302 
PEOF.  T.  E.  JONES  ON  PALiEOZOIC  OSTEACODA  [Aug.  1 8935, 
when  a  series  of  individuals  show  more  or  less  clearly  both 
conditions,  as,  for  instance,  among  these  Girvan  specimens,  and  in 
Primitia  granimarginata ,l  Ulrich  (Carboniferous),  and  in  the  P. 
cincinnatiensis,  above  mentioned.  lor  conveuience,  however,  if  not 
on  biological  grounds,  the  generic  division  may  be  made  at  the 
limit  of  the  isolation  of  the  tubercle  by  the  side  of  the  sulcus; 
and,  indeed,  we  know  not  the  possible  physiological  value  of  the 
change  of  structure  in  the  soft  parts  of  the  animal,  thus  indicated 
by  modifications  of  the  outside. 
In  no.  116,  grey  shale. 
Beyrichia  parasitica ,  Hall  (Quart.  Journ.  Geol.  Soc.  vol.  xlvi. 
1890,  p.  17,  fig.  1),  presents  an  advanced  stage  in  Beyrichian 
outcome  beyond  B.  Kloedeni-infecta ;  and,  were  the  two  furrows 
more  equal  and  symmetrical,  it  would  be  near  to  Kloedenia. 
3.  Beyeichia  Klcedeni,  M‘Coy,  var.  scotica,  Jones  &  Holl,  Ann. 
Mag.  Nat.  Hist.  ser.  5,  vol.  xvii.  1886,  p.  356,  pi.  xii.  fig.  10. 
Size. — Length  '8,  height  *6  millim. 
44  This  is  relatively  shorter  than  B.  Klcedeni,  subvar.  clausa ,  J.  &  H.r 
being  more  nearly  semicircular ;  the  middle  lobe  is  rather  more 
definitely  egg-shaped,  and  there  is  a  thick,  raised,  marginal  rim  in 
all.  A  smooth  sub-variety  was  described  and  figured  as  B.  Kloecleni 
by  one  of  us  in  the  4  Monograph  of  the  Silurian  Eossils  of  the 
Girvan  District,’  by  Nicholson  and  Etheridge  Jun.,  1880,  p.  218, 
pi.  xv.  figs.  8-8  b;  and  of  the  present  strongly  granulate  form 
(fig.  10)  we  have  seen  four  imperfect  specimens  (in  Mrs.  Gray’s 
collection)  from  Bargany-Pond  Burn.  Of  these,  one  small  hollow 
cast,  preserving  the  best  proportion  of  characters,  is  here  figured  ; 
but  the  mid-lobe  is  higher  up  than  in  older  individuals.  Excepting 
this  lobe,  the  surface  bears  large  scattered  granules,  sometimes 
concentrically  arranged,  and  the  raised  margin  has  a  distinct  row 
of  them  also.  The  specimens  occur  in  a  hard  limestone,  and  have 
not  been  got  out  free  of  matrix.”  The  rock  is  of  Llandovery  age. 
4.  Beyeichia  Kl(edeni,  M‘Coy.  Other  varieties.  (PI.  XIV* 
fi-gSa  3,  4.) 
Size. — Eig.  3  :  Length  '68,  height  '44  millim. 
Eig.  4  :  Length  1*04,  height  '68  millim. 
In  PI.  XI V.  fig.  3  we  see  definite  indications  of  the  three  lobes  of 
B.  Kloecleni  in  their  normal  relation  to  each  other,  except  that  the 
anterior  (smallest)  looks  as  if  it  were  modified  in  its  growth  ;  or  it 
may  have  been  affected  bjr  accident  of  fossilization. 
Eig.  4  may  be  a  wide-margined  symmetrical  variety  of  B.  Kloedeni , 
with  indications  of  three  unequal  and  not  clearly  defined  lobes. 
When  the  margin  is  present  in  Beyrichia  it  is  usually  ornamented, 
and  rarely  so  broad  as  in  fig.  4.  B.  Klcedeni ,  however,  figured  in 
the  4  Monogr.  Girvan.  Eossils,’  1880,  pi.  xv.  figs.  8  a,  b ,  has  a 
correspondingly  broad  margin. 
1  Journ.  Cincinn.  Soc.  X.  H.  vol.  xiii.  pt.  ii.  1891,  p.  201,  pi.  xii.  fig.  8. 
