334 
rely  wholly  (Siphonophora)  or  partially  (Stemmiulus)  free,  but  never 
so  distinct  as  in  the  Limacomorpha  or  Oniscomorpha  and  almost  always 
completely  indistinguishable  from  the  terga.  The  pedal  laminae  (tra- 
cheal plates)  in  the  form  of  two  unpaired  sternal  sclerites,  to  which 
the  legs  are  directly  articulated.  Some  of  the  segments  (excepting 
always  the  anterior  4  and  the  last)  are  very  generally  furnished  with 
a  pair  of  foramina  repugnatoria  ;  when  absent  these  apertures  are 
sometimes  represented  on  each  segment  by  large  isolated  setae  (Chor- 
deumoidea);  sometimes  the  whole  segment  is  covered  ■  with  hairs 
(Cryptodesmus). 
Either  one  pair  or  both  pairs  of  legs  of  the  7<*  segment  are  modi- 
fied in  the  cT  to  act  as  copulatory  organs. 
My  opinions  as  to  the  affinities  of  the  families  of  the  Helmintho- 
morpha  have  undergone  some  change  since  the  publication  of  my 
paper  upon  the  Classification  of  the  Diplopoda.  I  recognise  for  instance 
that  it  is  impossible  to  regard  the  Polyzonidae  as  degenerate  Iulidae; 
consequently  I  adopt  Brandt's  name  Colobognatha  for  a  suborder  to 
contain  the  Polyzonidae,  Siphonophoridae  etc.  The  Chordeumidae ,  too, 
have  been  removed  from  the  Iuloidea,  and  have  been  raised  to  the 
rank  of  a  suborder  by  my  friends  Messrs.  Cook  and  Collins.  There 
are  thus  4  suborders  for  the  Helminthomorpha  namely  Colobognatha, 
Chordeumoidea,  Polydesmoidea  and  Iuloidea.  Since  sending  this  paper 
to  press  in  Dec.  1893,  I  have  seen  Mr.  Bollman's  posthumous  article 
on  the  classification  of  the  Myriopoda.  Bull.  U.  S.  Nat.  Mus.  n°  46, 
p.  153  etc.  I  consider  that  Mr.  Bollman  has  done  much  to  systema- 
tise our  knowledge  of  these  difficult  animals  by  his  praiseworthy  attempt 
to  remodel  their  classification.  But  although  I  think  that  most  of  his 
innovations  are  steps  in  the  right  direction,  yet  there  are  so  many 
points  of  detail  in  which  I  can  not  agree  with  him  that  I  have  deci- 
ded to  allow  the  classification  proposed  above  to  stand  unchanged 
until  an  opportunity  occurs  of  reexamining  the  whole  question. 
Suborder  COLOBOGNATHA,  Brandt. 
Oken's  Isis,  p.  704  (1834). 
Body  elongate,  composed  of  from  about  30  to  over  70  segments 
and  capable  of  being  spirally  coiled. 
Head  generally  small  and  often  tucked  under  the  l»t  segment.  Eyes 
