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Show 1867.] PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 467 c. The second, third, and fourth toes turned forwards ; the first backwards. Alcedinidce. Meropidee. Bucerotidee. Momotidee. Upupidce. Coracidce. d. The first and second toes permanently turned backwards ; the third and fourth forwards. Trogonidce. This group, as I have already intimated, appears to occupy the centre of the Desmognathous division-the Musophagidee approaching the Aetomorphae, the Trogonidce the Cypselomorphae, and the Alcedinidce the Pelargomorphae. It appears to me not improbable that it may hereafter be desirable to divide this group into four, retaining the title of Coccygomorphae for the second. The CELEOMORPH^E. The rostrum is straight and usually elongated, and there are no basipterygoid processes. The maxillo-palatines are short lamellae, which, when longest, do not extend beyond the outer edges of the palatines, and are sometimes altogether rudimentary. The vomers are very delicate rod-like bones, which in some cases, at any rate, remain permanently separate. The quadrate bone is remarkably short. The sternum has two notches on each side, posteriorly, and a forked manubrial process. The carina extends to the summit of this process, its anterior edge being little (or not at all) excavated. The clavicles have no median process ; but their scapular ends are expanded, as in the typical passerine birds. The scapula accessoria has the same form as in the latter. The upper and posterior process of the tarso-metatarsus is traversed by a number of canals (five in Picus) for the flexor tendons ; and the outer distal head of the bone is divided into two parts, the fourth toe, which is articulated with it, being turned backwards. In the second, third, and fourth toes the basal phalanx is shorter than the penultimate. The tongue is long, slender, and protrusible ; and there is only one carotid. The oil-gland is surmounted by a circlet of feathers. In this group I comprehend only the Picidee and Yungidce. It is very difficult to assign the Celeomorphae to their proper place. Ordinarily they are associated together with the Psittaco-morphae and Coccygomorphae in the ' order' Scansores; but several ornithologists have pointed out the thoroughly unnatural character of this assemblage; and it is more than thirty years since |