398 BULLETIN 5 0, UNITED STATES NATIONAL MUSEUM 



bb. Crowm buflFy heavily streaked with blackish or blackish brown, or, if nearly 

 solid blackish, the nape heavily streaked buflf and blackish. 

 c. Dark bars on rectrices very narrow, less than 8 nam. wide; crown prac- 

 tically solid blackish (Cuba and Isle of Pines). 



B. gtmdlachii, juv. (p. 407) 



cc. Dark bars on rectrices broader, usually more than 10 mm. wide; crown 



streaked buff and blackish, 



d. Outer webs of secondaries (as in folded wings) abundantly flecked with 



tawny chestnut in their terminal halves (Lesser Antilles, Trinidad, 



northern Venezuela to eastern Panama). 



B. anthracinus cancrivorus, juv. (p. 403) 

 dd. Outer webs of rectrices with no chestnut flecks. 



e. Size smaller, wing under 340 mm. (Pacific slope from southern 

 Mexico to Panama and to southern Ecuador). 



B. anthracinus sub tills, juv. (p. 405) 

 ee. Size larger; wing over 350 mm. (southwestern United States to 

 Panama and northern Colombia) . 



B. anthracinus anthracinus, juv. (p. 399) 

 aa. Underparts rufous-chestnut or blackish (adults). 

 6. General coloration rufous-chestnut. 



B. aequinoctialis, ad. (extralimital) 

 66. General coloration blackish or blackish brown. 



c. General color dark brownish, not definitely black (Cuba and Isle of 



Pines) B. gundlachii, ad. (p. 406) 



cc. General color blackish. 



d. Wing length under 345 mm. (Pacific slope from southern Mexico to 



Ecuador) B. anthracinus subtilis, ad. (p. 405) 



dd. Wing length over 345 mm. 



e. Feathers of nape spotted with tawny buff (Lesser Antilles to Vene- 

 zuela and eastern Panama). 



B. anthracinus cancrivorus, ad. (p. 403) 

 ee. Feathers of nape spotted with whitish (Southwestern United 

 States to Panama and northern Colombia). 



B. anthracinus anthracinus, ad. (p. 398) 



BUTEOGALLUS ANTHRACINUS ANTHRACINUS (Lichtenstein) 



Mexican Crab Hawk 



Adult (sexes alike in coloration). — General color uniform slate-black 

 with a strong glaucous cast ^^ on the back, neck, and breast; the head 

 generally darker black and without the glaucous cast; the feathers of 

 the crown, occiput, and nape with white bases more or less tinged 

 with pale tawny; upper wing coverts and remiges like the back, the 

 inner webs and the concealed portion of the secondaries usually (but 

 not always) mottled with grajnsh to hair brown to pale tawny-ochra- 

 ceous; the third to the fifth primaries longest, the first intermediate 

 between the eighth and tenth, the outer four with the inner webs 

 slightly sinuated; tail much shorter than wing, very slightly rounded 



•' Autumn birds (fresh plumage) have the glaucous cast more distinct than in 

 spring specimens. 



