The Vertical Range of the Intumescens-Fauna. 



The Prenuncial Fauna {Styliola limestone). The name Styliola lime- 

 stone lias been employed in previous papers for a highly bituminous calcareous 

 layer from one to four feet in thickness, which precedes the deposition of 

 the shales and sandstones of the Portage group, and lies near the middle of 

 the Genesee slates. In accordance with a measurement of its exact position 

 in Bell's gully, Canandaigua lake, it would appear to lie at this meridian 

 somewhat above the middle of these beds, with 112-127 feet below and 

 eighty-five feet above it. 



Mr. D. D. Luther found in the section of the Livonia salt shaft, westward 

 of Canandaigua lake, where the thickness of the Genesee formation is notably 

 diminished, that this layer had a thickness of four feet and lies eighty-six feet 

 above the base and seventy-one feet below the top of the formation.* 



The rock sometimes forms a continuous layer, is usually concretionary 

 and often involved with shales, but however it may vary in these respects, a 

 peculiar character is given to it by the myriads of Styliola (Styliolina) 

 fissurella which almost everywhere enter into its composition. This calcareous 

 layer, though thin, represents pretty much all the calcareous matter in these 

 sediments, save that agglomerated into the form of concretions. It is a 

 remarkably persistent formation for one so thin and has been traced from 

 Middlesex, Yates county, to the shore of lake Erie. 



This Styliola limestone plays an important role in our study the fauna of 

 the Intumescens-zone. With the sudden ingress into the shallow seas of the 

 Genesee epoch, of myriads of Styliolinas whose shells have furnished most of 

 the calcareous matter for the limestone, came the first representative of 

 Manticoceras iutumescens, with a considerable company of species unknown 

 before, but, with it, better represented afterward. 



The species of the Styliola limestone are not those of the pre-existing 

 seas of this region but those of the Intumescens-fauna. The majority now 

 appearing for the first time, re-appear in the Naples beds, from which they are 

 here separated by a heavy mass of bituminous, somewhat arenaceous shales. 

 We have elsewhere summarized the correspondence in the fauna of this layer 

 with that of the Naplesf beds and have shown that this first appearance 

 of the Intumescens-fauna was followed by a return of the normal Genesee 

 conditions of sedimentation during which time a virtually complete migration 



* Thirteenth Ann. Rept. N. Y. Slate Geol., vol. 1, j>. 107, 1894. 

 t Fauna with Goniatites Intumescens, etc. 



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