OCR Text |
Show 1875.] PLANTAR TENDONS IN BIRDS. 347 special characters of that muscle only, it being distributed to three toes, whilst the flexor perforans digitorum only supplies one. The birds with scansorial feet thus fall into two divisions, according to the arrangement of their plantar tendons, these being normal in the Psittaci and Cuculida, whilst they are extremely peculiar in the Picida, Ramphastida, Capitonida, and Galbulida. In m y paper on the Classification of Birds*, the presence or absence of the ambiens muscle made me feel justified in placing the Psittaci and Cuculida among my H O M A L O G O N A M , at the same time that the Pici, Ramphastida, Capitonida and Galbulida are arranged among the A N O M A L O G O N A T J E . These new observations are therefore strongly in favour of the naturalness of the classification proposed. There is only one other point to be considered on the present occasion, as far as this question is concerned. It is the distribution of these tendons in birds which do not possess the hallux, or in which Fig. 9. A typical Passerine Foot. there is no long flexor tendon to that digit when it is present. In all these cases both the flexor longus hallucis and the flexor perforans digitorum muscles are present and well developed, only they blend completely opposite the upper part of the tarso-metatarse to form a single common tendon to be distributed, on its splitting up, to the anterior toes-to the two of Struthio, the three of Rhea, Otis, * P. Z. S. 1873, p. 626, and 1874, p. Ill et seq. |