100 GENERAL EVOLUTION. 



The first comparison of these groups was made by Wiegmann 

 (Herpetologia Mexicana), who employed, however, only the Scin- 

 cidae and Lacertidae, and could not include the mauy types made 

 known since his day. 



From the class Aves I have selected only the homologous series 

 of the Clanatorial and Oscine Passeres. Naturalists more fully 

 acquainted with the genera could probably increase the examples 

 of heterology largely. Each group furnislies us with carnivo- 

 rous, insectivorous, and frugivorous forms ; each with walkers, 

 climbers, and sedentary genera ; each with butcher-birds, thrushes, 

 warblers (not in song !), wrens, and fly-catchers. Each and all of 

 these types are teleologically necessary to any country complete in 

 the wealth of nature, and to each geological period. 



Clamatores. Oscines. 



I. Tree-climbers, with long hind toe and tail feathers stiflfened and acute. 



Dendrocolaptidw. Certhiidoe. 



II. Terrestrial in part, with the tertials as long as the primary quills. 



Geohatidce. Motacillidcp.. 



III. Tree-perchers with hooked bill, graduating from powerful to medium and 

 slender. 



Formicariidce Turdidce. 



Thamnophilus. Bill strongest, hooked. Lonius. 



Formicarius. " moderate. Turdus. 



Formicivora. " weak. Bylvia. 



Rhamphoccemus. " slender (wrens). troglodytes. 



IV. Fly-catchers with flat bill and weak legs ; wait for their prey and take it on 

 the wing. 



TyrannidcB. Muscicapa et aif . 



V. Flat-billed berry and fruit eaters. 



Cotingidce. BombycillidoB. 



From the Mammalia the well-known series of the Marsupialia and Placentialia 

 may be chosen. 



Placentialia. Marsupialia. 



I. Toes unguiculate, in normal number ; sectorial teeth ; i. e., one or more molars 

 with one or no internal tubercles ; canines strong : 



Carnivora. JSarcophaga, 



I. Digitigrade. 

 Toes 5 — 4. 



Ti'ue molars f (upper incisors more numerous in some). 

 Amphicyon. Thylacinus. 



II. Plantigrade ; molars tubercular. 

 a. Posterior molars ^. 



* * Dasyuridae. 



aa. Posterior molars |. 

 TJrsidse. * * 



II. Toes unguiculate ; molars with more than one row of pointed tubercles ; canines 

 weak or none ; incisors large. 



