266 THE DOCTRINE OF DESCENT. 
the discoveries, scanty as they are, of fossil intermediate 
forms. The pelvis and leg of the Ornithoscelide have 
: already been discussed. But in the 
slates of Solnhofen we have more- 
over become acquainted with the 
Archzopteryx, a bird -unfortu- 
nately mutilated and in many 
ways damaged by pressure (Fig. 
25, impression of the tail of the 
Archzopteryx Macrurus, Ow), but 
exhibiting a very valuable and 
interesting intermediate stage be- 
fj tween the tail of a reptile anda 
| bird. Among existing. birds, the 
Nandu, or American ostrich (Rhea), 
alone possesses numerous separate 
caudal vertebra ; but the’ tail of 
this bird projects so little, that it 
in no way recalls the tail of a lizard. 
Now the Archzopteryx exhibits a 
oO long. tail, bordered by two rows 
Be 25s of stiff feathers, of which the 
impression remains in extraordinary preservation. The 
skull of this valuable specimen, now in the British 
Museum, is so much injured, that no idea_can be framed 
of its construction. It is impossible to decide whether 
the jaws bore teeth. The éxample of the tortoises 
shows that within the reptile type the formation of teeth 
was replaced by horny sheaths, without a correlated 
development of the power of flight; the Pterodactyles, 
on the other hand, combine with the power of flight a 
light head, provided nevertheless with numerous teeth. 
