﻿AND 
  REPTILIA 
  OP 
  NORTH 
  AMERICA. 
  17 
  

  

  axial 
  and 
  two 
  haemal 
  elements 
  which 
  exi-st 
  as 
  supports 
  of 
  the 
  posterior 
  two 
  inferior 
  

   brachihyals 
  in 
  the 
  fishes. 
  In 
  the 
  branehiferous 
  Necturus 
  maculatus 
  a 
  considerable 
  

   modification 
  ensues. 
  The 
  four 
  superior 
  branchihyals 
  are 
  present, 
  but 
  according 
  to 
  

   Fischer, 
  the 
  first 
  and 
  second 
  haemal 
  elements 
  are 
  confluent. 
  A 
  third 
  inferior 
  branchi- 
  

   hyal 
  is 
  added. 
  If 
  we 
  now 
  turn 
  to 
  the 
  air-breather 
  Protono]»$is 
  horrida, 
  we 
  observe 
  

   a 
  marked 
  peculiarity. 
  The 
  third 
  haemal 
  branchihyal 
  remains, 
  while 
  the 
  second 
  is 
  

   confluent 
  with 
  the 
  corresponding 
  superior 
  element, 
  and 
  the 
  first 
  is 
  similarly 
  confluent 
  

   or, 
  as 
  Fischer 
  interprets 
  it, 
  the 
  first 
  branchiyal 
  of 
  the 
  superior 
  series 
  extends 
  to 
  the 
  

   axialhyal. 
  In 
  Murcenopsis 
  (Amjjhiuma), 
  a 
  greater 
  divergence 
  from 
  the 
  archetype 
  

   exists. 
  With 
  all 
  the 
  peculiarities 
  of 
  Protonopsis 
  it 
  further 
  almost 
  loses 
  the 
  second 
  

   haemal 
  element, 
  which 
  appears 
  at 
  maturity 
  as 
  a 
  process 
  on 
  the 
  first 
  pleural 
  element. 
  

  

  These 
  characters 
  may 
  be 
  tubulated 
  as 
  follows 
  : 
  

  

  A 
  Third 
  haemal 
  branchihyal 
  present. 
  

  

  a 
  First 
  and 
  second 
  haemal 
  branchihyals 
  free 
  and 
  distinct. 
  

  

  COCYTINUS. 
  

  

  aa 
  First 
  and 
  second 
  haemals 
  separate 
  from 
  each 
  other 
  but 
  confluent 
  with 
  their 
  

   pleural 
  elements. 
  

  

  PROTONOPSIS. 
  

   AMPBIUMA. 
  

  

  am 
  First 
  and 
  second 
  distinct 
  from 
  pleurals, 
  but 
  united 
  with 
  each 
  other. 
  

  

  NECTURUS. 
  

  

  A 
  A 
  Third 
  haemal 
  element 
  wanting. 
  

  

  x 
  Second 
  haemal 
  element 
  reaching 
  the 
  axis. 
  

  

  SIREN. 
  

  

  AMBLYSTOMA. 
  

  

  Larvae, 
  ■{ 
  triton. 
  

  

  Second 
  haemal 
  element 
  reduced, 
  not 
  reaching 
  axis. 
  

  

  SALAMANDPA. 
  

  

  PROTEUS. 
  

  

  Now 
  it 
  has 
  been 
  pointed 
  out 
  that 
  Cocytinus 
  agrees 
  with 
  the 
  air-breathing 
  genera 
  

   in 
  the 
  larger 
  development 
  of 
  the 
  first 
  pleural 
  and 
  haemal 
  branchihyals, 
  and 
  that 
  it 
  

   agrees 
  with 
  them 
  both 
  in 
  the 
  presence 
  of 
  the 
  second 
  and 
  third 
  haemal 
  elements. 
  But 
  

   these 
  are 
  more 
  distinct 
  than 
  in 
  either 
  of 
  these 
  genera, 
  and 
  the 
  third 
  is 
  larger, 
  and 
  

   supports 
  the 
  fourth 
  as 
  well 
  as 
  its 
  own 
  pleural 
  element. 
  

  

  The 
  presence 
  of 
  the 
  maxillary 
  bone 
  furthermore 
  excludes 
  this 
  genus 
  from 
  near 
  

   affinity 
  to 
  either 
  the 
  Trachy.stomata 
  and 
  Proteida, 
  and 
  allies 
  it 
  to 
  the 
  Amphiuma 
  and 
  

  

  