288 PALEONTOLOGY 



other animals, except as regards the web-footed order of 

 birds. 



Not more than three toes are directed forward ;* the fourth 

 when it exists, is directed backward, is shorter, usually rises 

 higher from the metatarsal, and takes less share in sustaining 

 the superincumbent weight. No two toes of the same foot in 

 any bird have the same number of joints. There is a constant 

 numerical progression in the number of phalanges (toe-joints), 

 from the innermost to the outermost toe. "When the back toe 

 exists, it is the innermost of the four toes, and it has two 

 phalanges, the next has three, the third or middle of the front 

 toes has four, and the outermost has five phalanges. When 

 the back toe is wanting, as in some waders, and most wingless 

 birds, the toes have three, four, and five phalanges respectively. 

 When the number of toes is reduced to two, as in the ostrich, 

 their phalanges are respectively four and five in number ; thus 

 showing those toes to answer to the two outermost toes in 

 tridactyle and tetradactyle birds. 



The same numerical progression characterizes the two 

 phalanges in most lizards from the innermost to the fourth ; 

 but a fifth toe exists in them which has one phalanx less than 

 the fourth toe. It is the fifth toe which is wanting in every 

 bird. In some Gallinacca, one or two (Pavo biccUcaratus) spurs 

 are superadded to the metatarsus ; but this peculiar weapon 

 is not the stunted homologue of a toe. Dr. Deane of Green- 

 field, United States, noticed, in 1835, impressions resembling 

 the feet of birds in some slabs of sandstone from Connecticut 

 River, and first, in a letter to Dr. Hitchcock, dated March 7, 

 1835, recorded his belief that they were the footsteps of a bird. 

 He prepared casts of the impressions, some of which lie trans- 

 mitted, with his opinion of their nature, in Professor Silliman, 

 Editor of the "American Journal of Science," in April 1835. 

 Dr. Hitchcock, President of Amherst College, United States, firsl 

 * Save in tin' Swift. 



