WHICH  HAVE  CONSOLIDATED  ON  STEEP  SLOPES. 
783 
a distinct  species  cannot  be  made  out  of  these  large  leaves,  as  they  entirely  agree  in  ner- 
vation with  the  others.  These  large  leaves  attain  a length  of  2 inches  and  a breadth 
of  1 inch,  while  the  smaller  ones  are  only  1 inch  long  by  ^ inch  broad.  The  secondary 
nerves  run  almost  parallel,  and  with  a slight  curve  to  the  border  nerve,  and  run  into  it 
at  almost  right  angles.  In  the  middle  of  the  area  they  have  a shortened  secondary 
nerve,  which  over  two-thirds  of  this  area  runs  into  a network.  The  border  nerve  is  quite 
as  strong  as  the  secondary  nerves ; but  the  middle  nerve,  or  midrib,  is  much  stronger. 
It  is  striking,  that  the  secondary  nerves  are  rather  more  distinct  than  in  the  living- 
myrtle  leaves ; and  this  is  in  like  manner  the  case  in  the  leaves  represented  in  nature- 
printing. 
Here  and  there  are  seen  fine  dots  close  together  which  appear  to  belong  to  the  leaf. 
3.  Pistacia  lentiscus,  figs.  I and  2,  Plate  LI. — Several  beautiful  pinnated  leaves.  The 
general  leaf-stalk  is  in  some  distinctly  winged,  while  in  others  it  is  hardly  to  be  observed. 
That  this  winged  border  has  not  always  been  preserved,  is  proved  by  the  circumstance 
that  it  sometimes  exists  on  one  side  and  is  wanting  on  the  other.  The  stalk  lies  below 
this  and  forms  a furrow,  whilst  the  winged  borders  stand  out  a little  or  are  placed  slant- 
ing against  the  stalk.  The  leaves  alternate,  though  for  the  most  part  nearly  approxi- 
mating ; on  each  side  four,  rarely  five,  the  end  leaves  wanting.  The  leaves  are  leathery, 
sessile,  elliptical  or  long  elliptical,  narrowed  at  the  base,  somewhat  inequilateral,  gene- 
rally the  upper  side  narrower  than  the  lower,  as  in  Pistacia  lentiscus.  From  the  midrib 
proceed  very  delicate  curved  secondary  nerves,  which  are  frequently  efiaced.  The  size 
of  the  leaves  varies  from  7 lines  in  length  and  3 lines  in  breadth,  to  as  much  as  14  lines 
in  length  and  6^  lines  in  breadth.  The  edge  of  the  leaves  generally  curled,  and  agreeing 
with  the  leaves  of  Pistacia  lentiscus., — 1st,  in  the  leathery  structure  of  the  surface  of  the 
leaf ; 2ndly,  in  the  number  and  position  of  the  leaflets ; 3rdly,  in  the  form  of  the  sessile 
leaves ; 4thly,  in  the  -winged  leaf-stalk  (in  the  living  species  the  breadth  of  the  wing-border 
is  very  variable);  5thly,  in  the  nervation;  and  Bthly,  in  the  rolled  edge  of  the  leaf. 
I think,  therefore,  I have  good  ground  for  referring  these  leaves  to  the  Mastic  tree, 
although  I was  a long  time  in  doubt  about  them. 
B. 
[List  op  Fossil  Shells  fkom  Nizzeti  neae  Aci  Gastello,  found 
BY  Peofessor  Andrea  Aeadas  (see  p.  778). 
N.B.  The  species  marked  with  an  asterisk  are  those  which  do  not  appear  in  the  list 
published  by  Philippi  in  his  '•Pnumeratio  Molluscorum  Sicilice,'  vol.  ii.  p.  262. 
The  species  printed  in  italics  are  extinct,  or  not  known  as  living. 
Mactra  triangula,  Ren.  ; common. 
*Mactra  solida,  L. ; very  rare. 
Corbula  nucleus,  Lamk.  ; very  common. 
MDCCCLVIII.  5 
^Diplodonta  apicalis,  Philip.  ; very  rare. 
Tellina  distorta,  Poli  ; very  rare. 
*Lucina  spinifera.  Montag.  ; rare. 
