CONDITIONS OF THE PODOTHECA. 



47 



§ 80. When the harder sorts of either scutella or plates are roiiglienecl 

 without obvious elevation, the leg is said to be scabrous or scaricms. But 

 scabrous is also said of the under surfaces of the toes, when these develop 

 special j9acZs, or wart-like bulbs (called tylari) ; excellently shown in most 

 hawks. The softer sorts of legs, and especially the webs of swimming 

 ' birds, are often crosswise or otherwise marked by lines, without these being 

 strong enough to produce plates ; this is a condition analogous to the little 

 raised lines and depressions seen on our own palms, and especially our 

 finger-tips. Occasionally, the plates of a part of the leg become so devel- 

 oped as to form actual serration; seen on the hinder edge of the tarsus of 



Booted" tarBua, of a robin. 



Fig. 10. Sctitellate tavsiis, 

 of a cat-bii'd. 



Fig. 11. 6. Sc.iiteUate tarsus, of a 

 pigeon; a. reticulate tarsus, of a 

 plover. 



§ 81. When an unfeathered tarsus shows on its front surface no divisions 

 of the podotheca, or only two or three divisions close by the toes, it is said 

 to be booted, and the podotheca is said to be fused. (Fig. 9.) This con- 

 dition chiefly occurs in higher Oscines, and is siijoposed by many, particu- 

 larly German ornithologists, to indicate the highest type of structure ; but 

 it is also found in some water birds, as Wilson's stormy petrel. It is not a 

 very common modification. Among North American birds it only occurs 

 in the following cases: — Genera Turdus (1), Oinclus (5), Saxicola (6), 

 Sialia (7), Regidus (9), OhamcBa9 (11), Myiadestes (52) and Oceanites 

 (307)7if and even these birds, luhen young, show scutella, which disappear 

 with age, by progressive fusion of the acrotarsial podotheca. 



§ 82. The Crus, when bare below, may present scutellation either before 



• or behind, or both, as is seen in many waders where the crus is largely 



naked; often again, the crural podotheca may consist of loose, sottish, 



■ movable skin, not obviously subdivided: sometimes it is truly reticulate, 



as in the genus Heteroscelus (221). 



§ 83. The Tarsus, in general, may be called subcylindrical ; it is often 

 quite circular in transverse section ; very rarely thicker across than fore-and- 

 aft (as in penguins) ; but very often thicker in the reverse direction. 

 When this transverse thinness becomes noticeable, the tarsus is said to be 



