6 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



The osteological and other internal characters of the Jacanidse are 

 the same as those given for the Jacani on p. 5. Additional (external) 

 characters are as foUows: 



Bill moderate in size, about as long as head, straight, compressed, 

 the rhinotheca usually developed basally into a more or less con- 

 spicuous frontal plate or "leaf," sometimes a rictal lobe or leaf also; 

 a more or less distinct metacarpal spur, in some genera conspicuously 

 developed, conical, more or less recurved, and sharp, m others small 

 and blunt; toes, including hallux, excessively elongated, with their 

 claws long, slender, straight, and acute, that of the hallux much 

 longer than its digit (sometimes three times as long) and slightly 

 recurved. 



In general appearance, as well as in habits, the Jacanidse resemble 

 members of the Rallidse more than they do the Charadrii, to which 

 they are far more closely related, since, like the latter, thej" differ 

 from the former in their schizorhinal instead of holorhinal nares, the 

 presence of well-developed basipterygoid processes, absence of occipi- 

 tal foramina and supraorbital grooves, emarginate instead of acumi- 

 nate apex to vomer, and other characters. In the metacarpal spur 

 they resemble certain genera of Charadrii, some of which also possess 

 a rictal lobe. In the character of their excessively elongated toes 

 and claws, however, they are entirely peculiar. These enable them 

 to walk and run with ease upon the surface of floating leaves of 

 aquatic plants. 



The Jacanidse are of intertropical distribution, but America pos- 

 sesses only one of the six recognized genera, the remainder being 

 confined to Africa (mcluding Madagascar), India, southern China, 

 Borneo, the Philippines, New Gumea, Australia, etc. 



KEY TO THE GENERA OF JACANID.E. 



a. Head -vrtthout frontal shield or lobes. 



b. Middle rectrices greatly elongated; tips of some of the primaries attenuated. 

 (India to southern China, Philippines, Java, etc.)- 



Hydrophasianus (extralimital).a 

 "bb. Middle rectrices not elongated; tips of primaries normal. (Southeastern Africa.) 



Microparra (extralimital).^ 

 'oa. Head with a frontal shield. 



b. Frontal shield without free margins. (Africa, including Madagascar.) 



Actophilus (extralimital).c 



« Hydrnphasianus Waglcr, Isis, 1832, 270 (type, by original designation, Parra sinen- 

 sis Gmelin = Trmgra chirurgus Scopoli). — Hydrophasis (emendation). 



& Microparra Cabanis, Journ. fiir Orn., 1877, 349 (type, by original designation, 

 Parra capensis Smith). — Aphalus Elliot, Auk, v, July, 1888, 292 (type, by original 

 designation, Parra capensis Smith). (Monotypic.) 



This form not seen by me. 



c Phyllopezus (not of Peters, 1877) Sharpe, Cat. Birds Brit. Mus., xxiv, 1896, 76 

 (type, Parra africana Gmelin). — Actophilus Oberholser, Proc. Ac. Nat. Sci. Phila , 

 June 2, 1899, 202 (new name for Phyllopezus Sharpe, preoccupied). (Two species.) 



