1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS. 187 
5. Directly Desmognathous—In the majority of Families. 
6. Doubly Desmognathous—Podargus, Steatornis, Bucerotidee 
(part). 
Of course the first three are varieties of the Schizognathous type, 
as the last three are of the Desmognathous. 
The basipterygoids vary from complete abortion in the adult, 
almost total suppression (in the Swift), to a very high state of deve- 
lopment, almost Struthious, in Steatornis. They are large and far 
forwards in the Trochilide, and large in the middle region in the 
Trogonide. 
The endoskeletal post-palatine rudiment is just dying out in 
the Caprimulgida, and it is in Caprimulgus europeus that I have 
found the greatest approach to Myithognathism; the large vomer 
is formed from a pair of centres, but it is only united to the nasal 
floor by ligament ; in the Swift the Agithognathism and the post- 
palatines are seen. 
The sternum takes on almost every possible modification in the 
Coccygomorphe ; it may have an entire hind margin, as in the 
Trochilidze and Cypselide, or one or two pairs of notches. 
The interclavicle is almost as large as in the average Passerines, 
or even in the Gallinacee, in Piaya cayana, Geococcyx affnis, 
Coceyzus americanus, and Cuculus canorus ; it is present but small 
in Saurothera vieilloti; all these are true Cuculide. 
In the Picidee and Alcedinide and others the interclavicle is 
suppressed ; in the Toucan, some of the Hornbills (e. g. B. albiros- 
tris), and in Corythaizx the rami do not unite; they do in many of the 
Psittacidee, but the ¢op, only, of each ‘“ramus*’ remains in some 
forms ; the top of the ramus is double, as in the Passerines, in Picus, 
Rhamphastos, and Alcedo. 
The syrinz is extremely variable in this group, from its lowest 
form in the Swift to a very high, but not the highest, in the Parrot. 
In some of the Cuculidz the trachea is double a long way up, quite 
like what is found in the Chelonia (see Beddard, P. Z.S. 1885, 
pp. 168-187). 
Nevertheless all these varying forms are, in some unknown way, 
related, and related most intimately. You cannot cut up the group 
without violence ; at their upper margin they interdigitate with the 
great Passerine suborder; any supposed near relationship of the 
Coccygomorphe to any other type is, I believe, an illusion ; they 
show in some cases a resemblance to the Owls, and in others, as in the 
Musophagide, to that most abortive and aberrant Curassow, the 
Hoatzin (Opisthocomus) ; but I feel certain that in these cases there 
is no true genetic affinity, it is merely adaptational isomorphism ; 
or, in plain English, similar modification, in different types of birds, 
to the same kind of life. 
The peculiarities of structure in Steatornis that are of most interest 
are those that are shared by it with ancient and extinct Reptilian 
types. Of course I do not forget that the whole of its organism is 
in a certain sense Reptilian; but although the bird grows up from 
