ON THE ORIGIN OF GENERA. II5 



The Clamatorial type of the Passeres exhibit larval characters 

 in the non-development of the singing apparatus, and the scaled 

 or nearly naked tarso-metatarsus. These are chiefly South Amer- 

 ican. 



Of Mammalia, the placentals without enamel on their teeth, 

 which, in this respect, never reach the full development of the 

 class, whose dentition is also monophyodont, i. e., the Edentata, 

 inhabit only the Southern Hemisphere, and almost altogether the 

 Neotropical region. The implacental Mammalia, also (except in 

 one tooth) monophyodont, which approach birds and reptiles in 

 so many respects, are confined to the Southern Hemisphere, and 

 chiefly, as all know, to Australia. 



Of the Quadrumana, the Platyrrhine group is known to be in- 

 ferior to the Catarrhines : the former presents an entirely embry- 

 onic condition of the os tympa7iicum, which is passed by the latter 

 in early age ; * it contains also the only clawed genus of the true 

 monkeys. It is confined to the Neotropical realm. To Madagascar, 

 also of the Southern Hemisphere, and nearest in many ways to 

 the Neotropical, pertain the lowest families of the Quadrumana, 

 the Lemuridae and Chiromyidas ; the former presenting brains 

 without convolutions, and approaching in many ways the Insec- 

 tivora ; the last imitating, at least, a Eodent. 



There are also other reasons for the inferiority of South Amer- 

 ica. Its deer, which are few, include those which never produce 

 more than the ^^dague," or the first horn of the northern Cervus, 

 and also those which never get beyond the fourth step in the de- 

 velopment of the lower group of R. Nearctica. 



The Loricariidae, of South America, I am informed by Prof. 

 Agassiz, possess the foetal pupil of the vertebrate type. 



If we glance at Coleoptera we find the great predominance of 

 the groups with undeveloped tarsus, the three- and four-jointed 

 Trimera and Tetramera, and of the lower group with undeveloped 

 sternum, f the Rynchophora, in the Neotropical region. 



Among Lepidoptera it is known that the most gigantic of the 

 species of the Neotropical region are Noctuidae (Erebus, etc. ), and 

 that in that region this low type of the order reaches its greatest 

 development. The largest forms of the Regio Nearctica, as well 

 as Pal^arctica, are representatives of the higher type of the Satur- 



* See Dr. H. Allen, "Proceed. A. N. S.," Phila., 186Y. 

 \ Leconte, American Association, 1867. 



