594 HENRY SHALER WILLIAMS 



far as the formation can be traced and identified by means of its 

 lithologic character, its stratigraphic association, and its contained 

 fossils." But the member or lentil is a "specially developed part" 

 of a formation; it is therefore considered inappropriate to apply 

 the member or lentil name in absence of the characters distinguishing 

 it. 



For these reasons the terms "West River shale," " Cashaqua 

 shale," "Parrish Hmestone," "Rhinestreet black shale," "Hatch 

 shale and flags," used by Clarke and Luther,' are not deemed appro- 

 priate names to apply to portions of the Nunda formation of the 

 Watkins or Ithaca quadrangles, hov^ever appropriate they may be 

 for the sections of Canandaigua Lake or in the Genesee Valley. 



Paleontological definition of the Nunda. — Paleontologically the 

 Nunda formation is well characterized by the fauna ascribed to it 

 by Hall in the Fourth District report of 1843 (pp. 241-47). The 

 species named by him are (giving the original names): Fucoides 

 graphica, Fucoides verticalis, Avlcula speciosa, Ungulina suborbi- 

 culariSj Bellerophon expansus^ Orthoceras aciculum, Clymenia com- 

 planta, Goniatites sinuosus, Pinnopsis acutirostra, Pinnopsis ornatus^ 

 Delthyris Icevis, Cardium? vetustum, Orthis tenuistriata, Lucina 

 retusa, Nucula lineolata, Astarte subtextilis, Bellerophon striatus 

 (Bronn, Philhps), Goniatites bicostatus, and Cyathocrinus ornatis- 

 simus. These nineteen species have been more definitely defined 

 and named, and a great number of other species have been added 

 to them since 1843, but they clearly indicate the fauna. There are 

 in Hall's fist eight Pelecypoda, two Gastropoda, four Cephalopoda, 

 two Brachiopoda, one Echinodermata, and two of uncertain classi- 

 fication. About 75 per cent, are Mollusca. Later study of the 

 fauna shows the same dominance of this class. The Brachopods 

 are conspicuous by their absence ; and it is the dominance of Brach- 

 ipods in the Ithaca fauna which distinguishes the zone in which 

 they occur as a well-marked member of the formation. Litho- 

 logically the Ithaca rocks are not clearly distinguishable from the 

 other rocks of the Nunda formation of this section, though they are 

 paleontologically. This Nunda fauna was definitely recognized 



I "Geology of the Watkins and Elmira Quadrangle," by John M. Clarke and 

 A. Dana Luther, New York State Museum., Bulletin No. 8i, 1905. 



