THE AMERICAN NATURALIST [Vol. XLIII 



type material is reported by its original describer as 

 having come from the Livonia salt shaft, Livingston 

 County, N. Y., and its geological horizon is about forty 

 feet above the base of the Marcellus Shale. It lies just 

 below the Stafford Limestone bed of the Marcellus in a 

 black shale and its associates make a typically Marcellus 

 assemblage. Among them are such invertebrates as 

 Orthoceras subulatum, Styliolhia fissurcUa, Chonetes 

 mucronatus, Leiopteria Icevis and Leiorhynchns limi- 

 taris. 9 The cranial fragment figured by Dr. Eastman 10 

 is reported as having come from the Agoniatites Lime- 

 stone, Hendrick's Ledge, west of Manlius, Onondaga 

 County, N. Y. 



The Agoniatites Limestone in Onondaga County lies 

 about thirteen feet above the base of the Marcellus forma- 

 tion, is about two and one half feet thick and is both 

 underlaid and overlaid by the black friable Marcellus 

 shales. 11 The specimen which has been the subject of 

 this brief paper was found in a limy concretion from the 

 upper black shale above the Agoniatites Limestone and 

 probably within ten feet of it. At this point both the 

 shales and the concretions are alike very poor in fossi ] s, 

 none having been found in the shale and a single Ichthyo- 

 dorulite being the only yield from an examination of 

 many other concretions. 



From the evidence of stratigraphy it appears that the 

 limestone lentils of the Marcellus shales are the expres- 

 sions of changing geographical conditions and invading 

 faunas. 12 They are not everywhere at the same geolog- 

 ical horizons with relation to the base of the Marcellus, 

 and as they represent invasions the limestone in one 

 locality may be cotemporaneous with shale in a different 



"D. D. Luther. Eeport on the Livonia Salt Shaft. Kep. State Geol. 

 N. Y., 1893, p. 81. 



10 New Tori- State Mus. Mem., 10, pi. 10. 



11 John M. Clarke. Marcellus Limestone of Central and Western New 

 York and their Faunas. N. Y. State Mus. Bull., 49. 



12 N. Y. State Mus. Bull., 82, p. 43. The Agoniatites Limestone does 



advertently stated on p. 129, N. Y. State Mus. Mem., 10. 



