RECORDS OF MEETINGS OF 1906 267 



has been covered by old andesitic eruptives; that continental movements 

 have raised, tilted, faulted and metamorphosed the limestone, producing 

 schists from clayey beds; that granite has been intruded under and into 

 the limestone; that later and more acid lavas (rhyolites) and tuffs have 

 been poured out or deposited over the regit)n; that the latest outflows were 

 of basaltic lavas; that the local conglomerates and sandstones have been 

 formed in constructional basins by the disintegration of the mountain 

 slopes. Many other points of geologic interest were brought out in the 

 photographs. 



Professor Grabau said that recent examination of the limestones of the 

 Mackinaw region for the Michigan Geologic Survey, showed the existence 

 of the Schoharie fauna in the basal portion of the Dundee formation, in 

 a number of localities in the northern part of lower Michigan; notably at 

 Mill Creek, near Mackinaw City, and on Mackinaw Island. Such typical 

 species as Trochoceras clio, Atrypa impressa, Rhipidomella alea, Cono- 

 cardeum cuneus, Phacops cristatus, etc., characterize this fauna. The 

 strata containing it rest directly upon beds with Leperditia opscalaris, and, 

 therefore, of lower Manlius (Greenfield limestone, Cobleskill) age, from 

 which they are separated by a pronounced disconformity. The finding 

 of this fauna fixes the date of the great mid-Devonic transgression. 



Dr. Kunz pointed out the general features of the occurrence of diamonds 

 in North America, reserving more complete discussion for the next meeting. 



The meeting then adjourned. 



A. W. Grabau, 



Secetary. 



SECTION OF BIOLOGY. 

 January 15, 1906. 



Section met at 8: 15 P. M., at the American Museum of Natural History, 

 Vice-President Crampton presiding. 



The minutes of the preceding meeting were read and approved. 

 The following program was then offered. 



William Beutenmiiller, The South American Species of Moths Belong- 

 ing TO THE Genus Attacus. 



R. C. Osbum, Some Experiments on Dragon Flies in Brackish 



Water. 



