Vol.  49.]  FROM  THE  DISTRICT  OF  GHRVAN,  AYRSHIRE.  303 
Figs.  3  and  4  are  in  nos.  118  and  119,  both  of  them  hard  greenish- 
grey  shale. 
5.  Beyrichia  impar,  sp.  nov.  (PI.  XIV.  fig.  5.) 
Size. — Length  1*0,  height  *72  millim. 
This,  at  first  sight,  somewhat  obscure  fossil  may  be  seen  to 
resolve  itself  into  a  Beyriehian  form  with  a  narrow,  curved,  median 
lobe,  separated  on  one  side  by  a  widely-ovate  sulcus  from  a  curved 
lobe-like  swelling,  and  on  the  other  side  by  a  shallow  furrow  from 
a  conspicuous  round  tubercle  on  the  other  convex  moiety  of  the  valve 
(not  quite  perfect).  This  latter  might  be  the  anterior  part,  for  the 
larger  or  stronger  furrow  is  usually  behind  the  middle  ;  but  in  the 
outline  of  thisvalve  the  boldest  curve  indicates  that  it  is  the  posterior 
moiety.  There  is  a  distant  resemblance  to  be  traced  in  the  furrows, 
lobes,  and  tubercle  to  those  of  fig.  12,  pi.  xiii.  Ann.  Mag.  Nat.  Hist, 
ser.  5,  vol.  xix.  1887,  p.  406,  there  referred  with  doubt  to  Octonaria? 
jparadoxa. 
In  no.  113,  a  hard  greenish-grey  shale. 
IV.  Genus  TJlrichia,  Jones,  1890. 
Quart.  Journ.  Geol.  Soc.  vol.  xlvi.  (1890)  p.  543. 
1.  Ulrichia,  sp.  (?).  (PI.  XIV.  fig.  6.) 
Size. — Length  1*12,  height  *76  millim. 
Pig.  6,  PI.  XIV.  in  its  sub-oblong  shape,  straight  back,  nearly 
parallel  and  slightly  curved  ventral  border,  and  somewhat  equal, 
rounded  ends,  represents  a  valve  resembling  those  of  several  Primitian 
and  Beyriehian  groups  ;  but  it  exhibits  three  isolated  tubercles,  in  a 
nearly  straight  row  (the  middle  one  rather  lower  down  than  the 
others)  along  the  dorsal  moiety  of  the  valve,  and  above  the  median 
line.  The  surface  is  partially  pitted. 
Three  such  tubercles  occur  also  in  KirTcbya  tricollina,  Jones  and 
Kirkby  (Carboniferous),  with  some  difference  as  to  relative  position  ; 
and  in  Beyrichia  tricollina ,  Ulrich  (Devonian),  with  a  great  difference 
in  arrangement.  Doubtless  they  have  an  analogy  to  those  in  fig.  3. 
It  may  be  that  the  three-tubercled  Primitian  forms  should  be 
definitely  included  in  TJlrichia  (for  some  remarks  on  this  point, 
see  the  preceding  paper,  p.  293),  and  some  such  forms  have 
been  provisionally  referred  to  this  genus.  If  we  regard  these 
tubercles  as  either  survivals  or  forerunners  of  the  three  lobes  of 
Beyrichia ,  rather  than  the  modified  sulcus  of  Primitia ,  this  form 
should  be  assigned  to  a  genus  closely  allied  to  Beyrichia  ;  and 
indeed  this  latter  sometimes  has,  in  the  young  state,  an  Ulrichian 
aspect  with  two  medio-dorsal  knobs,  namely,  in  B.  nova-scotica , 
J.  &  K.,1  in  which,  when  adult,  the  three  normal  lobes  are  sufficiently 
distinct.  At  all  events  the  genera  are  closely  allied. 
Pig.  6  is  in  no.  123,  a  grey  shale. 
1  Geol.  Mag.  dec.  3,  vol.  i.  1884,  p.  358,  pi.  xii.  fig.  7;  and  Quart.  Journ. 
Geol.  Soc.  vol.  xlvi.  1890,  p.  544. 
