300 
PEOE.  T.  E.  JONES  ON  PAL2EOZOIC  OSTEACODA  [Aug.  1893* 
These  may  be  said  to  be  varieties  of  an  elongate  P.  mundula ,  with 
a  thickened  lip  of  the  sulcus  being  developed  into  a  lobe,  as  (among 
others)  in  P.  bursa,1  Krause,  and  P.  Schmidtii ,2  K.,  P.  cincinnatiensis 3 4 
(S.’A.  Miller),  and  others. 
We  see  this  feature  in  varying  conditions  among  specimens  of  P. 
mundula i  passing  into  some  forms  of  Beyricliia  Kloedeni.5 6  A  similar 
observation  has  been  made  by  Mr.  E.  0.  Ulrich,  op.  cit.  p.  136,  and 
particularly  at  p.  132,  where  he  describes  an  adult  specimen  of  Pri- 
mitia  cincinnatiensis  (pi.  x.  fig.  5),  as  having  acquired,  by  a  modifica¬ 
tion  of  the  anterior  edge  of  the  sulcus,  a  nearly  isolated  median  lobe, 
like  that  of  Klcedenia  and  Beyricliia ;  while  in  the  more  common  and 
average  forms  of  the  species  (fig.  6)  the  two  sides  of  the  sulcus  are 
merely  thickened  to  an  equal  or  nearly  equal  extent,  as  in  Ulrich’s 
Prirnitia  par allela?  P.  lativia ,7  andP.  impressa,8 9  Barrande’s  Prirnitia 
prunella and  others. 
In  PI.  XIII.  figs.  12, 13,  14  (left-hand  valves),  and  15  (a  right- 
hand  valve)  the  thickening  of  the  front  edge  of  the  sulcus  becomes 
gradually  almost  circumscribed  by  a  sloping  furrow,  first  curving 
under,  and  then  round  in  front  of  the  lobule ;  so  that,  except  in  size 
and  proportional  length,  these  specimens  very  nearly  approach 
figs.  4  and  8  of  pi.  xvii.  (1889)  referred  to  above  (. Beyricliia 
Kloedeni ,  var.  acadica)  ;  but  they  do  not  entirely  put  on  the  features 
of  Beyricliia  with  its  definite  median  lobe.  They  may  be  looked  upon 
as  Prirnitia  mundula,  var.  Kloecleniana ,  narrow  sub-oblong,  with  the 
ends  almost  equally  rounded,  though  often  modified  by  pressure. 
Pig.  14  is  much  like  Ulrich’s  fig.  5  of  P.  cincinnatiensis  (adult) ;  but 
the  lobe  is  not  sufficiently  pronounced,  and  the  valve  is  proportionally 
long  and  narrow. 
The  specimen  referred  to  Beyricliia  impendens ,  Jones,  Monogr. 
Girvan  Eoss.  1880,  p.  219,  pi.  xv.  fig.  10  c,  is  evidently  to  be 
associated  with  the  figs.  12-15  of  PI.  XIII. ;  figs.  10  a  and  b  are 
distinct. 
Eig.  12  is  in  no.  117,  hard  greenish-grey  shale  ;  fig.  13  in  no.  122  • 
fig.  14  in  no.  120  ;  and  fig.  15  in  no.  116,  all  three  being  grey  shale. 
7.  Peimitia  Uleichiana,  sp.  nov.  (PI.  XIV.  fig.  1.) 
Size. — Length  *84,  height  *64  millim. 
This  extreme  form  of  Prirnitia  has  a  wide  and  deep  sulcus  curving 
obliquely,  from  the  middle  third  of  the  dorsal  region,  downward  and 
1  Zeitschr.  Deutsch.  geol.  Gesellsch.  vol.  xli.  1889,  p.  9,  pi.  i.  figs.  7-10. 
2  Ibid.  p.  10,  pi.  i.  figs.  14,  15. 
3  As  given  by  E.  O.  Ulrich,  Jo'urn.  Cincinn.  Soc.  Nat.  Hist.  vol.  xiii.  pt.  i. 
1890,  p.  132,  pi.  x.  figs.  5,  6. 
4  Ann.  Mag.  Nat.  Hist.  ser.  6,  vol.  iii.  1889,  p.  375,  etc.,  pi.  xvi. 
5  Ibid.  pi.  xvii. 
6  Geol.  Surv.  Canada,  ‘  Contributions  etc./  part  ii.  1889,  p.  51,  pi.  ix.  fig.  7 
(referred  with  doubt  to  Prirnitia  or  Beyi'ichia). 
7  Ibid.  p.  50,  pi.  ix.  fig.  8  (differing  from  P.  parallela  in  its  proportions). 
8  Journ.  Cincinn.  Soc.  Nat.  Hist.  vol.  xiii.  pt.  i.  1890,  p.  131,  pi.  x.  figs.  3&  4. 
9  ‘  Syst.  Sil.  Bohenie/  vol.  i.  suppL  1872,  p.  550,  pi.  xxvi.  fig.  6. 
