PIC ASIAN BIRDS, 



369 



Passeres may be styled schizopelmous, since, being otherwise similar, they differ in 

 having the tendons quite separate ; this arrangement is illustrated in Fig. 171 A. In 

 Fig. 171C it is quite otherwise ; here is a zygodactylous foot, but it is the fl. perforans 

 which is single, only supplying the third toe, while the fl, hallucis split into three, 

 giving a branch to the second and fourth toes as well as to the first one, or the hallux ; 

 being opposed to the above, and only found in these nou-cuculine, pair-toed birds, we 

 propose to call this arrangement antiopelmous. 



While on this subject we may at once describe two other plantar arrangements, 

 which obtain among birds of the present order. The trogons are also ' pair-toed,' or 

 * yoke-toed,' that is, they have two toes in front and two behind ; but while in the 

 woodpeckers the first and fourth are directed backwards, in the trogons the first and 

 second take that position ; hence they are said to be heterodactylous. To this entirely 

 unique disposition of the toes corresponds an equally unique distribution of the ten- 

 dons, for, as shown in Fig. 171D, each of the two flexores splits up into two, the/, hal- 



-flh 



...fpd 



f P d~ 



fpd~ 



flh 



D 



FIG. 171. Diagrams showing the manner of distribution of the deep plantar tendons ; flh, flexor longus 

 hallucis ; fpd, flexor perforans digitorum ; v, vinculum. I -IV, first to fourth toes. A, noniopelmous (schizopel- 

 mous) ; B, synpelmous ; C, antiopelmous ; D, heteropelmous. 



lucis supplying first and second digits, i. e. the posterior toes, while/! perforans bends 

 the two anterior toes, the third and the fourth. This structure, found nowhere else, we 

 shall designate as heteropelmous. We have finally to consider Fig. 171B, which repre- 

 sents an arrangement to be called synpelmous, since the two tendons are completely 

 blended. It is to be remarked that the direction of the fibres seems to indicate that 

 the/, hallucis goes to the fourth toe, while the branch to the first one is supplied from 

 the other tendon, a supposition the more probable since in a slight modification of 

 this arrangement the slip to the first toe (hallux) branches off from the main stem 

 above the point where the two tendons blend together. The synpelmous distribution 

 of the deep plantar tendons obtains especially in the swifts, humming-birds, goat- 

 suckers, king-fishers, horn-bills, and their allies, many of which are also syndacty- 

 lous. We may finally state as an important fact that the synpelmous, the heteropel- 

 mous and the antiopelmous arrangements are entirely peculiar to the present order. 



Garrod thought that he had another set of characters concomitant with the pres- 

 sence or absence of the ambiens muscle, finding as he did that in all homalogonatous 

 birds the dorsal feather tract bifurcates between the shoulder, while in the anomalo- 

 VOL. iv. 24 



