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NEW YORK STATE MUSEUM 



ground is continuously low, much filled with detritus and specially swampy. 

 The northern reaches of the Oak Orchard swamp, extending from near 

 Churchville, Monroe co. on the east, across Orleans county, are excavated 

 in the Salina shales and have the dolomite series (Guelph and upper 

 Lockport) for a floor. Hence it is not altogether strange that, during the 

 years of geologic study which have elapsed since 1 843, extremely little has 

 been seen of the strata buried in this almost undissected region. 



In 1892 Albert L. Arey brought to the attention of the geologic 

 section of the American Association for the Advancement of Science in 

 session in the city of Rochester, his discovery of a fine series of fossils 

 from this horizon at the top of the Lockport dolomites in and about that 

 city. Some of these were obtained from the uppermost layers in a quarry 

 then being worked in the southwest part of the city and known as the 

 Nellis quarry ; at present writing these workings are abandoned. More 

 were derived from occasional excavations for municipal improvements made 

 in the southern part of the city, affording an opportunity for collecting 

 which may sometime recur but which is beyond the control of the geologist. 

 This fauna was subsequently the subject of study by its discoverer, who 

 published a brief account of it in the Proceedings of the Rochester 

 Academy of Science [1892. 2 : 104-7]. 



These organisms proved to be for the most part preserved in nodules 

 of white chert, of which they have frequently formed the nuclei, but in 

 which more often they had become irregularly involved in the process of 

 segregation. The shells themselves are largely replacements in chalcedonic 

 silica and preserve with fine accuracy and in a manner altogether unusual 

 for paleozoic fossils the important exterior surface ornament. This mode 

 of preservation makes them extraordinarily interesting subjects. In the 

 brief paper cited Mr Arey has brought the fauna as then known to him 

 into comparison with the species of the Canadian Guelph and the published 

 lists of fossils from the Chicago and Racine limestones, and elicits there- 

 from the very close similarity in general composition of the Rochester and 

 Guelph faunas and the striking contrast between the former and the faunas 



