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Show 1889.] MR. *W. K. PARKER ON STEATORNIS CARIPENSIS. 187 5. Directly Desmognathous-In the majority of Families. 6. Doubly Desmognathous-Podargus, Steatornis, Bucerotidae (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 development, almost Struthious, in Steatornis. They are large and far forwards in the Trochilidae, and large in the middle region in the Trogonidae. The endoskeletal post-palatine rudiment is just dying out in the Caprimulgidae, and it is in Caprimulgus europceus that I have found the greatest approach to jEgithognathism; 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 iEgithognathism and the postpalatines are seen. The sternum takes on almost every possible modification in the Coccygomorphae ; it may have an entire hind margin, as in the Trochilidae and Cypselidae, or one or two pairs of notches. The interclavicle is almost as large as in the average Passerines, or even in the Gallinaceee, in Piaya cayana, Geococcyx afiinis, Coccyzus americanus, and Cuculus canorus ; it is present but small in Saurothera vieilloti; all these are true Cuculidae. In the Picidae and Alcedinidae and others the interclavicle is suppressed ; in the Toucan, some of the Hornbills (e. g. B. albirostris), and in Corythaix the rami do not unite; they do in many of the Psittacidae, but the top, 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 syrinx 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 Cuculidae 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 Coccygomorphae 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 Musophagidae, 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 |
