350 
POPULAR SCIENCE REVIEW. 
been carefully considered by Professor Huxley, whose views 
have already appeared in the 44 Popular Science Review ” for 
1868, vol. vii. p. 237, Plates XXVII. and XXVIII., which we 
earnestly commend to the attention of readers of this article. 
The question — 44 What is a bird, and what is a reptile V ” is 
one only of the many difficult problems which zoologists are 
called upon to answer. Its solution is, however, hopeless only 
to the mind prejudiced against all innovation, and which prefers 
to erect harsh barriers, whereas Nature, who blends the colours 
of the rainbow, knows no such abrupt limits. 
If in this article we have been enabled to show not only 
that there have been feathered bipeds with teeth, but also that 
it is still possible to treat them at least as a sub-class of birds, 
our object will be achieved. 
P.jS . — Just as this article was passing to press I learn from 
Prof. Marsh that he will figure Ichthyornis in 44 Silliman’s 
American Journal ” for October next. He adds: 44 1 have re- 
examined Hesjperornis , a large diving bird nearly six feet high, 
found in the same cretaceous formation in Kansas as the Ich- 
thyornis, and I find it also has teeth in both jaws, not in sockets 
like Ichthyornis , but in grooves as in Ichthyosaurus I (Sept. 
20, 1875.) 
EXPLANATION OF PLATE CXXV. 
Fig. 1«. Head of Merganser serrcitor, drawn from a specimen in the 
British Museum.* 
Fig. 15. Skull of same, showing denticles on mandibular border.* 
Fig. 2. Skull of Odontopteryx toliapicns , Owen, from the London clay, 
Sheppey (two-thirds natural size). 
Fig. 3 a. Archceopteryx macrura , Owen ; a restoration, copied from Pro- 
fessor Owen’s “ Comparative Anatomy of Vertebrates,” vol. 
ii. p. 586. (In the original woodcut the mandibles are repre- 
sented as serrated .) 
Pig. 35. Pounded and bilaterally symmetrical body, found on the slab 
with the Archceopteryx , from the lithographic stone, Solen- 
hofen, and attributed to the cast of brain-cavity by Mr. John 
Evans, F.R.S., President Geological Society, London. 
Fig. 3c. Small jaw, with teeth, also found associated on the same slab 
with, and attributed to Archceopteryx , by the late II. von 
Meyer. 
Fig. 4. Head of gosling before hatching, clothed with long down (or 
hair P), and with the horny knob at the end of the beak, with 
which it breaks the shell when arrived at full time. (Sug- 
gestive, possibly, of further persistent embryonal characters.) 
Copied from Professor Owen’s u Comparative Anatomy,” vol. 
ii. p. 264. 
* For permission to examine and draw figs. 1 a and 1 5, I am indebted 
to the kindness of Dr. A. Giinther, F.R.S., Keeper of the Zoological Depart- 
ment, British Museum. 
