﻿488 
  mocEEDJxas 
  or 
  the 
  nattoxal 
  mcseim. 
  voi.xx 
  

  

  which 
  it 
  was 
  found 
  is 
  properly 
  a 
  tributary 
  of 
  the 
  Eio 
  Virgen, 
  though 
  

   now 
  lost 
  in 
  the 
  desert 
  sands 
  before 
  reaching 
  that 
  stream. 
  C. 
  macula- 
  

   rliis 
  is 
  known 
  from 
  the 
  Coh)i'ado 
  llivei', 
  and 
  also 
  from 
  springs 
  in 
  the 
  

   great 
  Colorado 
  Desert. 
  iSo 
  iar 
  as 
  Icnown 
  to 
  ns, 
  it 
  occurs 
  only 
  where 
  tlie 
  

   natural 
  drainage 
  is 
  toward 
  the 
  Colorado 
  River. 
  Of 
  the 
  remaining 
  live 
  

   species, 
  three 
  are 
  of 
  very 
  wide 
  distribution, 
  seemingly 
  able 
  to 
  set 
  at 
  

   defiance 
  what 
  are 
  effective 
  barriers 
  to 
  the 
  dispersion 
  of 
  other 
  fishes. 
  

   By 
  virtue 
  of 
  what 
  special 
  characteristics 
  they 
  accomplish 
  this 
  result 
  

   we 
  do 
  not 
  know. 
  Their 
  testimony 
  must 
  for 
  the 
  present 
  be 
  simply 
  

   ignored 
  in 
  any 
  discussion 
  of 
  faunal 
  relations. 
  The 
  case 
  is 
  different 
  

   with 
  one 
  of 
  the 
  remaining 
  species, 
  Lenciscus 
  lineatits, 
  which 
  is 
  common 
  

   to 
  mountain 
  tributaries 
  of 
  the 
  Colorado 
  and 
  to 
  the 
  Utah 
  Basin. 
  Its 
  

   occurrence 
  in 
  the 
  Colorado 
  is 
  an 
  unexplained 
  anomaly, 
  and 
  contradicts 
  

   all 
  the 
  other 
  facts, 
  which 
  bespeak 
  a 
  very 
  long 
  period 
  of 
  absolute 
  isolation 
  

   for 
  the 
  Colorado 
  Basin 
  and 
  its 
  fauna. 
  The 
  last 
  of 
  the 
  list, 
  Agosia 
  chryso- 
  

   gasler, 
  was 
  described 
  from 
  the 
  Rio 
  Santa 
  Cruz, 
  Sonora, 
  INIexico, 
  a 
  tril)u- 
  

   tary 
  of 
  the 
  Gila. 
  In 
  a 
  recent 
  paper 
  on 
  the 
  fresh-water 
  fishes 
  of 
  Sonora 
  

   by 
  Rutter 
  ' 
  it 
  is 
  listed, 
  together 
  with 
  PoeciUa 
  occidentalism 
  from 
  the 
  Rio 
  

   Sonora 
  and 
  the 
  Yaqui, 
  which 
  flow 
  independently 
  into 
  the 
  (xulf 
  of 
  Cali- 
  

   fornia. 
  These 
  Gulf 
  streams 
  are 
  practicallj^ 
  unexplored, 
  and 
  may 
  or 
  may 
  

   not 
  prove 
  to 
  have 
  had 
  a 
  comparatively 
  recent 
  connection 
  with 
  the 
  Lower 
  

   Colorado. 
  

  

  For 
  the 
  sake 
  of 
  completeness 
  we 
  include 
  in 
  this 
  paper 
  two 
  undescribed 
  

   species 
  of 
  marine 
  fishes 
  taken 
  at 
  the 
  mouth 
  of 
  the 
  Colorado. 
  Gillich- 
  

   iln/s 
  detrusus 
  enters 
  the 
  river, 
  and 
  lives 
  in 
  salt 
  or 
  brackish 
  water. 
  Like 
  

   its 
  California 
  congener, 
  G. 
  mirahilis, 
  it 
  sustains 
  immersion 
  in 
  fresh 
  

   water 
  without 
  apparent 
  inconvenience. 
  

  

  Family 
  CATOSTOMIDJE. 
  

  

  1. 
  PANTOSTEUS 
  ARIZONiE 
  Gilbert, 
  new 
  species. 
  

   (Plate 
  XXXVI.) 
  

  

  Four 
  specimens 
  of 
  this 
  species 
  were 
  taken 
  at 
  Tempe, 
  Arizona. 
  It 
  is 
  

   readily 
  distinguished 
  from 
  all 
  other 
  species 
  of 
  Panfostcns 
  by 
  the 
  large 
  

   size 
  of 
  its 
  scales. 
  

  

  Head 
  broad 
  and 
  flat, 
  4^ 
  in 
  length. 
  Interorbital 
  space 
  flattened 
  or 
  

   very 
  slightly 
  concave, 
  2^% 
  in 
  head. 
  Depth 
  4|; 
  D. 
  11 
  or 
  12; 
  A. 
  7; 
  

   scales 
  7 
  or 
  8 
  — 
  05 
  to 
  67 
  — 
  11 
  to 
  15. 
  The 
  scales 
  are 
  unusually 
  large 
  in 
  

   front 
  of 
  dorsal 
  and 
  along 
  back, 
  much 
  smaller 
  along 
  lateral 
  line, 
  and 
  

   become 
  minute 
  on 
  belly. 
  Those 
  along 
  the 
  lateral 
  line 
  grow 
  gradu- 
  

   ally 
  larger 
  posteriorly. 
  Eye 
  moderate, 
  very 
  high 
  up, 
  posterior, 
  ^ 
  in 
  

   snout, 
  6 
  in 
  head, 
  2i 
  in 
  interorbital 
  space; 
  orbital 
  ring 
  somewhat 
  raised. 
  

   Preorbital 
  less 
  than 
  half 
  as 
  wide 
  as 
  long. 
  Snout 
  considerably 
  longer 
  

   than 
  rest 
  of 
  head. 
  Isthmus 
  very 
  broad, 
  2J 
  in 
  head. 
  Greatest 
  depth 
  

  

  'Proc. 
  Cal. 
  Aiad. 
  Sci., 
  1896, 
  p. 
  260. 
  

  

  