NOTES OX PALEOZOIC CRUSTACEANS 107 



disappeared from the area of Britain, survived outside of that 

 area, on the other hand, the higher parts of the upper Old Red 

 sandstone were contemporaneous with a Carboniferous lime- 

 stone fauna which, having appeared beyond the British area, was 

 ready to spread over it as soon as the conditions became favor- 

 able for its invasion. 



During the progress of Prof. C. S. Prosser's field investiga- 

 tions on the Upper Devonic of eastern New York, of which he 

 has given extensive accounts in the loth and 17th annual reports 

 of the state geologist and paleontologist, he sent in from a 

 locality known as Felter's glen, and lying 2i-o- miles sse from 

 Rensselaerville, Albany co., a large number of specimens of an 

 E s t h e r i a, which at the time of his report was not identified 

 except generically^. In the diagram representing the rock suc- 

 cession at this point (station no. 30B) the blue argillaceous shale 

 which carries these fossils is stated as bearing lamellibranchs, the 

 diagram doubtless having been made before the specimens were 

 referred to the writer for identification as cited on p. 258, Since 

 studying these fossils more carefully, I am satisfied of their 

 identity throughout with the typical expression of Estheria 

 membranacea from the Caithness flags. One can not be 

 easily misled with regard to the specific characters of this little 

 phyllopod. Its subcircular form, central apex, straight hinge 

 line in front of and behind the apex, all tend to render it unique 

 in its expression. In the Felter's glen section, following Prof. 

 Prosser's determination, we have the horizon of the Sherburne 

 sandstone (or initial stage of Portage time), to which he ascribes 

 a thickness of (30 feet, overlaid by 40 feet of green shale, at the 

 base of which is the blue clay shale carrying the Estheria. 

 These 40 feet of shale lying above the horizon of the Sherburne 

 sandstone are regarded by Prosser as representing the entire 

 thickness of Ithaca deposits, and are overlaid by red shales and 

 sandstones considered as the base of Oneonta-Catskill sedi- 

 mentation. This section is in the main in accordance with our 

 present views as to the character of the Oneonta-Catskill sedi- 

 ments, which appear in the geologic column constantly earlier, 



^ITtli an. rep't N. Y, state geol.' and pal. p, 257-58. 



