1912.] NATURAL SCIENCES OF PHILADELPHIA. 451 



lower limit of the corals ranges in altitude between 1,000 feet and 

 1,060 feet it is reasonable to assume that the exposures trend not 

 far from the line of strike. The coral beds of the Otisco Valley 

 present certain differences from the Staghorn Point masses. In 

 the first place, the coralline strata are usually thicker, probably 10 

 feet thick at the northernmost exposure examined, while at a ravine 

 cutting across the north and south road which leads to the Otisco 

 causeway 7 we find two beds of corals — a lower one of undetermined 

 thickness at 1,000 feet altitude separated by non-coralline shales 

 from an upper bed which is at least 30 feet thick. The Otisco 

 exposures are for the most part in very narrow gullies choked with 

 debris, and though there can be no doubt that they represent an 

 essentially continuous system, the exact structure is hardly deter- 

 minable. 



The question then naturally arises as to whether or no these 

 Otisco Valley reefs are the contemporaries and the stratigraphic 

 equivalents of the Staghorn Point reefs. Checks with a reliable 

 reference plane are hard to make in the Otisco Valley, but the coral 

 masses appear to lie about 300 feet below the base of the Tully 

 limestone, while in the Skaneateles Valley the corresponding differ- 

 ence is about 360 feet. Considering the great variations in thickness 

 which these coral masses exhibit, we are, it is believed, justified in 

 regarding this evidence as pointing to essential stratigraphic equiva- 

 lency. 



Regarding, then, the Otisco Valley and the Staghorn Point masses 

 as a practically contemporaneous system of coral bodies growing 

 in the same sea, it is advisable to notice here two other Onondaga 

 County exposures — those near the hamlets of Vesper and Joshua 

 (Tully Quadrangle, U. S. G. S.). 



The Vesper Reef is exposed in the Fellows Falls ravine and has 

 been mentioned very briefly by Clarke 8 and Luther as "exposed in 

 the Fellows Falls ravine 3 miles west of Tully. " This bed is about 

 6 feet and 4 inches thick and lies approximately 350 feet below the 

 Tully limestone or in practical agreement with the Staghorn Point 

 reefs. 



The coral layers near Joshua 9 lie at a much higher altitude than 

 any of the others and their exact horizon is much less susceptible of 

 precise determination. They are exposed between the 1,180 and 



7 The causeway is represented in an unfinished condition on the topographic 

 map of the Skaneateles Quadrangle (U. S. G. S.). 



8 Clarke, John M., and Luther, D. D., N. Y. Slate Museum Bull. 82, p. 48. 



9 This is presumably Luther's "Lord's Hill" locality. See pi. 79, Lot 218, 

 in Sweet's New Atlas of Onondaga County, New York, 1874. 



