﻿392 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [May 
  25, 
  

  

  Berardius, 
  M. 
  Duvernoy 
  employs 
  the 
  term 
  Heterodontes, 
  previously 
  

   used 
  by 
  Desmarest 
  and 
  Lesson. 
  In 
  M. 
  Gervais's 
  subsequent 
  publica- 
  

   tions 
  * 
  he 
  reasserts 
  the 
  identity 
  of 
  Zvphius 
  cavirostris 
  with 
  the 
  Ceta- 
  

   cean 
  of 
  Aresquiers. 
  Not 
  recognizing 
  Mesodiodon, 
  ho 
  includes 
  in 
  

   Dioplodon 
  not 
  only 
  D. 
  densirostris, 
  but 
  a 
  new 
  recent 
  species, 
  D. 
  Eu- 
  

   ropceus, 
  and 
  two 
  fossil 
  species 
  — 
  the 
  Zipliius 
  longirostris 
  (Cuv.), 
  and 
  a 
  

   new 
  species, 
  D. 
  Becanii, 
  founded 
  on 
  the 
  specimen 
  which 
  had 
  been 
  

   regarded 
  by 
  M. 
  Yan 
  Beneden 
  as 
  identical 
  with 
  Zipliius 
  longirostris 
  

   (swpr&i 
  p. 
  389). 
  

  

  M. 
  Gervais 
  adopts 
  Ghoneziphius 
  (Duv.); 
  so 
  that 
  he 
  agrees 
  with 
  

   M. 
  Duvernoy 
  in 
  considering 
  the 
  three 
  Cuvierian 
  species 
  of 
  Zipliius 
  as 
  

   members 
  of 
  as 
  many 
  genera, 
  and, 
  further, 
  in 
  regarding 
  Zipliius 
  lon- 
  

   girostris 
  (Cuv.) 
  as 
  of 
  the 
  same 
  genus 
  with 
  the 
  recent 
  Delphinus 
  

   densirostris. 
  And, 
  so 
  far 
  as 
  Cuvier's 
  original 
  species 
  go, 
  the 
  only 
  

   difference 
  of 
  opinion 
  between 
  M. 
  Gervais 
  and 
  M. 
  Duvernoy 
  is 
  whe- 
  

   ther 
  " 
  Zipliius" 
  longirostris 
  shall 
  be 
  called 
  Dioplodon 
  or 
  Mesodiodon. 
  

   But 
  if 
  the 
  line 
  of 
  argument 
  taken 
  by 
  M. 
  Duvernoy 
  is 
  a 
  correct 
  one, 
  

   and 
  " 
  Zipliius'''' 
  longirostris 
  is 
  generically 
  identical 
  with 
  Delphinus 
  

   micropterus, 
  then 
  it 
  is 
  a 
  Micropteron 
  (Eschricht). 
  On 
  the 
  other 
  

   hand, 
  if 
  Delpliinus 
  densirostris 
  has 
  a 
  claim 
  to 
  generic 
  distinctness 
  

   from 
  D. 
  micropterus 
  and 
  D. 
  Sowerhiensis, 
  as 
  would 
  seem 
  to 
  be 
  the 
  

   case, 
  M. 
  Gervais's 
  name 
  of 
  Dioplodon 
  must 
  stand, 
  and 
  the 
  question 
  

   arises 
  — 
  is 
  " 
  Zipliius'''' 
  longirostris 
  a 
  Dioplodon 
  ? 
  

  

  I 
  am 
  acquainted 
  with 
  the 
  skull 
  of 
  Dioplodon 
  densirostris 
  only 
  by 
  

   the 
  figures 
  given 
  by 
  MM. 
  Duvernoy 
  and 
  Gervais, 
  there 
  being 
  no 
  spe- 
  

   cimen 
  of 
  this 
  rare 
  animal 
  in 
  England, 
  to 
  my 
  knowledge. 
  But 
  these 
  

   figures 
  clearly 
  show 
  (1) 
  that 
  the 
  width 
  of 
  the 
  vomer 
  exposed 
  on 
  the 
  

   upper 
  face 
  of 
  the 
  snout 
  does 
  not 
  nearly 
  attain 
  one-third 
  the 
  whole 
  

   width 
  of 
  that 
  face, 
  and 
  (2) 
  that 
  the 
  vomer 
  terminates 
  before 
  reach- 
  

   ing 
  the 
  end 
  of 
  the 
  rostrum, 
  the 
  premaxillge 
  being 
  separated 
  beyond 
  

   it 
  by 
  a 
  well-marked 
  notch 
  or 
  cleft, 
  so 
  that 
  the 
  end 
  of 
  the 
  snout 
  is 
  

   bifid, 
  as 
  in 
  Cetacea 
  in 
  general. 
  

  

  Now, 
  in 
  all 
  the 
  fossil 
  rostra 
  allied 
  to 
  "Zipliius" 
  longirostris 
  which 
  

   I 
  have 
  examined, 
  or 
  seen 
  figured, 
  the 
  vomer 
  occupies 
  fully 
  a 
  third 
  of 
  

   the 
  width 
  of 
  the 
  upper 
  face 
  of 
  the 
  rostrum 
  ; 
  and 
  in 
  the 
  few 
  instances 
  

   in 
  which 
  the 
  extremity 
  of 
  the 
  rostrum 
  is 
  entire, 
  it 
  is 
  not 
  bifid, 
  but 
  

   sharply 
  pointed, 
  almost 
  like 
  the 
  end 
  of 
  the 
  guard 
  of 
  a 
  Belemnite, 
  the 
  

   vomer 
  and 
  premaxilhe 
  seeming 
  to 
  coalesce 
  into 
  one 
  solid 
  terminal 
  

   cone. 
  

  

  Taking 
  into 
  account 
  these 
  marked 
  differences 
  from 
  any 
  recent 
  

   species, 
  observable 
  in 
  the 
  structure 
  of 
  the 
  beaks 
  of 
  the 
  fossil 
  forms, 
  

   and 
  considering 
  that 
  we 
  know 
  nothing 
  whatever 
  of 
  the 
  mandibular 
  

   dentition 
  of 
  the 
  latter, 
  I 
  think 
  they 
  should 
  be 
  regarded 
  as 
  members 
  

   of 
  a 
  distinct 
  genus, 
  to 
  which 
  the 
  name 
  of 
  Belemnoziphius 
  may 
  be 
  

   applied. 
  And 
  were 
  there 
  not, 
  as 
  I 
  believe 
  there 
  are, 
  sufficient 
  

   zoological 
  grounds 
  for 
  this 
  step, 
  I 
  might 
  urge 
  as 
  a 
  pakeontological 
  

   argument 
  in 
  its 
  favour, 
  the 
  great 
  importance 
  of 
  not 
  passing 
  over 
  too 
  

   lightly 
  any 
  differences 
  which 
  may 
  be 
  observable 
  between 
  the 
  Mam- 
  

   mals 
  of 
  the 
  Crag 
  and 
  those 
  of 
  the 
  present 
  day. 
  

  

  * 
  Zoologie 
  et 
  Paleontologie 
  Frar^aise, 
  ed 
  v 
  2, 
  p. 
  287. 
  

  

  