﻿OLD 
  AND 
  NEW 
  WORLD 
  MELANL\NS 
  — 
  MORRISON 
  377 
  

  

  These 
  shells 
  have 
  spiral 
  sculpture 
  more 
  or 
  less 
  prominent 
  on 
  most 
  of 
  

   of 
  the 
  whorls, 
  and 
  in 
  some 
  of 
  the 
  species 
  there 
  is 
  a 
  peculiar 
  swelling 
  

   or 
  expansion 
  of 
  the 
  body 
  whorl 
  of 
  adults. 
  The 
  female 
  reproductive 
  

   anatomy 
  and 
  embryos 
  (from 
  the 
  brood 
  pouch) 
  of 
  the 
  Central 
  American 
  

   species 
  Aylacostoma 
  ruginosum 
  (Morelet) 
  were 
  figured 
  by 
  Crosse 
  and 
  

   Fischer 
  (1892, 
  pi. 
  49, 
  fig. 
  10). 
  In 
  these 
  figures 
  the 
  brood 
  pouch 
  

   relation 
  is 
  not 
  clearly 
  jndicated; 
  it 
  was 
  not 
  fully 
  understood 
  to 
  be 
  

   a 
  separate 
  adjunct 
  to 
  the 
  primary 
  female 
  reproductive 
  system. 
  

   Hinkley 
  (1920, 
  p. 
  47) 
  also 
  has 
  recorded 
  the 
  reproduction 
  and 
  ecology 
  

   of 
  this 
  species. 
  He 
  says: 
  

  

  Their 
  trail 
  was 
  made 
  by 
  burrowing 
  instead 
  of 
  crawling 
  on 
  the 
  surface 
  as 
  with 
  

   other 
  forms. 
  They 
  burrowed 
  somewhat 
  like 
  a 
  mole, 
  and 
  often 
  the 
  little 
  mole-like 
  

   ridge 
  could 
  be 
  followed 
  quite 
  a 
  distance, 
  and 
  the 
  moUusk 
  found 
  working 
  under 
  

   cover. 
  

  

  It 
  is 
  a 
  viviparous 
  genus. 
  When 
  cleaning 
  these 
  shells 
  the 
  embryos 
  run 
  from 
  one 
  

   to 
  three 
  to 
  the 
  individual. 
  None 
  were 
  noticed 
  with 
  more 
  than 
  three. 
  

  

  Hinkley's 
  observations 
  on 
  the 
  embryos 
  are 
  corroborated 
  by 
  dried 
  

   animals, 
  received 
  with 
  the 
  shells 
  (USNM 
  218018) 
  from 
  Hinldey, 
  

   which 
  show 
  two 
  large 
  young 
  in 
  situ 
  in 
  the 
  brood 
  pouch. 
  These 
  

   specimens 
  are 
  from 
  Lake 
  Ysabal, 
  Jocolo, 
  Guatemala. 
  

  

  Subgenus 
  Longiverena 
  Pilsbry 
  and 
  Olsson, 
  1935 
  

  

  Genotype: 
  {Aylacostoma 
  tuberculatum 
  Spix, 
  1827 
  =Melania 
  tubercu- 
  

   lata 
  Wagner, 
  1827, 
  not 
  Melania 
  tuberculata 
  (Miiller) 
  1776=) 
  Ayla- 
  

   costoma 
  (Longiverena) 
  tuberculatum 
  Spix, 
  1827, 
  by 
  subsequent 
  

   designation 
  by 
  Morrison, 
  1952. 
  

  

  This 
  subgeneric 
  group 
  of 
  Aylacostoma 
  species 
  possesses 
  prominent 
  

   longitudinal 
  sculpture 
  in 
  addition 
  to 
  the 
  spiral 
  lirae 
  present 
  on 
  the 
  

   shells 
  of 
  Aylocostoma, 
  sensu 
  stricto. 
  In 
  this 
  way, 
  the 
  upper 
  spire 
  

   whorls 
  may 
  greatly 
  resemble 
  the 
  corresponding 
  portion 
  of 
  the 
  shell 
  

   of 
  some 
  species 
  of 
  Doryssa 
  described 
  from 
  the 
  same 
  general 
  region. 
  

   More 
  study 
  is 
  required 
  for 
  proof, 
  but 
  this 
  general 
  resemblance 
  of 
  

   Doryssa 
  and 
  Longiverena 
  shells 
  may 
  be 
  another 
  outstanding 
  example 
  

   of 
  concurrent 
  and 
  convergent 
  evolution 
  of 
  the 
  famiUes 
  Pleuroceridae 
  

   and 
  Thiaridae. 
  

  

  Pilsbry 
  and 
  Olsson 
  (1935, 
  p. 
  11) 
  did 
  not 
  formally 
  designate 
  any 
  of 
  

   the 
  originally 
  included 
  species, 
  recent 
  or 
  fossil, 
  as 
  genotype, 
  so 
  we 
  

   designated 
  the 
  living 
  species 
  tuberculatum 
  in 
  order 
  that 
  the 
  animal 
  

   characters 
  of 
  the 
  group 
  may 
  be 
  used 
  to 
  correctly 
  place 
  this 
  unit 
  in 
  

   the 
  total 
  biological 
  picture. 
  

  

  Subgenus 
  Verena 
  H. 
  and 
  A. 
  Adams, 
  1854 
  

  

  ii£ 
  Genotype: 
  (Melania 
  crenocarina 
  Moricand=) 
  Aylacostoma 
  (Verena) 
  

   crenocarina 
  (Moricand). 
  

  

  