﻿Report 
  of 
  the 
  State 
  Geologist. 
  851 
  

  

  Rensselseria 
  Cayuga, 
  sp. 
  nov. 
  

   (Plate 
  lxxv, 
  figs. 
  1-4.) 
  

  

  Shell 
  lenticular, 
  often 
  of 
  large 
  size 
  ; 
  suboval 
  in 
  marginal 
  out- 
  

   line. 
  Yalves 
  subequally 
  biconvex, 
  sloping 
  regularly 
  in 
  all 
  

   directions 
  , 
  Apex 
  of 
  the 
  pedicle- 
  valve 
  scarcely 
  prominent 
  ; 
  umbo 
  

   not 
  conspicuous, 
  somewhat 
  elevated 
  medially. 
  Divergent 
  

   cardinal 
  ridges 
  and 
  cardinal 
  slopes 
  well 
  defined. 
  Brachial 
  

   valve 
  with 
  apex 
  depressed 
  and 
  concealed 
  ; 
  somewhat 
  less 
  convex 
  

   in 
  the 
  umbonal 
  region 
  than 
  the 
  opposite 
  valve. 
  Surface 
  of 
  both 
  

   valves 
  covered 
  with 
  a 
  great 
  number 
  of 
  fine, 
  simple, 
  thread-like, 
  

   rarely 
  duplicating 
  plications, 
  of 
  which 
  from 
  seventy 
  to 
  one 
  hun- 
  

   dred 
  may 
  be 
  counted 
  on 
  each 
  valve 
  near 
  the 
  anterior 
  margin. 
  

  

  Oriskany 
  sandstone. 
  Cayuga, 
  Ontario. 
  

  

  Beecheria 
  Davidsoni, 
  sp. 
  nov. 
  

   (Plate 
  lxxix, 
  figs. 
  36-39.) 
  

   (See 
  page 
  300, 
  fig. 
  224.) 
  

  

  