have been a similarly stable continental area at the other. This 

 view has been forcibly expressed by Haug' as the essential condition of 

 such depressions. Therefore in view of this conception we predicate with 

 confidence a continental area outside and eastward of the great Appa- 

 lachian depression, during all the period of deposit of the sediments now 

 filling it. Appalachian land now reduced to a region of coastal folds, rep- 

 resenting the deposits made in this geosyncline is left standing at the 

 margin of the continental mass by the invasion of the sea over all but the 

 merest remnant of the more ancient land area at the east. We are not 

 likely too strongly to emphasize the fact that a geosyncline, though a line 

 of weakness and mobility of the crust, is in its essence a seaway, a channel 



have found, lying with fossiliferous boulders of Gaspe sandstone, a block of gray and pure 

 crinoidal limestone profusely filled with specimens of a large Productus. The species has 

 a finely ribbed surface, spineless except for suggestions along the hinge, thick shell with 

 deep muscle scars, heavy cardinal process; features which characterize the Productus 

 comoides Sowerby of the European Coal Measures, but I do not find that it possesses 

 the broad hinge areas and ventral teeth which led Waagen to place this species in his 

 genus Daviesiella. It is like P. cor a d'Orbigny but a heavier shell. At all events it is a 

 Coal Measure fossil. Whence this specimen came I would not venture to say. No evi- 

 dence of such rock beds exists in the country but the past 250 years have brought ballast 

 to these shores from many ports, from France and England, Portugal and the Brazils, 

 which may well have furnished such a block. 

 'Soc. Geol. de France. Bui. 1900, 28, 632. 



