﻿354 
  

  

  H. 
  G. 
  SEELET 
  ON 
  NETJSTICOSATJETJS 
  PTJSILLTTS. 
  

  

  such 
  as 
  are 
  found 
  in 
  the 
  anterior 
  part 
  of 
  the 
  neck 
  in 
  Plesiosaurus 
  ; 
  

   but 
  after 
  the 
  17th, 
  where 
  the 
  vertebras 
  became 
  wider, 
  ribs 
  are 
  

   preserved. 
  Each 
  vertebra 
  is 
  about 
  3 
  mm. 
  long. 
  The 
  rib 
  is 
  about 
  

   5 
  or 
  6 
  mm. 
  long, 
  and 
  tapers 
  to 
  a 
  point. 
  It 
  is 
  impossible 
  to 
  adopt 
  

   the 
  same 
  mode 
  of 
  classifying 
  the 
  regions 
  of 
  the 
  vertebral 
  column 
  as 
  

   is 
  in 
  use 
  with 
  Plesiosaurs 
  ; 
  for 
  although 
  the 
  first 
  four 
  or 
  five 
  verte- 
  

   brae 
  with 
  ribs 
  probably 
  have 
  the 
  stout 
  expanded 
  head 
  of 
  the 
  rib 
  

   supported 
  partly 
  on 
  the 
  centrum 
  and 
  partly 
  on 
  the 
  neural 
  arch, 
  

   there 
  is 
  no 
  evidence 
  that 
  this 
  is 
  the 
  case 
  ; 
  and 
  therefore, 
  though 
  I 
  

   should 
  be 
  disposed 
  to 
  regard 
  these 
  vertebrae 
  as 
  pectoral, 
  other 
  

   writers 
  might 
  group 
  them 
  with 
  the 
  neck, 
  because 
  they 
  are 
  anterior 
  

   to 
  the 
  scapular 
  region, 
  or 
  with 
  the 
  back, 
  because 
  they 
  bear 
  ribs. 
  

  

  The 
  cervical 
  vertebrae 
  do 
  not 
  lie 
  quite 
  undisturbed 
  ; 
  the 
  atlas 
  and 
  

   axis 
  appear 
  to 
  be 
  broken 
  ; 
  the 
  third 
  vertebra 
  exposes 
  the 
  articular 
  

   end, 
  showing 
  the 
  neural 
  canal 
  to 
  be 
  higher 
  than 
  wide, 
  with 
  the 
  

   posterior 
  articular 
  face 
  of 
  the 
  centrum 
  flattened, 
  but 
  slightly 
  convex 
  

   from 
  above 
  downward. 
  The 
  upper 
  table 
  of 
  the 
  neural 
  arch 
  extends 
  

   back 
  a 
  little 
  beyond 
  the 
  neurapophyses, 
  and 
  extends 
  outward 
  a 
  little 
  

   beyond 
  them. 
  The 
  sixth 
  vertebra, 
  which 
  lies 
  on 
  its 
  side, 
  has 
  a 
  

   distinct 
  tubercle 
  for 
  the 
  rib, 
  on 
  the 
  lower 
  part 
  of 
  the 
  centrum 
  ; 
  and 
  

   the 
  fifth 
  shows 
  a 
  median 
  ridge 
  on 
  the 
  base 
  of 
  the 
  centrum, 
  with 
  a 
  

   groove 
  on 
  each 
  side 
  of 
  it. 
  The 
  middle 
  cervical 
  vertebrae 
  have 
  -lost 
  their 
  

   neural 
  arches, 
  and 
  there 
  only 
  remain 
  the 
  facets 
  to 
  which 
  arches 
  were 
  

   attached. 
  These 
  facets 
  are 
  ovate, 
  placed 
  towards 
  the 
  anterior 
  part 
  

   of 
  the 
  centrum, 
  and 
  separated 
  from 
  each 
  other 
  by 
  a 
  considerable 
  

   interval, 
  so 
  that 
  the 
  spinal 
  cord 
  rested 
  upon 
  the 
  centrum. 
  The 
  neural 
  

   arches 
  are 
  better 
  Been 
  in 
  the 
  second 
  specimen 
  (PI. 
  XIII. 
  fig. 
  3), 
  in 
  which, 
  

   however, 
  only 
  seven 
  cervical 
  and 
  three 
  or 
  four 
  pectoral 
  vertebrae 
  appear 
  

   to 
  be 
  indicated 
  with 
  certainty. 
  Only 
  the 
  dorsal 
  aspect 
  of 
  the 
  neural 
  

   arch 
  is 
  there 
  shown. 
  It 
  is 
  remarkable 
  in 
  character, 
  because 
  there 
  

   is 
  no 
  neural 
  spine, 
  the 
  neural 
  spine 
  being 
  only 
  represented 
  by 
  a 
  

   slight 
  ridge, 
  unless, 
  indeed, 
  it 
  should 
  have 
  been 
  broken 
  away 
  in 
  

   excavating 
  the 
  specimen, 
  of 
  which 
  I 
  am 
  unable 
  to 
  detect 
  any 
  certain 
  

   evidence 
  under 
  the 
  magnifying-glass. 
  This 
  slight 
  ridge 
  is, 
  moreover, 
  

   prolonged 
  forward 
  as 
  a 
  blunt 
  conical 
  spine, 
  which 
  overlaps 
  and 
  

   apparently 
  articulates 
  with 
  the 
  neural 
  arch 
  of 
  the 
  vertebra 
  in 
  front. 
  

   On 
  each 
  side 
  of 
  this 
  ridge 
  the 
  upper 
  surface 
  of 
  the 
  neural 
  arch 
  is 
  

   rounded, 
  somewhat 
  oblique, 
  and 
  forms 
  remarkable 
  zygapophyses, 
  

   the 
  zygapophysial 
  facets 
  being 
  unusually 
  large 
  both 
  in 
  front 
  and 
  

   behind. 
  In 
  front 
  they 
  are 
  completely 
  divided 
  by 
  the 
  median 
  ridge 
  ; 
  

   they 
  are 
  directed 
  horizontally, 
  and 
  form 
  an 
  unusually 
  compact 
  

   connexion 
  in 
  the 
  neck. 
  

  

  In 
  the 
  principal 
  slab 
  (PL 
  XIII. 
  fig. 
  1) 
  the 
  dorsal 
  vertebrae 
  all 
  lie 
  on 
  

   their 
  sides. 
  In 
  the 
  lower 
  part 
  of 
  the 
  dorsal 
  region 
  they 
  are 
  covered 
  by 
  

   the 
  thin 
  bones 
  of 
  the 
  pelvic 
  girdle, 
  so 
  that 
  it 
  is 
  difficult 
  to 
  count 
  the 
  

   exact 
  number. 
  Including 
  the 
  pectoral 
  vertebrae, 
  there 
  are, 
  however, 
  

   29 
  vertebrae 
  in 
  the 
  back, 
  reckoning 
  the 
  last 
  dorsal 
  to 
  be 
  in 
  a 
  line 
  with 
  

   the 
  ischio-pubic 
  suture. 
  

  

  The 
  second 
  specimen, 
  however, 
  cannot 
  count 
  more 
  than 
  26 
  ver- 
  

   tebrae 
  in 
  the 
  same 
  limits; 
  there 
  is 
  therefore 
  some 
  reason 
  for 
  

  

  