286 
ME.  E.  LYDEKKEE  ON  THE  JAW  OF 
[Aug.  1893*. 
have  been  already  referred  to  as  distinguishing  those  of  the  specimen 
under  consideration.  It  is  true  that  Th.  antiquus  is  of  much  smaller 
size  than  the  Dinosaur  before  us  ;  hut  this  difference  does  not  apply 
to  the  tooth  originally  described  by  Riley  and  Stutchburyas  Palceo - 
saurus  platyodon ,  and  subsequently  referred  by  Prof.  Huxley  to 
Thecodontosaurus.  I  find,  however,  that  in  a  lower  jaw  of  Th. 
antiquus  figured  by  the  last-mentioned  writer1  there  is  not  the 
deflection  of  the  symphysial  extremity  which  forms  so  characteristic 
a  feature  of  the  present  specimen,  and  which  must  assuredly  be 
regarded  as  of  generic  value.  The  same  feature  is  also  wanting  in 
the  lower  jaw  of  the  nearly  allied  American  genus  Anchisaurus ,  in 
which  Prof.  Marsh  2  gives  the  number  of  lower  teeth  as  18.  Prom 
the  small  Indian  Epicampodon 3  the  present  specimen  is  sharply 
distinguished  by  the  existence  of  serrations  on  the  front,  as  well  as 
on  the  hinder  margins  of  the  teeth. 
I  take  it,  therefore,  that  while  the  Oxfordian  Dinosaur  cannot  be 
assigned  to  the  Megalosauridse,  it  appears  to  be  more  nearly  allied 
to  the  Anchisauridse,  or — as  the  family  ought  properly  to  be  called — 
Thecodontosauridse.  It  seems,  however,  to  differ  from  all  described 
genera  of  that  family  by  the  marked  deflection  of  the  mandibular 
symphysis  ;  and  on  this  ground  I  propose  to  refer  it  to  a  new  genus 
under  the  designation  of  Sarcolestes.  The  species  may  be  appro¬ 
priately  named  after  the  discoverer  of  its  type,  S.  Leedsi. 
Postsceipt. 
[During  the  discussion  on  the  above  my  attention  was  called  to 
the  maxilla  described  by  Prof.  Seeley  as  Priodontognaihus  Phillipsi , 4 
of  which  the  age  is  not  definitely  known,  although  it  is  probably 
either  Wealden  or  Jurassic.  By  the  courtesy  of  Prof.  Hughes  I 
have  had  an  opportunity  of  comparing  that  specimen  with  the  man¬ 
dible  under  consideration,  and  find  that  there  is  a  probability  of 
the  two  belonging  to  allied  forms,  although  they  are  certainly 
specifically  distinct.  In  both,  the  successional  teeth  pierce  the  bone 
on  one  side  of  those  in  use  :  the  new  alveoli  in  the  upper  jaw 
being  situated  externally  to  those  of  the  teeth  in  use,  while  in  the 
mandible  they  are  internal, — such  a  reversal  being  exactly  what 
we  might  expect  in  the  opposite  jaws  of  one  and  the  same  animal. 
Both  have  teeth  of  a  very  similar  general  type,  but  those  of  Prio- 
dontognathus  (PI.  XI.  fig.  3)  have  larger  marginal  cusps,  and  are 
altogether  more  Scelidosaurian  in  appearance.  Moreover,  there  is 
no  decisive  evidence  that  the  maxilla  of  the  latter  was  deflected 
in  a  manner  to  correspond  with  the  lower  jaw  from  Peterborough. 
"Whether,  however,  the  two  specimens  may  not  belong  to  two  species 
of  a  single  genus  I  am  not  prepared  to  say ;  and  therefore  the 
generic  name  which  I  have  suggested  above  may,  foi;  the  present  at 
least,  stand.  The  teeth  of  Priodontognaihus  are  somewhat  suggestive 
1  Quart.  Journ.  Geol.  Soc.  vol.  xxvi.  (1870)  pi.  iii.  fig.  1. 
2  Am.  Journ.  Sci.  ser.  3,  vol.  xliii.  (1892)  pi.  xv.  fig.  1. 
3  See  Lydekker,  Cat.  Foss.  Rept.  Brit.  Mus.  pt.  i.  (1888)  p.  174. 
4  Quart.  Journ.  Geol.  Soc.  vol.  xxxi.  (1875)  p.  439. 
