200 NEW YORK STATE MUSEUM 



relations of which have been a fruitful theme of discussion. 

 The evidence now seems fully to justif}" the interpretation of 

 this deposit as a sediment accumulated in nearly or quite im- 

 pounded fresh w ater or of brackish water cut off from the open sea 

 on the west by a low_, shifting submarine bank, not well defined 

 in the stratigraphy save that outside of it flourished a profuse 

 marine fauna; and on the east continuous with and marking the 

 inception of the Catskill sedimentation. During the period of 

 the existence of these Oneonta beds but few instances appear 

 of incursions from deeper waters. Yet such are not absent. 

 The washing in from the deep water of flotillas of Orthoceras 

 which were appai'ently killed by contact with the fresh water 

 and are preserved in myriads erect in certain of the strata, has 

 been recorded by the writer as evidence of the instability of the 

 outward boundaries of the catchment basin. Other than this 

 these sediments are not known to contain marine fossils. The 

 fishes, Bothriolepis, Coccosteus, Holopt^x-hius, etc. which appear 

 with more or less fi-equency, have not been regarded as 

 of true marine habit; on the contrary, their allies in the 

 Old lied sandstone of Scotland and Russia are distinctive fea- 

 tures of the lakes of that time. There are evidences of ostra- 

 codes and worm trails over the sandy bottoms, but most abun- 

 dant of all forms of life are the accumulated fragments and trunks 

 of Psaroaius, Lepidodendron, Archaeopteris, and other plant 

 remains. 



There are other species of Amnigenia occurring in the Devonic, 

 and these serve to strengthen very substantially the deductions 

 made possible by the New York form- 

 Forbes long ago described^ asAnodonta jukesi, a shell 

 from Kiltorcan, Ireland. Beushausen, who has recently studied 

 specimens of this fossil iu the collections of the Landesanstalt 

 at Berlin, ascribes it to Amnigenia, and notes its occurrence 

 in sandstone beds associated with conglomerates and vari- 

 egated shales underlying the Coal Measures. With regard to 

 these Kiltorcan beds Sir A. Greikie has written as follows^: 



» Oeol. Bur. Ireland. Mem. expl. sbeete 147-57, p. 16, fig. 3a, b. 

 3 Textbook of geology. 1893. p. 802. 



