﻿ANNIVERSARY 
  ADDRESS 
  OF 
  THE 
  PRESIDENT. 
  23 
  1 
  

  

  Phylloceras 
  commences 
  in 
  the 
  Trias 
  ; 
  but 
  no 
  British 
  Triassic 
  species 
  

   is 
  known. 
  P. 
  Loscombi, 
  Sow., 
  occurs 
  in 
  the 
  British 
  Middle 
  Lias 
  ; 
  

   and 
  P. 
  heteropTiyllum, 
  Sow., 
  and 
  P. 
  subcarinatum, 
  Young, 
  in 
  the 
  

   Upper 
  Lias. 
  In 
  the 
  Cretaceous 
  rocks 
  the 
  only 
  British 
  forms 
  are 
  

   P. 
  Velledce 
  and 
  P. 
  lewesiense. 
  

  

  Fam. 
  IV. 
  iEGOCERATiD^. 
  

  

  Includes 
  several 
  groups 
  having 
  widely 
  different 
  forms. 
  

   This 
  family 
  is 
  divided 
  into 
  3 
  subfamilies 
  : 
  — 
  

  

  Subfam. 
  1. 
  JEgoceratites. 
  

  

  2 
  genera 
  : 
  Arietites 
  and 
  JEgoceras. 
  

  

  Subfam. 
  2. 
  Earpoceratites. 
  

  

  3 
  genera 
  : 
  Harpoceras, 
  Oppelia, 
  and 
  Haploceras. 
  

  

  Subfam. 
  3. 
  Stephanoceratites. 
  

  

  15 
  genera 
  : 
  StcpJianoceras, 
  Cosmoceras, 
  Ancyloceras, 
  Baculina, 
  

   Simoceras, 
  Perisphinctes, 
  Oleostephanus, 
  ScapJiites, 
  Hoplites, 
  Acan- 
  

   thoceras, 
  Stoliczkaia, 
  Grioceras, 
  Heteroceras, 
  Peltoceras, 
  and 
  Aspido- 
  

   ceras. 
  

  

  Subfam. 
  1. 
  JEgoceratites. 
  

  

  Genus 
  JEgoceras, 
  a 
  large 
  and 
  important 
  genus 
  in 
  the 
  British 
  rocks, 
  

   especially 
  in 
  the 
  Lower 
  and 
  Middle 
  Lias. 
  JEgoceras 
  may 
  be 
  divided 
  

   into 
  4 
  sections 
  based 
  upon 
  the 
  structure 
  of 
  the 
  shell. 
  

  

  Section 
  I. 
  Psilonoti. 
  

   „ 
  2. 
  Angidati. 
  

   „ 
  3. 
  Armati. 
  

   „ 
  4. 
  Involuti. 
  

  

  Sect. 
  1. 
  Psilonoti. 
  — 
  Essentially 
  Lower 
  Lias 
  and 
  in 
  the 
  lowest 
  

   zone 
  (Planorbis). 
  

  

  In 
  all 
  the 
  species 
  of 
  this 
  section 
  the 
  keel 
  is 
  absent, 
  and 
  there 
  are 
  

   no 
  lateral 
  longitudinal 
  channels 
  in 
  the 
  siphonal 
  or 
  ventral 
  area. 
  The 
  

   lobe-line 
  is 
  much 
  ramified, 
  and 
  the 
  lobes 
  are 
  complicated. 
  The 
  species 
  

   are 
  the 
  well-known 
  forms 
  JEg. 
  planorbis, 
  Sow., 
  JEg. 
  Johnstoni, 
  

   Sow., 
  JEg. 
  torus, 
  D'Orb., 
  JEg. 
  intermedium, 
  Portl., 
  JEg. 
  Belcheri, 
  

   Simp., 
  and 
  2Eg. 
  liassicum, 
  D'Orb. 
  These 
  forms 
  all 
  occur 
  in 
  the 
  

   zone 
  of 
  JEg. 
  planorbis, 
  at 
  the 
  extreme 
  base 
  of 
  the 
  Lias. 
  They 
  range 
  

   through 
  Britain 
  wherever 
  these 
  lowest 
  beds 
  are 
  observed. 
  

  

  Sect. 
  2. 
  Angulati. 
  — 
  This 
  is 
  an 
  extremely 
  well-defined 
  section. 
  

   The 
  sharply 
  flexed 
  ribs 
  and 
  deep 
  channel 
  on 
  the 
  ventral 
  area 
  distin- 
  

   guish 
  the 
  species 
  of 
  JEgoceras 
  belonging 
  to 
  this 
  section. 
  The 
  chief 
  

   species 
  are 
  JEg. 
  angidatum, 
  JEg. 
  Cliarmassei, 
  and 
  JEg. 
  catenatum, 
  

   all 
  of 
  which 
  occur 
  in 
  the 
  zone 
  of 
  JEg. 
  angidatum. 
  JEg. 
  lacunatum 
  

   and 
  JEg. 
  Boucaultianum, 
  D'Orb., 
  with 
  JEg. 
  Birchii, 
  are 
  from 
  the 
  

   succeeding 
  or 
  higher 
  zone 
  of 
  Arietites 
  Bucklandi, 
  the 
  whole 
  being 
  

   Lower 
  Lias 
  and 
  British. 
  

  

  