﻿art. 
  27 
  ASYMMETRY 
  IN 
  SKULLS 
  OP 
  MAMMALS 
  HOWELL 
  3 
  

  

  There 
  is 
  described 
  and 
  figured 
  by 
  Paravicius 
  5 
  the 
  skull 
  of 
  a 
  dog 
  

   exhibiting 
  a 
  marked 
  dextral 
  twist 
  to 
  the 
  rostral 
  region. 
  Unfortu- 
  

   nately, 
  this 
  specimen 
  lacked 
  the 
  lower 
  jaw, 
  for 
  the 
  characters 
  strongly 
  

   indicate 
  that 
  the 
  reason 
  for 
  the 
  asymmetrical 
  condition 
  was 
  the 
  sub- 
  

   normal 
  development 
  of 
  the 
  right 
  ramus 
  of 
  the 
  mandible, 
  due 
  to 
  a 
  

   fracture 
  during 
  puppyhood. 
  There 
  is 
  no 
  appreciable 
  asymmetry 
  of 
  

   the 
  temporal 
  fossae. 
  

  

  Toldt 
  e 
  discusses 
  the 
  asymmetrical 
  skull 
  of 
  a 
  fox 
  in 
  the 
  Vienna 
  

   Museun. 
  On 
  account 
  of 
  a 
  diseased 
  condition 
  of 
  the 
  left, 
  lower, 
  fourth, 
  

   premolar 
  the 
  animal 
  had 
  used 
  the 
  temporal 
  muscle 
  of 
  the 
  right 
  side 
  as 
  

   exclusively 
  as 
  possible. 
  The 
  myological 
  condition 
  resulting 
  was 
  a 
  

   slight 
  increase 
  in 
  the 
  size 
  of 
  the 
  right 
  temporal, 
  shifting 
  its 
  ridge 
  a 
  

   bit 
  entad. 
  Atrophy, 
  or 
  rather 
  nondevelopment, 
  of 
  the 
  left 
  temporal 
  

   was 
  marked, 
  its 
  ridge 
  developing 
  considerably 
  laterad 
  of 
  the 
  normal 
  

   position, 
  and 
  there 
  is 
  practically 
  no 
  lambdoidal 
  crest 
  upon 
  that 
  side. 
  

   The 
  left 
  supraorbital 
  process 
  and 
  the 
  portion 
  of 
  the 
  temporal 
  fossa 
  

   immediately 
  caudad 
  thereto, 
  however, 
  are 
  shown 
  in 
  the 
  illustration 
  to 
  

   be 
  better 
  developed 
  upon 
  the 
  left 
  side. 
  A 
  somewhat 
  puzzling 
  circum- 
  

   stance 
  is 
  the 
  fact 
  that 
  in 
  the 
  drawing, 
  the 
  left 
  zygomatic 
  arch 
  is 
  shown 
  

   to 
  be 
  about 
  2 
  mm. 
  farther 
  from 
  the 
  cranium 
  than 
  the 
  right, 
  while 
  the 
  

   text 
  also 
  mentions 
  that 
  the 
  disparity 
  is 
  slight. 
  This 
  state 
  of 
  the 
  left 
  

   zygoma 
  is 
  at 
  variance 
  with 
  what 
  one 
  would 
  naturally 
  expect 
  to 
  

   accompany 
  a 
  reduced 
  temporal 
  muscle. 
  I 
  imagine, 
  however, 
  that 
  

   there 
  was 
  some 
  special 
  disparity 
  between 
  the 
  masseter 
  muscles 
  to 
  

   account 
  for 
  it 
  — 
  an 
  hypothesis 
  which 
  can 
  hardly 
  now 
  be 
  proven. 
  

  

  An 
  instance 
  is 
  mentioned 
  by 
  Leisewitz 
  7 
  of 
  slight 
  asymmetry 
  in 
  the 
  

   skull 
  of 
  a 
  monkey 
  of 
  the 
  genius 
  Lagothrix. 
  The 
  bilateral 
  disparity 
  

   is 
  very 
  poorly 
  defined, 
  however, 
  and 
  the 
  author 
  is 
  mainly 
  concerned 
  

   with 
  consequent 
  slight 
  differences 
  in 
  tooth 
  wear. 
  

  

  The 
  skulls 
  at 
  hand 
  exhibiting 
  definite 
  asymmetry 
  number 
  four. 
  

   Two 
  of 
  them 
  are 
  of 
  primates, 
  whose 
  musculature 
  of 
  mastication 
  is 
  

   adapted 
  to 
  the 
  absence 
  of 
  true 
  glenoid 
  fossas, 
  and 
  hence, 
  to 
  a 
  con- 
  

   siderable 
  movement 
  of 
  the 
  mandible 
  in 
  all 
  directions. 
  The 
  remaining 
  

   two 
  skulls 
  belong 
  to 
  a 
  single 
  species 
  of 
  pinniped 
  — 
  a 
  carnivore 
  having 
  

   true 
  glenoid 
  fossa?, 
  which 
  permits 
  practically 
  no 
  lateral 
  nor 
  propali- 
  

   nal 
  motion 
  of 
  the 
  mandible. 
  

  

  ASYMMETRICAL 
  SKULLS 
  OF 
  PRIMATES 
  

  

  The 
  writer 
  is 
  indebted 
  to 
  Mr. 
  G. 
  S. 
  Miller, 
  jr. 
  for 
  permission 
  to 
  

   study 
  the 
  skull 
  of 
  a 
  form 
  of 
  gorilla 
  in 
  the 
  National 
  Museum 
  collec- 
  

   tion 
  (see 
  pis. 
  3, 
  4, 
  5, 
  and 
  6). 
  This 
  bears 
  the 
  data 
  " 
  No. 
  239883, 
  male, 
  

  

  6 
  Paravicius, 
  Q., 
  Asimmetrie 
  cranio 
  fasciali 
  in 
  un 
  cane, 
  Atti 
  Soc. 
  Ital. 
  scienze 
  nat., 
  1902, 
  pp, 
  349-352. 
  

  

  6 
  Toldt, 
  Von 
  K., 
  Asymmetrische 
  Ausbildung 
  der 
  Schlafenmuskeln 
  bei 
  einen 
  Fuchs 
  infolge 
  einseitigei 
  

   Kautatigkeit, 
  Zool. 
  Anz 
  , 
  vol. 
  39, 
  1905, 
  pp. 
  176-191. 
  

  

  7 
  Leisewitz, 
  W., 
  Ein 
  Beitrag 
  zur 
  Kenntnis 
  der 
  bilateralen 
  Asymmetrie 
  des 
  Saugetierschadeis, 
  Sitzungs 
  

   berichten 
  der 
  Qesells. 
  fiir 
  Morph. 
  tind 
  Phys. 
  in 
  Miinchen, 
  1906, 
  pp, 
  1-15, 
  

  

  