60 PBOCEEDIlsrGS OF THE NATIONAL MUSEUM vol.76 



ing formations in eastern North America and Europe. But the 

 greater part of both of these faunas is so much more like that of the 

 Lenoir and those of the Lower and Middle Chazy of the Champlain 

 and St. Lawrence valleys that common origin for all of them seems 

 highly probable. But where the bulk of these Middle Chazyan, Lit- 

 tle Oak, and Chambersburg faunas originated and by what paths 

 they reached Pennsylvania, Virginia, and Alabama can as yet be 

 explained only by conjecture*. Some of the Champlain Chazy species 

 suggest a northern origin, though hardly Arctic, and it may be that 

 they migrated from there by way of the Champlain Valley to the 

 west side of the middle Atlantic basin. Or they may have gotten 

 to inland troughs that are now buried beneath the Coastal Plain 

 south of New York in which they attained and for some time main- 

 tained a foothold. The available evidence suggests further that the 

 Chambersburg invasion of the Appalachian Valley came from these 

 more eastern, probably Piedmont and subcoastal plain troughs. 



Origin of Trenton and late Black River faunas. — In this connec- 

 tion I wish to call attention also to the Trenton faunas of Ontario, 

 New York, New Jersey and Pennsylvania, and to make the general 

 statement that all but one of these faunas is very different from those 

 of the corresponding Trenton group of formations in Tennessee and 

 Kentucky. Excepting the crinoid and cystid fauna that is held in 

 common by the first or Curdsville limestone formation of the Trenton, 

 group in Kentucky and the Hull limestone, which is the second of 

 the Trenton formations in Ontario, the Trenton faunas in Kentucky 

 and Tennessee comprise many clearly indicated progenitors of the 

 succeeding Cincinnatian faunas in the same States and like these 

 doubtless invaded the continent from the south. On the contrary, 

 the New York and Ontario Trenton faunas — which not only began 

 their epicontinental record earlier (that is, with the Kockland), but 

 extended their geographical range from Ontario westward to Min- 

 nesota and from there southward to the flanks of the Arbuckle 

 Mountains in Oklahoma — these must have invaded the continent 

 from the northeast or north. And an essentially similar conclusion 

 is forced on us regarding the origin of the late Black River Decorah 

 faunas that underlie the Trenton formations in the Mississippi Val- 

 ley and Ontario. The northern origin of the Decorah faunas is in- 

 ferred and reasonably proved by the total absence south of central 

 Kentucky of beds that, if present, doubtless would contain them. On 

 the other hand, they are present in most if not all of the exposures 

 of rocks of similar age to the north in Canada. Still more convinc- 

 ing is the fact that comparison of Decorah and early Trenton (Pros- 

 ser) faunas in the Upper Mississippi Valley with Baltic Ordovician 

 faunas discloses many generic similarities, and particularly among 



