300 H. S. WILLIAMS PERSISTENCE OF FLUCTUATING VARIATIONS 



mapped in the Watkins Glen-Catatonk folio) the first recurrent Tropi- 

 doleptus zone. This zone is typically represented in the section at Van 

 Etten and contains Ehipidomella in 17 localities in the area examined. 

 This zone is in the upper part of the Enfield member of the Portage, 

 below the first appearance of the Chemung fauna in the section. 



OWEGO ZONE 



Four hundred feet above the Van Etten zone the Owego, or second 

 recurrent Tropidoleptus, zone appears. This zone is about 200 feet above 

 the first appearance of the Chemung fauna and 400 feet below the top 

 of the Cayuta member of the Chemung. 



SWARTWOOD ZONE 



This zone is the third recurrent Tropidoleptus zone of the folio and 

 lies at the top of the Cayuta member. In this particular area no Spirifer 

 disjunctus has been discovered above the Swartwood zone. 



Eecurrent Tropidoleptus Fauna in the Watkins Glen-Catatonk 



Folio 



Careful search has been made of every fossiliferous section over the 

 8 15-minute topographic quadrangles making up the area of the Watkins 

 Glen-Catatonk folio, and in 34 loqalities samples of Ehipidomella have 

 been obtained, all in association with other species representing the gen- 

 eral recurrent Tropidoleptus fauna. In some cases only two or three 

 specimens are in evidence; in the majority of cases, however, from 10 to 

 12 or more good specimens for measurement are in evidence. 



Distribution of Sample Sets by Zones 

 The number of different sample sets is as follows for the several zones : 



Ithaca 2 



Van Etten 17 



Owego 6 



Swartwood 9 



For the Hamilton zone a large collection of specimens obtained by 

 H. H. Smith from the shore of Cayuga Lake furnishes the specimens for 

 the series here recorded. The figures given by Hall of the type specimens 

 of the Hamilton species of N"ew York State were also measured for com- 

 parison. In all there are 35 sets of samples, each set from a particular 



