﻿6 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  67 
  

  

  The 
  exposure 
  of 
  the 
  frontals 
  on 
  the 
  vertex 
  of 
  the 
  skull 
  appears 
  to 
  

   be 
  restricted 
  to 
  the 
  protuberance 
  behind 
  the 
  nasal 
  passages. 
  Pos- 
  

   terially 
  the 
  frontals 
  abut 
  against 
  a 
  narrow 
  strip 
  of 
  bone 
  which 
  has 
  

   been 
  referred 
  to 
  as 
  the 
  "interparietal" 
  and 
  anteriorly 
  they 
  are 
  

   sheathed 
  by 
  the 
  nasals. 
  The 
  protuberance 
  separates 
  the 
  posterior 
  

   extremities 
  of 
  the 
  maxillae 
  on 
  the 
  vertex 
  of 
  the 
  skull. 
  Laterally 
  the 
  

   frontals 
  are 
  overspread 
  by 
  the 
  ascending 
  processes 
  of 
  the 
  premaxillae 
  

   and 
  by 
  the 
  horizontally 
  expanded 
  plates 
  of 
  the 
  maxillae. 
  At 
  a 
  lower 
  

   level, 
  a 
  thin 
  plate 
  of 
  the 
  frontal 
  projects 
  laterally, 
  forming 
  the 
  roof 
  of 
  

   the 
  temporal 
  fossa 
  and 
  in 
  front 
  of 
  this 
  each 
  frontal 
  sends 
  out 
  a 
  large 
  

   supraorbital 
  process 
  which 
  contributes 
  a 
  complete 
  osseous 
  roof 
  for 
  

   the 
  orbit. 
  

  

  The 
  construction 
  of 
  the 
  cresentic 
  foramina 
  below 
  the 
  nasal 
  bones 
  in 
  

   the 
  skull 
  of 
  Zarhachis 
  (pi. 
  2) 
  proved 
  very 
  puzzling 
  on 
  first 
  examination. 
  

   In 
  order 
  to 
  obtain 
  more 
  explicit 
  data 
  on 
  the 
  relations 
  of 
  the 
  bones 
  

   involved, 
  it 
  seemed 
  advisable 
  to 
  make 
  a 
  comparative 
  examination 
  of 
  

   the 
  skulls 
  of 
  as 
  many 
  genera 
  of 
  living 
  toothed 
  whales 
  as 
  were 
  available 
  

   for 
  study. 
  In 
  the 
  course 
  of 
  this 
  review 
  skulls 
  were 
  found 
  in 
  various 
  

   stages 
  of 
  growth, 
  and 
  these 
  have 
  cleared 
  up 
  whatever 
  uncertainties 
  

   may 
  have 
  existed 
  in 
  regard 
  to 
  the 
  construction 
  of 
  this 
  portion 
  of 
  the 
  

   brain 
  case. 
  The 
  interpretations 
  herewith 
  given 
  for 
  the 
  bones 
  inclosing 
  

   the 
  nasal 
  passages 
  have 
  been 
  confirmed 
  by 
  direct 
  comparison 
  with 
  

   disarticulated 
  skulls 
  of 
  living 
  dolphins. 
  

  

  In 
  a 
  skull 
  of 
  a 
  young 
  Berardius 
  bairdi 
  (Cat. 
  No. 
  14218, 
  division 
  of 
  

   mammals, 
  U.S.N.M.) 
  from 
  Bering 
  Island 
  the 
  presphenoid 
  rests 
  in 
  the 
  

   trough 
  of 
  the 
  vomer 
  and 
  the 
  thin 
  lateral 
  walls 
  of 
  the 
  vomer 
  embrace 
  

   the 
  lower 
  half 
  of 
  this 
  bone. 
  Dorsally, 
  there 
  is 
  a 
  second 
  platelike 
  bone 
  

   coextensive 
  with 
  the 
  nasal 
  passage 
  which 
  fits 
  into 
  a 
  groove 
  on 
  the 
  

   upper 
  margin 
  of 
  the 
  lateral 
  wall 
  of 
  the 
  vomer 
  and 
  sheathes 
  the 
  upper 
  

   half 
  of 
  the 
  presphenoid. 
  One 
  of 
  these 
  platelike 
  bones 
  is 
  present 
  in 
  

   each 
  nasal 
  passage. 
  These 
  bones 
  fulfill 
  the 
  requirements 
  of 
  the 
  ect- 
  

   ethmoids. 
  Posteriorly, 
  each 
  ectethmoid 
  meets 
  the 
  corresponding 
  

   frontal 
  edge 
  to 
  edge 
  on 
  the 
  outer 
  border 
  of 
  the 
  frontal 
  fontanelle. 
  

   In 
  older 
  individuals 
  the 
  dorsal 
  margins 
  of 
  the 
  anteriorly 
  directed 
  

   ectethmoids 
  meet 
  on 
  the 
  mid 
  line 
  and 
  fuse 
  with 
  a 
  perpendicular 
  plate 
  

   of 
  bone 
  which 
  extends 
  forward 
  from 
  the 
  base 
  of 
  the 
  nasals 
  to 
  a 
  point 
  

   in 
  front 
  of 
  the 
  nasal 
  passages, 
  thus 
  completely 
  inclosing 
  the 
  pre- 
  

   sphenoid. 
  The 
  thin 
  longitudinal 
  perpendicular 
  plate 
  either 
  represents 
  

   the 
  mesethmoid 
  or 
  a 
  dorsal 
  prolongation 
  of 
  the 
  combined 
  ectethmoids. 
  

   With 
  age, 
  these 
  lateral 
  ectethmoids 
  sheath 
  the 
  internal 
  borders 
  of 
  

   the 
  frontals 
  and 
  extend 
  upward 
  on 
  the 
  posterior 
  walls 
  of 
  the 
  nasal 
  

   passages 
  until 
  they 
  meet 
  the 
  anterior 
  margins 
  of 
  the 
  nasal 
  bones 
  from 
  

   below. 
  Minute 
  foramina 
  are 
  sometimes 
  present 
  in 
  these 
  bones 
  in 
  

   some 
  of 
  the 
  genera 
  of 
  living 
  porpoises. 
  

  

  