18 MARY L. WALKER ON THE FORM OF THE QUADRATE BONE IN BIRDS. 
spite of this well-formed mandibular articulation, the quadrate of Pterocles is not 
very dissimilar to the Pigeon’s. It is much more divergent from the Fowl’s, 
however, instead of being intermediate between the two. 
ODONTORNITHES. 
In commencing this study, we had from the first the hope of finding some 
evidence as to the relationship of the Odontornithes in the quadrate bone, which 
Professor Marsx figures* for the two genera Hesperormis and Ichthyornis, without 
drawing any conclusions from its characters. 
Professor ParkKER, commenting on OWEN’s account of the skull of Notoriis,+ 
says, “this knob-like [pterygoid] process on the os quadratum of the great 
Notornis is to the morphologist ‘a nail fastened in a sure place; and on it, 
supposing a mere fragment of this os quadratum had been all we possessed of this 
bird, might have been hung the whole weight of my assertion, viz., that the bird in 
question is not a congener of the Dimornis.” We should be inclined to make 
precisely the same observation regarding the quadrate of the Hesperorms and 
Ichthyornis. 
The positions in which Professor Marsu has figured his quadrates are some- 
what different from those that we have adopted; and it is far from easy to 
understand from his figures the exact shape of the bones. But we see from his 
figures of the quadrate of Hesperorms that this quadrate is a bone with a long, 
slender, well-formed shaft, a head whose two capitula are defined though not 
deeply cleft, a slender pointed (?) anterior process sprmging from the shaft at some 
distance from the head, a distinctly prominent pterygoid process, and a deep 
quadrato-jugal cup. By everyone of these characters the bone is far removed from 
the Ratite type. It seems to resemble the Grebe’s more than any other quadrate 
that we have figured, and if we rightly understand Marsn’s view of the inferior 
surface (loc. cit., Pl. ii. fig. 6c), which appears to show chiefly what we have called 
the anterior condyle, with its external trochlear surface, that region of the bone 
does not discredit the affinity that its other characters suggest. 
The quadrate of Ichthyornis appears to be less perfectly preserved. In 
Marsn’s figures (loc cit. p. 121, woodeuts) we are struck by the bulkiness of its 
lower extremity, by its exceedingly prominent pterygoid condyle, and by its minute 
quadrato-jugal cup. The anterior process is lost, but from the appearance of its 
broken base it seems to have been stout and broad. In all these characters, the 
quadrate of Ichthyornis very strikingly resembles that of the Tern. 
* Odontornithes, 4to. Washington, 1880. 
+ On the Skull of the Ostrich. Phil. Trans., Vol. 156, p. 166. 1866. 
