328 Annals of the Carnegie Museum. 



Twenhofel and Schuchert" have recently re-investigated the section 

 on the Mingan Islands, and find that all the strata, which are there 

 referable to the Chazy, are of Upper Chazy age. 



It seems then, that the Middle and Lower Chazy are developed 

 only within the limited area between Ticonderoga and the foot of 

 Lake Champlain, and that the view that this fauna entered the 

 continent along a channel which roughly corresponded to the St. 

 Lawrence trough is no longer tenable. The fauna could not have 

 come from the west, and with the St. Lawrence depression eliminated, 

 the only other directions are the south and east. The Chazy is 

 present in eastern Tennessee and Virginia, but is missing from the 

 intervening states of Maryland, Pennsylvania, New Jersey, and New 

 York as far as Ticonderoga. At the most southern exposures in 

 New York it is the Middle and not the Lower Chazy which rests upon 

 the pre-Chazy formation, so that the chances that the Chazy entered 

 from that direction are very small. It would seem that the only 

 chance for a connection with the Atlantic was from the East, directly 

 across the Green Mountains, and the sediments of that region are, 

 unfortunately, so metamorphosed, that it is impossible to trace the 

 formation in that direction. There do not seem to be any reasons 

 why the Chazy sea should not have invaded the continent from that 

 direction, and, to the writer, such a land and sea pattern seems more 

 natural than the long narrow fiords which have been premised by 

 recent writers. It seems more probable that the long narrow tracts 

 of strata now exposed are the results of the accidents of earth-move- 

 ments, in which the strata have been fractured and in-faulted in long 

 narrow zones approximately parallel to the coast line. 



THE PELECYPODA. 

 Introduction. 



Pelecypods are not very numerous in the Chazy and they are almost 

 always badly preserved. Usually they occur as casts of the exterior, 

 and thus do not preserve any indications of the hinge-structure or of 

 the muscle-scars. Under such circumstances, accurate determination 

 of the genus is practically impossible, and comparison with other 

 known species is generally useless. Of the species herein described, 

 only three show enough of the internal structure to be of any value, 



1* Bull. Geol. Soc. America, Vol. 21, 1910, p. 677. 



