BIRDS OF NORTH AND MIDDLE AMERICA 41 



Notwithstanding the great dissimilarity in appearance between the 

 typical rails, with their completely feathered head, long legs, and 

 slender toes, and the coots, with a conspicuous frontal shield and 

 conspicuously lobed toes, there is so complete a gradation from one 

 extreme to the other in forms of intermediate characters that it is 

 doubtful whether any subfamilies can be satisfactorily defined. Thus, 

 the gallinules (genera Gallinula^ Porphyrula^ etc.), while closely re- 

 sembling the coots in the form of the bill, development of the frontal 

 shield, and even in coloration, agree with the true rails in the unlobed 

 toes, and are insensibly connected with the latter by intermediate 

 forms. In short, while both the gallinules and coots have the rhino- 

 theca or covering of the maxilla continued upon the forehead, where 

 it widens into a more or less gibbous or expanded plate or frontal 

 shield, the coots alone possess conspicuous scalloped flaps or lobes 

 along the edges of the toes, in which respect the latter differ from 

 all other members of the family, and thus, for convenience only, may 

 be considered as constituting a subfamily. 



The family is cosmopolitan and is apparently a very ancient one 

 as a number of highly peculiar genera occur in remote oceanic islands. 



Students of Mallophaga have suggested a closer relationship than 

 that usually assumed between the rails and the very primitive kiwis 

 (Apterygidae) of New Zealand, but the birds themselves do not 

 bear this out with any trenchant characters. 



KEY TO THE NORTH AND MIDDLE AMERICAN GENERA AND SUBGENERA OF 



RALLIDAE ^s 



o. Toes without distinct lateral membranes (if with obvious narrow membrane 

 this on inner side only). 

 6. Without a distinct frontal shield, 

 c. Bill longer than head, culmen more than three-fourths as long as tarsus. 

 d. Loral antia at upper margin of nasal fossa, anterior outline of loral 

 feathering receding downward to rictus (sometimes very slightly 

 oblique or nearly vertical). 



e. Bill shorter, culmen much shorter than tarsus Aramides (p. 110) 



ee. Bill longer, culmen as long as or longer than tarsus. 



f. Bill swollen basally, its depth at base one-third length of exposed 

 culmen; flanks uniform Cyanolimnas (p. 98) 



" The following American genera of Rallidae have not been examined in con- 

 nection with the present work : 



AnuroUmnas Sharpe, Bull. Brit. Orn. Club, i. No. 5, 1893, p. xxviii. (Type, 

 by monotypy and original designation, Porzana castaneiceps Sclater and Salvin.) 

 South America (Upper Amazons). One species. 



8tictolimnas Biittikofer, Notes Leyden Mus., xv, 1893, 274. (Type, by mono- 

 typy and original designation, S. sJmrpei Biittikofer.) South America. Mono- 

 typic. Said to be a young Eypotaenidia with erroneous locality (Old World). 



Micropygia Bonaparte, Compt. Rend. Acad. Sci. Paris, xliii, 1856, 599. (Type, 

 by monotypy, Crex schomburgki Cabanis.) South America (Venezuela to Brazil). 



