THE EXTERNAL STRUCTURE OF BIRDS. 163 
may be entirely reticulate. Rarely the tarsus may be “ greaved ” 
(continuously sheathed) in front and yet scutelliplantar. 
The upper surface, or dorsum, of all the toes—called the 
acropodium—is almost always scutellate. Their under surface 
is in general minutely marked, but may develop small wart-like 
structures— pads” or tylari—as may be seen in Hawks. 
Claws.—Lvery digit of a bird’s foot is provided at its end with 
a horny claw, more or less curved and pointed at its extremity, 

DIAGRAM oF HrrperMAL Covering or Tarsus AnD Diairs, 
a. Reticulate form (Plover). 4. Scutellate and reticulate form (Pigeon). 
c. Booted or greaved laminiplantar form (Robin). d. Scutellate lami- 
niplantar tarsus (Cat-bird—Mimus carolinensis). 1t-4 +. Digits. trs. 
Tarsus, 3fcl. drd digit from tarsus to end of claw. (After Coues.) 
except that the hallux, when in a rudimentary condition, may 
be clawless. Claws vary as to length and strength. They are 
exceptionally long and all straight in the Jacanas, especially 
that of the hallux. They are at their maximum of strength, 
as well as much curved and acutely pointed, in the Hawk and 
other birds of prey. They are but little pointed in such birds 
ia oe Fowl and the Pigeon, but most obtuse of all in the 
rebe. 
M 2 
