﻿194 
  Mr. 
  C. 
  T. 
  Regan— 
  A 
  Synopsis 
  of 
  the 
  

  

  groove, 
  and 
  the 
  vertical 
  fins 
  are 
  confluent. 
  Tlie 
  branchial 
  

   pouches 
  communicate 
  directly 
  with 
  the 
  oesophagus. 
  

  

  Family 
  Petromyzonida?. 
  

  

  Characters 
  included 
  in 
  the 
  ordinal 
  diagnosis. 
  

  

  Coasts 
  and 
  rivers 
  of 
  temperate 
  regions, 
  most 
  or 
  all 
  

   spawning 
  in 
  fresh 
  water. 
  

  

  The 
  specimens 
  enumerated 
  are 
  those 
  in 
  the 
  British 
  Museum 
  

   collection. 
  

  

  Synopsis 
  of 
  the 
  Genera. 
  

  

  I. 
  Two 
  tricuspid 
  supraoral 
  lamina? 
  1. 
  Mordacia. 
  

  

  II. 
  A 
  single 
  supraoral 
  lamina. 
  

  

  A. 
  Anterior 
  lingual 
  lamina 
  bi- 
  or 
  tricuspid 
  ; 
  supraoral 
  lamina 
  broad, 
  

  

  quadricuspid 
  2. 
  Qeotria. 
  

  

  B. 
  Anterior 
  lingual 
  lamina 
  with 
  two 
  curved 
  denticulated 
  ridges 
  

  

  separated 
  by 
  a 
  median 
  longitudinal 
  groove 
  ; 
  supraoral 
  lamina 
  

   narrow, 
  bicuspid 
  3. 
  Petromyzon. 
  

  

  C. 
  Anterior 
  lingual 
  lamina 
  with 
  a 
  single 
  transverse 
  denticulated 
  

  

  ridge. 
  

  

  1. 
  Supraoral 
  lamina 
  narrow. 
  

  

  Supraoral 
  lamina 
  bi- 
  or 
  tricuspid 
  ; 
  dorsal 
  fins 
  united. 
  4. 
  IcJithyomyzon. 
  

   Supraoral 
  lamina 
  unicuspid 
  ; 
  dorsal 
  fins 
  separate 
  . 
  . 
  5. 
  Caspiomyzon. 
  

  

  2. 
  Supraoral 
  lamina 
  broad, 
  bi- 
  or 
  tricuspid. 
  

  

  a. 
  Disc 
  covered 
  with 
  numerous 
  teeth, 
  radially 
  arranged. 
  

  

  6. 
  Eudontomyzon. 
  

  

  b. 
  Disc 
  with 
  a 
  marginal 
  series 
  of 
  small 
  teeth, 
  an 
  anterior 
  group 
  

  

  of 
  teeth, 
  and 
  3 
  or 
  4 
  enlarged 
  teeth 
  on 
  each 
  side 
  ; 
  no 
  radial 
  

   series 
  of 
  teeth. 
  

   Last 
  pair 
  of 
  lateral 
  teeth 
  connected 
  by 
  a 
  postei-ior 
  

  

  series 
  of 
  teeth 
  parallel 
  to 
  the 
  marginal 
  series 
  . 
  . 
  7. 
  Entosphemis. 
  

   Posterior 
  part 
  of 
  disc 
  toothless, 
  except 
  for 
  the 
  

  

  marginal 
  series 
  8. 
  Lampetra. 
  

  

  1. 
  MOEDACIA. 
  

  

  Caraqola, 
  Gray, 
  Chondropt. 
  p. 
  143 
  (1851), 
  or 
  Proc. 
  Zool. 
  Soc. 
  1851, 
  

  

  p. 
  239. 
  

   Mordacia, 
  Gray, 
  t. 
  c. 
  p. 
  144, 
  and 
  I. 
  c. 
  ; 
  Giinth. 
  Cat. 
  Fish. 
  viii. 
  p. 
  507 
  

  

  (1870). 
  

  

  Disc 
  covered 
  with 
  radially 
  arranged 
  teeth. 
  Two 
  well- 
  

   separated 
  tricuspid 
  supraoral 
  lamina? 
  ; 
  infraoral 
  lamina 
  with 
  

   9 
  unequal 
  cusps. 
  Anterior 
  lingual 
  lamina 
  with 
  a 
  V-shaped 
  

   denticulated 
  ridge, 
  the 
  apex 
  of 
  the 
  V 
  directed 
  backwards, 
  the 
  

   most 
  anterior 
  denticle 
  on 
  each 
  side 
  more 
  or 
  less 
  enlarged. 
  

   Dorsal 
  fins 
  separate. 
  

  

  Australia 
  ; 
  Chile. 
  

  

  