184 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, 
are only present in birds that have arrived at the highest state of 
ornithic modification and perfection. 
In the self-same skull we have then, as I have shown, a basis 
cranii with large backwardly placed “ basi-pterygoids”’ that are 
nearly Struthious ; the only carinate bird that is a rival to Steatornis 
in this respect is Pallas’s Sand-Grouse (Syrrhaptes paradoxus) (see 
Trans. Zool. Soc. vol. v. pl. xxxvi.). 
On the other hand, the ‘‘ethmo-nasal wall” has been com- 
pletely broken through and thus a complete hinge of the face on the 
skull has been formed exactly as in the Parrots, where the mobility 
of the upper face is at its greatest possible perfection. But the 
basis cranii of the Parrots, in harmony with the “ palato-quadrate ” 
arcade, is in the highest state of modification; no bird is so far from 
the old quasi-reptilian Ratite in this respect as the Parrot. 
Yet, as a set-off against this, whilst the Archaic Ratite have all 
their pre-sacral vertebree in the highest ornithie perfection, namely, 
cylindroidal, in the Parrots the dorsals are opisthoccelian ; so they are 
as we have seen in Steatornis, which also has the rare condition, as 
in Hesperornis and the Grebes, of perfect rib-bars on the axis’. 
In Wading and Water Birds this state of things is common, e.g. 
in the Penguins, Alcine Divers’, Gulls, and Limicole ; but the Psit- 
tacidze and Steatornis are the only high-class arboreal birds in which 
I have found this character of opisthoccelous dorsals. 
Here I may remark upon a most puzzling fact with regard to both 
old and new kinds of birds, namely, a prolepsis, or anticipation, so 
to speak, of Mammalian characters, in certain birds—a similarity or 
isomorphism rather, for here ‘‘ genetic affinity” has no place. 
The more Archaic the type of any one of the existing Ratite, the 
more complex is the nasal labyrinth, quite similar in its complex 
“outgrowths” to what we seein amammal. The very dorsal 
vertebra that are ancient or opisthoccelian in a Parrot, are also 
like the vertebrae of a Mammal—they -have thin terminal epiphyses. 
In by far the noblest of all birds, the Crows and Songsters, the 
form of palate which gives them their morphological name, “ Aigi- 
thognathe,” is quite similar to what is seen in the Marsupials and 
low Insectivorous Mammals. 
In this very bird, Steatornis—as in Podargus, the larger Bucerotide, 
and in certain Ducks and Swans—there is a degree of double Desmo- 
gnathism quite similar to that which exists in the Marsupialia. 
Hence we had better, at present, speak of these things as cases of 
isomorphism, or similarity—confessing our ignorance of their 
meaning—than rashly to set them down to genetic relationship. 
By taking this character or that, and closing the eyes to the other 
characters seen in Steatornis, we might find many a relation for it : 
it is, nevertheless, a friendless bird, I cannot find a near relation 
for it. And this is the more evident if we consider that the forms 
that apparently come nearest to it are Eastern and Australian types, 
1 In typical Chenomorphe—Geese, Swan, Ducks—the atlas, also, has its 
rib-bar complete, and a separately ossified rib. 
2 Not in the Loons and Grebes, 
