EXTERNAL PARTS OE BIRDS.— THE FEET. 125 



the onvokipc in various ways by cross lines. Plates are of various shapes and sizes, aud 

 grade usually into true scutella, from which however they are generally distinguished by being 

 smaller, or of irregular contour, or not in definite rows, or lacking the apitearauce of imbrica- 

 tion ; but there is no positive distinction. They are oftenest Iteaagoital (six-sided), a form best 

 adapted to close packing, as shown very perfectly in the cells of the honey-bee's comb; but 

 they may have fewer sides, or be 2'oli/goiial (many-sided), or even circular; when crowded in 

 one din^ction aud loosened in another the shape tends to be oval or even linear. A leg so fur- 

 nished is said to be reticulate : the reticulation may be entire, or bis associated with scutellation, 

 as often happens (tig. 38, tj). A particular case of reticulati(jn is called (jranulation (Lat. 

 (iramim, i\ grain): when the plates become elevated into little tubercles, roughened or not. 

 iSucli a leg is said to be granular, fjranulatcd, or rugose: it is weU shown by parrots, and the 

 tish-hawk {Pandioii). When the harder sorts (jf scales or plates are roughened without 

 obvious elevation, the leg is said to be acabrous nv scarious (Lat. ncabruni, a scali). But 

 ncat>rimts is also said of the under surfaces of the toes, when these develop sp(.'cial pads, oi- 

 wart-like bulbs (called fglari) : as is well sIiom'u in the sharp-shinned and many other hawks. 

 The softer sorts of legs, and especially the webs of swinnning birds, are often marked crosswise 

 or amceHa<8(Z with a lattice work of lines, these however not being strong enough t(i produce 

 plates ; it is more like the lines seen on our palms and finger-tips. The ])lates of a part of the 

 leg occasionally develop into actual serrations : as witnessed along the hinder edge of a 

 grebe's tarsus. AV^hen an unfeathered tarsus shows nv divisions of the podotheca in front 

 (along the acrotarsium), or only two oi' three scales close by the toes, it is said to be hooted or 

 greaved ; aud sucli a podotheca is holothecal (Gr. S\os, kotos, wliole, entire, and drjKri ; tig. lid). 

 The generic opposite is schizothecal (Gr. <rx''f"' ' eleave), whetlier by scutellation or reticida- 

 tion or in any other way the integument may Ik.' i-ut up. A booted or holothecal tarsus chiefly 

 occurs in the higher Oscines, and is supposed by many, particularly German ornithologists, to 

 indicate the highest type of bird structure. It is, ho\\'ever, found in a. few water birds, as 

 Wilson's stormy petrel and other species of Oceanites. It is not a common modificatiiju. 

 Exceptions aside, it only occurs in connection with an equally jiarticular conditicju of the 

 .ndes and back of the tarsus, or plaida. In ahnost all Oscine Piisseres (Alaudidtc are an 

 exception), which constitute the great bulk of the large oi-der Passercs, the ])lauta is covered 

 with (jue pair of plates or lamiiue, one on each side, meeting behind in a sharp ridge ; a condi- 

 tion called latniniplcintar, iu distinction from the opposite, scatelliplitiildr. state of tiie parts. 

 A holothecal podotheca only occurs iu connection with the laminiplantar condition, the combi- 

 nation resulting in the perfect '"boot." Among North American birds, the genus Oceanites 

 aside, it is exhibited by the folk>wing genera, and by these only ; Tardus, Cinchts, Saxicola, 

 Sialia, Begiilus, Cyanecula, Phylloscopus, Clianuea, 3Ii/iadestes : aud even birds of these 

 genera, when young, show scutella which disappear with age by progressive fusion of the 

 acrotarsial podotheca. (Compare figs. 36, .'57.) 



The Crus, when bare of feathers below, may, like the tarsus, be scutellate or reticulate 

 before (jr behind, or both ; such divisions of the crural integument being commonly seen in 

 long-legged wading birds. Or, again, this integunnnit may be hxise, soflisb, and movalile, not 

 obviously divided, aud passing directly into ordinary skin. 



The Tarsus, in general, may be called sulicylindrical : it is often quite circular in cross- 

 section ; generally thicker fi-om before backward, and only rarely wider fi'oni one side to tla^ 

 other than in the opposite direction; but such a sha])e as this last is exhibited by the p(uiguins. 

 When the transverse thinness is noticeable, the tarsus is said to be compressed; aud such 

 <!ompression is very great in a loon, in which the tarsus is almost like a knife blade. iQuite 

 <'.ylindrieal tarsi occur chiefly when there are similar scales or plates before aud behind, as 



