Avifauna of Cetiiral America. 771 



It would seem, however, that South America, or prohahly, 

 to be move exact, the ancient Brazilian land-mass, is to be 

 regarded as the centre of origin of tliis group. This much 

 at any rate is the contention of Dr. Percy Lowe, who, in a 

 review of this genus (Mbis,-* 1912, pp. 489-528), attempted. 

 to trace the probable lines of migration of the two distinct 

 subdivisions into which it may be split — the more primitive 

 migrating northwards to occupy the Lesser Antilles, while 

 a differentiated offshoot of the ancestral stock pursued a 

 course by way of the Andean chain, through Central America, 

 and thence into the Greater Antilles. Dr. Lowe showed 

 that the distribution of these two races corresponded in a 

 somewhat remarkable way with the ancient configuration of 

 the land. 



The Starling-like Icteridse are also an exclusively New 

 "World group, and apparently arose in South America, 

 whence they have extended northwai'ds, for of the 186 recog- 

 nized species one-half (88) are South American, 31 occur in 

 Central America, and no less than 40 in Mexico ; but many 

 of these last are North-American species which come south 

 for the winter. Only 27 species occur north of Mexico. 



The Corvidse in the New World are represented by some 

 14 genera, chiefly Jays. Eight species of these genera are 

 found in Mexico and eight in Central America, while three 

 are confined to South America and three do not pass beyond 

 the confines of North America. Three genera — Calocilta, 

 Cissoloj)hus, and Psilurhinus — are confined to Mexico and 

 Central America. 



The evidence, on the whole, points to the Old World as 

 the centre of dispersal of the Corvidae ; but so far no 

 explanation is forthcoming for the dominance of the Jays 

 in the New World. 



Huxley made a memorable contribution to the study of 

 the geographical distribution of animals when (P. Z. S. 

 1868, pp. 294-319) he published his paper, " On the 

 Classification and Distribution of the Alectoromorphae and 

 Heteromorphse." In that contribution he pointed out the 

 striking differences between what he termed Peristeropod 



SER. X. VOL. JII. 3 F 



