﻿art. 
  28 
  SKULL 
  OK 
  ZARHACHIS 
  FLAGELLATOR 
  KELLOGG 
  5 
  

  

  and 
  their 
  posterior 
  margins 
  form 
  a 
  continuous 
  curve 
  with 
  the 
  pos- 
  

   terior 
  border 
  of 
  the 
  protuberance 
  behind 
  the 
  nasal 
  passages. 
  There 
  

   is 
  a 
  relatively 
  large 
  dorso-ventrally 
  compressed 
  foramen 
  in 
  the 
  max- 
  

   illa 
  at 
  the 
  posterior 
  extremity 
  of 
  the 
  prcmaxilla 
  which 
  opens 
  into 
  a 
  

   short, 
  deep 
  groove. 
  

  

  In 
  the 
  preceding 
  paper 
  it 
  was 
  stated 
  that 
  "skulls 
  of 
  Lipotes 
  and 
  

   Inia. 
  may 
  appear 
  more 
  specialized 
  than 
  that 
  of 
  Zarliachis 
  4 
  because 
  

   of 
  the 
  elevation 
  of 
  the 
  vertex 
  and 
  the 
  shifting 
  of 
  the 
  nasals 
  to 
  a 
  

   vertical 
  position." 
  This 
  opinion 
  was 
  based 
  upon 
  a 
  small 
  fragment 
  

   of 
  bone 
  which 
  appeared 
  to 
  represent 
  a 
  portion 
  of 
  the 
  vertex. 
  Fur- 
  

   ther 
  on 
  5 
  it 
  was 
  said 
  that 
  "this 
  fragment 
  is 
  very 
  important, 
  for 
  it 
  

   shows 
  that 
  the 
  vertex 
  of 
  the 
  skull 
  was 
  not 
  strongly 
  elevated, 
  or 
  at 
  

   least 
  no 
  prominent 
  protuberance, 
  like 
  in 
  Inia 
  or 
  Lipotes, 
  was 
  pres- 
  

   ent." 
  On 
  reexamination 
  it 
  has 
  been 
  found 
  that 
  this 
  fragment 
  differs 
  

   in 
  a 
  number 
  of 
  respects 
  from 
  the 
  vertex 
  of 
  the 
  second 
  skull. 
  The 
  pro- 
  

   tuberance 
  behind 
  the 
  nasal 
  passages 
  may 
  have 
  changed 
  with 
  age 
  and 
  

   varied 
  according 
  to 
  sex. 
  Nevertheless 
  certain 
  peculiarities 
  of 
  this 
  

   fragment 
  are 
  not 
  readily 
  interpreted 
  on 
  the 
  basis 
  of 
  conditions 
  in 
  the 
  

   second 
  skull, 
  and 
  there 
  are 
  some 
  features 
  which 
  suggest 
  the 
  inter- 
  

   pretation 
  given 
  in 
  the 
  preceding 
  paper. 
  This 
  second 
  skull, 
  however, 
  

   shows 
  that 
  other 
  portions 
  of 
  the 
  attempted 
  restoration 
  are 
  incorrect 
  

   and 
  also 
  that 
  the 
  protuberance 
  behind 
  the 
  nasal 
  passages 
  is 
  broader 
  

   than 
  in 
  Inia 
  and 
  Lipotes. 
  

  

  The 
  nasal 
  bones 
  do 
  not 
  overhang 
  the 
  nasal 
  passages; 
  their 
  antero- 
  

   posterior 
  diameter 
  is 
  about 
  equivalent 
  to 
  one-half 
  of 
  their 
  breadth. 
  

   The 
  nasals 
  are 
  applied 
  to 
  the 
  anterior 
  surfaces 
  of 
  the 
  frontals, 
  as 
  in 
  

   Lipotes 
  and 
  Inia, 
  but 
  they 
  are 
  proportionately 
  larger 
  bones 
  and 
  

   actually 
  increase 
  the 
  size 
  of 
  the 
  protuberance 
  behind 
  the 
  nasal 
  pas- 
  

   sages. 
  From 
  a 
  dorsal 
  view 
  the 
  nasals 
  are 
  almost 
  subtriangular 
  in 
  

   outline, 
  but 
  the 
  posterior 
  margin 
  is 
  more 
  or 
  less 
  emarginate 
  and 
  the 
  

   anterior 
  concave. 
  Inferiorly 
  they 
  are 
  overspread 
  by 
  the 
  extremities 
  

   of 
  the 
  ectethmoids. 
  In 
  the 
  case 
  of 
  Inia 
  and 
  Lipotes 
  the 
  nasals 
  con- 
  

   sist 
  of 
  thin 
  plates 
  of 
  bone 
  applied 
  to 
  the 
  anterior 
  surface 
  of 
  the 
  pro- 
  

   tuberance 
  behind 
  the 
  nasal 
  passages, 
  and 
  their 
  dorsal 
  margins 
  do 
  

   not 
  extend 
  upward 
  to 
  the 
  level 
  of 
  the 
  dorsal 
  surfaces 
  of 
  the 
  frontals. 
  

  

  A 
  narrow 
  interparietal 
  may 
  be 
  present 
  between 
  the 
  crest 
  of 
  the 
  

   supraoccipital 
  and 
  the 
  protuberance 
  behind 
  the 
  nasal 
  passages. 
  A 
  

   narrow 
  groove 
  follows 
  the 
  posterior 
  border 
  of 
  this 
  protuberance, 
  and 
  

   may 
  possibly 
  represent 
  a 
  suture 
  between 
  the 
  combined 
  frontals 
  and 
  

   the 
  narrow 
  strip 
  of 
  bone 
  which, 
  because 
  of 
  its 
  position, 
  may 
  very 
  well 
  

   represent 
  the 
  interparietal. 
  An 
  interparietal 
  seems 
  to 
  be 
  present 
  in 
  

   the 
  skull 
  of 
  Inia 
  geofrensis 
  (Cat. 
  No. 
  239667, 
  U.SN.M.). 
  Both 
  con- 
  

   dyles 
  are 
  visible 
  when 
  the 
  skull 
  is 
  viewed 
  from 
  above. 
  

  

  ' 
  Kellogg, 
  R., 
  Proc. 
  U. 
  S. 
  Nat. 
  Mus., 
  vol. 
  63, 
  1924, 
  p. 
  7. 
  

   * 
  Kellogg, 
  R., 
  Idem, 
  p. 
  13. 
  

  

  