1912.] NATURAL SCIENCES OF PHILADELPHIA. 449 



the reef increases, and we can observe a gradual lateral transition 

 into contemporaneous shale of the typical Hamilton fades. 2 



Sequence of Events. — In interpreting the observed facts we can 

 assume with reasonable certainty that a local shallowing of the 

 Hamilton Sea combined with an introduction of clearer water cur- 

 rents produced the conditions which were favorable to the growth 

 of the corals. The limy shales were followed by communities of 

 corals. During the growth of these beds currents kept a channel 

 excavated in the northern portion of the region of coral *growth. 

 This channel was slowly filled with lime mud derived from the 

 growing reefs and by invading colonies of corals, which latter, 

 however, were never able to maintain their existence for long in the 

 waters of the channel. Lime muds also derived from the reefs 

 spread out for a small space around the northern margin of the 

 area of coral growth. 



When the channel between the two reefs was nearly filled with 

 lime mud, the whole reef area was overwhelmed by fine land-derived 

 clay muds. This effectually stopped the growth of the reefs, exter- 

 minating the corals and reintroducing the prevalent fauna of the 

 Hamilton Seas. 



Correlations. 



As far as the author has been able to learn, the few references to 

 the Staghorn Point coral masses which are to be found in geological 

 literature are rather short and incidental. In view, however, of 

 the advisability of correlating these reefs with one of the various 

 Hamilton coral-bearing beds which occur in other portions of the 

 county and of the State, the author believes it pertinent to mention 

 here such references as are known to him. 



In 1886 Mr. E. B. Knapp, 3 in a paper read before the Educational 

 Council of Onondaga County and published at a later date, speaks 

 of the principal collecting grounds for corals in the local Hamilton. 

 We find also that he gives 6 feet as the thickness of the "old coral 

 reef" at Staghorn Point. 



Schneider, 4 in 1894, speaks very briefly of "the ancient coral reef 

 at Staghorn Point" as an excellent collecting ground for cyatho- 

 phylloid corals, but makes no mention of the size or structure of the 

 reef. 



2 We have good negative evidence that the section above described is near 

 the western limit of the coral masses, for considerable search has failed to disclose 

 any reefs on the western shore of Skaneateles Lake. 



3 Knapp, E. B., Glimpses of the Geology of Onondaga County, p. 5. 



4 .Schneider, P. F., Notes on the Geology of Onondaga County, Syracuse, 1894. 



