﻿ART. 
  27 
  

  

  ASYMMETRY 
  IN 
  SKULLS 
  OF 
  MAMMALS 
  HOWELL 
  

  

  11 
  

  

  inward 
  and 
  upward 
  growth 
  of 
  the 
  roots 
  of 
  the 
  tooth 
  and 
  the 
  altera- 
  

   tion 
  of 
  its 
  shape. 
  

  

  Of 
  significance 
  is 
  the 
  practical 
  nondovelopment 
  of 
  the 
  outer 
  ptery- 
  

   goid 
  plate 
  upon 
  the 
  left, 
  following 
  the 
  destruction 
  of 
  function 
  of 
  the 
  

   muscles 
  normally 
  attached 
  to 
  it. 
  A 
  more 
  detailed 
  description 
  of 
  the 
  

   individual 
  bones 
  of 
  the 
  skull, 
  although 
  of 
  interest, 
  is 
  hardly 
  suffi- 
  

   ciently 
  instructive 
  for 
  presentation 
  here. 
  

  

  ASYMMETRICAL 
  SKULLS 
  OF 
  PINNIPEDS 
  

  

  It 
  is 
  through 
  the 
  kindness 
  of 
  Dr. 
  J. 
  Grinnell 
  that 
  the 
  writer 
  has 
  

   been 
  enabled 
  to 
  study 
  the 
  pathological 
  skull 
  of 
  a 
  sea 
  lion 
  from 
  the 
  

   collection 
  of 
  the 
  Museum 
  of 
  Vertebrate 
  Zoology 
  (pis. 
  5,6, 
  and 
  7). 
  

   This 
  is 
  a 
  male 
  specimen 
  of 
  Eumetopias 
  jubata 
  (Schreber), 
  adult 
  

   but 
  not 
  aged, 
  and 
  evidently 
  somewhat 
  stunted 
  by 
  its 
  condition. 
  It 
  

   now 
  bears 
  the 
  data 
  "No. 
  4964, 
  Museum 
  of 
  Vertebrate 
  Zoology, 
  

   July 
  2, 
  1907, 
  Ana 
  Nueva 
  Id., 
  California, 
  John 
  Rowley, 
  257." 
  In 
  

   asymmetry 
  it 
  is 
  far 
  more 
  spectacular 
  than 
  the 
  skull 
  of 
  the 
  gorilla 
  

   already 
  discussed, 
  but 
  its 
  condition 
  is 
  considerably 
  easier 
  of 
  inter- 
  

   pretation. 
  

  

  The 
  specimen 
  was 
  probably 
  shot, 
  as 
  evidenced 
  by 
  a 
  hole 
  in 
  the 
  

   right 
  frontal 
  and 
  a 
  larger 
  one 
  obliquely 
  opposite 
  within 
  the 
  orbit. 
  

   In 
  addition 
  it 
  seems 
  that 
  the 
  skull 
  has 
  since 
  been 
  dropped 
  upon 
  a 
  

   hard 
  surface, 
  for 
  the 
  cranium 
  is 
  badly 
  fractured. 
  John 
  Rowley, 
  the 
  

   collector 
  of 
  the 
  specimen, 
  writes 
  (MS) 
  that 
  it 
  "was 
  apparently 
  as 
  

   fat 
  and 
  husky 
  as 
  any 
  of 
  the 
  others." 
  The 
  only 
  evidence 
  of 
  old 
  scars 
  

   upon 
  the 
  skull 
  is 
  to 
  be 
  found 
  in 
  the 
  posterior 
  half 
  of 
  the 
  left 
  zygo- 
  

   matic 
  arch, 
  and 
  upon 
  the 
  medial 
  portion 
  of 
  the 
  left 
  glenoid 
  fossa. 
  

   It 
  is 
  possible 
  that 
  there 
  was 
  also 
  partial 
  fracture 
  along 
  the 
  suture 
  

   formed 
  by 
  the 
  left 
  jugal 
  with 
  the 
  maxilla, 
  for 
  this 
  is 
  now 
  obliter- 
  

   ated, 
  whereas 
  it 
  is 
  strongly 
  defined 
  upon 
  the 
  opposite 
  side. 
  

  

  Although 
  no 
  full 
  tables 
  of 
  measurements 
  of 
  the 
  four 
  skulls 
  herein 
  

   discussed 
  have 
  been 
  thought 
  necessary, 
  a 
  number 
  of 
  the 
  most 
  signifi- 
  

   cant 
  ones 
  of 
  the 
  abnormal 
  sea 
  lion, 
  compared 
  with 
  a 
  normal 
  one 
  

   which 
  is 
  somawhat 
  larger, 
  but 
  probably 
  of 
  about 
  the 
  same 
  age, 
  are 
  

   found 
  to 
  be 
  of 
  interest. 
  

  

  Total 
  length 
  

  

  Rostral 
  width 
  

  

  Exoccipital 
  to 
  anterior 
  border 
  of 
  canine 
  \]tft 
  

  

  Length 
  of 
  jugal 
  {left*!:: 
  

  

  Total 
  length 
  mandibular 
  ramus 
  1 
  lpft 
  " 
  

  

  Normal 
  

   male 
  

  

  