﻿8 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  67 
  

  

  Grampus 
  skull, 
  the 
  dorsal 
  margins 
  of 
  the 
  lateral 
  platelike 
  bones 
  or 
  

   octethmoids 
  do 
  not 
  meet 
  above 
  the 
  presphenoid 
  as 
  in 
  an 
  older 
  in- 
  

   dividual 
  and 
  above 
  the 
  level 
  of 
  the 
  latter 
  there 
  is 
  a 
  fissure 
  which 
  

   extends 
  inward 
  from 
  the 
  internal 
  margin 
  of 
  each 
  ectethmoid 
  to 
  the 
  

   rudimentary 
  foramen 
  for 
  the 
  nerve. 
  In 
  addition 
  to 
  this 
  fissure, 
  there 
  

   is 
  a 
  shallow 
  groove 
  leading 
  upward 
  from 
  the 
  foramen 
  and 
  passing 
  

   obliquely 
  across 
  the 
  upper 
  extremity 
  of 
  the 
  ectethmoid. 
  The 
  

   ectethmoid 
  has 
  enveloped 
  the 
  foramen. 
  In 
  other 
  mammals, 
  the 
  

   nasal 
  branch 
  of 
  the 
  ophthalmic 
  division 
  of 
  the 
  fifth 
  cranial 
  nerve 
  

   I 
  > 
  asses 
  outward 
  on 
  each 
  side 
  of 
  the 
  mesethmoid 
  between 
  the 
  latter 
  

   and 
  the 
  ectethmoid. 
  

  

  A 
  critical 
  examination 
  of 
  the 
  Zarhachis 
  skull 
  (pi. 
  2) 
  shows 
  that 
  the 
  

   ectethmoid 
  in 
  the 
  region 
  of 
  the 
  crescentic 
  foramen 
  is 
  more 
  noticeably 
  

   modified 
  than 
  is 
  the 
  case 
  in 
  the 
  skull 
  of 
  the 
  young 
  Grampus. 
  As 
  in 
  

   the 
  latter, 
  a 
  fissure 
  extends 
  inward 
  from 
  the 
  internal 
  margin 
  of 
  the 
  

   ectethmoid 
  to 
  the 
  foramen, 
  but 
  the 
  whole 
  bone 
  is 
  more 
  or 
  less 
  in- 
  

   voluted. 
  Each 
  ectethmoid 
  in 
  the 
  region 
  of 
  these 
  crescentic 
  orifices 
  

   is 
  twisted 
  almost 
  at 
  right 
  angles 
  to 
  the 
  main 
  body 
  of 
  the 
  bone. 
  The 
  

   curvature 
  of 
  the 
  ectethmoid 
  around 
  the 
  foramen 
  is 
  so 
  unusual 
  in 
  

   appearance 
  that 
  one 
  might 
  view 
  the 
  semiovoidal 
  rostral 
  border 
  or 
  

   the 
  margin 
  which 
  is 
  visible 
  on 
  plate 
  2 
  as 
  being 
  actually 
  the 
  outer 
  

   margin 
  of 
  the 
  ectethmoid, 
  and 
  the 
  that 
  border 
  which 
  surrounds 
  the 
  

   foramen 
  at 
  the 
  bottom 
  or 
  at 
  the 
  caudal 
  end 
  of 
  the 
  deep 
  crescentic 
  

   aperture 
  is 
  the 
  internal 
  margin. 
  If 
  this 
  is 
  the 
  true 
  explanation, 
  then 
  

   the 
  flattened 
  condition 
  of 
  the 
  ectethmoid 
  in 
  living 
  porpoises 
  is 
  a 
  later 
  

   development 
  and 
  is 
  indicative 
  of 
  one 
  of 
  the 
  methods 
  by 
  which 
  the 
  

   closure 
  of 
  the 
  foramen 
  has 
  been 
  effected, 
  with 
  the 
  accompanying 
  loss 
  

   of 
  the 
  sense 
  of 
  smell. 
  It 
  should 
  also 
  be 
  noted 
  that 
  the 
  thin 
  per- 
  

   pendicular 
  plate 
  extending 
  from 
  the 
  nasals 
  to 
  a 
  point 
  in 
  front 
  of 
  the 
  

   nasal 
  passages 
  has 
  been 
  destroyed. 
  

  

  The 
  dorsal 
  border 
  of 
  the 
  anterior 
  wall 
  of 
  each 
  nasal 
  passage 
  is 
  very 
  

   thin 
  and 
  projects 
  dorsally 
  for 
  15 
  mm. 
  or 
  more 
  above 
  the 
  porous 
  plug- 
  

   like 
  portion 
  of 
  the 
  presphenoid. 
  Although 
  a 
  number 
  of 
  genera 
  of 
  

   toothed 
  whales 
  were 
  studied, 
  no 
  skulls 
  were 
  found 
  in 
  which 
  the 
  

   construction 
  of 
  the 
  nasal 
  passages 
  corresponded 
  to 
  the 
  Zarhachis 
  type 
  

   of 
  architecture. 
  In 
  Phocaena 
  (Cat. 
  No. 
  3659), 
  Tursiops 
  (Cat. 
  No. 
  

   22299), 
  and 
  Lipotes 
  (Cat. 
  No. 
  218293), 
  the 
  dorsal 
  margin 
  of 
  the 
  

   anterior 
  wall 
  of 
  each 
  nasal 
  passage 
  is 
  formed 
  by 
  a 
  portion 
  of 
  the 
  

   internal 
  border 
  of 
  the 
  maxilla. 
  In 
  all 
  the 
  toothed 
  whales 
  examined, 
  

   the 
  maxilla 
  contributes 
  part 
  of 
  the 
  anterior 
  wall 
  of 
  the 
  nasal 
  passage 
  

   and, 
  with 
  the 
  exception 
  of 
  Inia 
  and 
  Stenodelphis, 
  it 
  always 
  constitutes 
  

   the 
  upper 
  border 
  of 
  the 
  anterior 
  wall. 
  In 
  Inia 
  and 
  Stenodelphis, 
  

   however, 
  the 
  premaxillae 
  are 
  thickened 
  dorso-ventrally 
  and 
  closely 
  

   approximated 
  at 
  the 
  base 
  of 
  the 
  mesorostral 
  gutter; 
  they 
  constitute 
  

   the 
  upper 
  border 
  of 
  the 
  nasal 
  passages. 
  In 
  Zarhachis, 
  however, 
  at 
  

  

  