v. ] SKEL E TON OF LO VfER LIMB. 2 1 3 



tinct Ichthyosaurus and Plesiosaurus, or the numbers of the 

 phalanges as we proceed from the first to the fifth digit 

 may be 2, 3, 4, 5, 4, as in Lizards, or i, 2, 3, 3, 2, as in Sala- 

 mandra, or 2, 2, 3, 4, 3, as in the Frog. In Birds (where the 

 fifth digit is never developed) the numbers of the phalanges 

 of the four digits, proceeding from the hallux, are mostly 2, 3, 

 4, 5 ; but they may be 2, 3, 3, 3, as in the Swifts, or 2, 3, 4, 3, 

 as in the Goatsuckers. It is by the number of their pha- 

 langes (4 and 5) that the two digits of the Ostrich are known 

 to answer to the fourth and fifth digits of other Sauropsidans 

 (e.g. Lizards) which have all five digits developed. 



FIG. 183. -LEFT FOOT OF A MONITOR LIZARD (Varanus). 



f, fibula; ;* mS, the five metatarsals, m * being that of the hallux: t, tibia ; 

 i, astragalo-calcaneum ; 2, cuboides ; 3, ecto-cuneiforme. 



The terminal phalanges may bifurcate, as in the short-tailed 

 Pangolin, or develop a fold of bone to support the claw, as 

 in Cats and Edentates, e.g. the Sloths. 



