568  DINOSAURIAN  TEETH  FROM  AYLESBURY.  [Nov.  1893, 
distinct  channel  from  the  general  surface  of  the  crown,  while  on 
the  other  border  it  merges  gradually  into  the  same.  In  the  tooth 
of  Hoplosaurus  the  same  aspect  of  the  tooth  is  there  uniformly 
convex.  Although  their  summits  are  somewhat  worn,  it  is  now 
perfectly  evident  that  the  present  specimen  and  the  one  represented 
in  fig.  2  had  broader  and  shorter  crowns  than  the  tooth  of  Hoplo- 
saurus,  from  which  they  are  evidently  generically  distinct.  The 
broadest  diameter  of  the  Aylesbury  specimen  is  1-35  inch. 
The  second  of  the  new  specimens 
is  the  crown  of  a  much  smaller  tooth 
of  similar  character.  This  small  size 
indicates  that  it  probably  came  from 
the  hinder  extremity  of  the  jaw ; 
while  it  further  suggests  that  the 
larger  tooth  may  likewise  have  been 
somewhat  far  back  in  the  series, 
and  consequently  inferior  in  size  to 
some  of  the  others. 
Comparing  the  larger  of  the  Ayles¬ 
bury  specimens  with  the  tooth  from 
the  Portlandian  of  Boulogne  figured 
by  De  La  Moussaye  1  as  Neosoclon , 
and  identified  by  Sauvage 2  with 
his  Cauloclon  precursor ,  I  find  an 
identity  of  characters ;  the  only 
difference  being  that  the  Boulogne 
specimen  is  somewhat  the  larger,  having  a  transverse  diameter  of 
1*46  inch.  Both  may  accordingly  be  assigned  to  the  same  species. 
"With  regard  to  the  form  to  which  the  so-called  Neosodon  belongs, 
I  have  shown  3  that  the  teeth  so  described  are  probably  referable 
either  to  the  reptile  typified  by  a  humerus  from  the  Kimeridgian  of 
Weymouth,  described  as  Cetiosaurus  humerocristatus ,  or  to  a  closely 
allied  form.  Finding  that  there  are  no  characters  by  which  the 
type  of  the  species  last  named  can  be  distinguished  generically  from 
Pelorosaurus  of  the  Wealden,  I  have,  however,  assigned  it  to  that 
genus,  with  the  name  of  P.  humerocristatus ; 4  and  it  is  to  this  same 
form  that  I  would  tentatively  refer  both  the  Boulogne  and  the 
Aylesbury  teeth. 
The  other  two  teeth  of  large  Sauropodous  Dinosaurs  being  in  the 
National  Collection,  I  am  glad  to  be  able  to  announce  that  the  owner 
of  the  Aylesbury  specimens  has  generously  presented  them  to 
the  British  Museum  ;  and  it  may  be  hoped  that  in  the  course  of 
time  other  examples  of  these  teeth  will  eventually  reach  the  same 
collection,  and  enable  further  comparisons  to  be  instituted. 
1  Bull.  Soc.  Geol.  France,  ser.  3,  vol.  xiii.  (1885)  p.  51. 
2  Ibid.  vol.  xvi.  (1888)  p.  626. 
3  Cat.  Foss.  Kept.  Brit.  Mus.  pt.  iv.  (1890)  p.  241. 
4  Log.  cit. 
Fig.  4. — Inner  and  Outer 
Aspects  of  Crown  of 
Hinder  Tooth  of  Peloro¬ 
saurus  humerocristatus. 
[Natural  size.] 
