FAMILY CORVIDAE 



45 



from northeastern Mexico. Their illustration of a plucked specimen 

 shows clearly the position of the distended sac, which externally pro- 

 jects from the space between the bifurcation of the two arms of the 

 furcula. This verifies the anatomical details given by Crandall, with the 

 appropriate suggestion that to avoid confusion with terms current for 

 the air sac system in birds it be called the furcular sac. 



During fieldwork in southern Veracruz, Mexico, in early 1939, I 

 found the nominate race, Psilorhinus m. morio, common, and heard 

 their curious explosive sounds regularly. When they flew overhead, a 

 yellowish spot appeared on the breast, though at rest this was not visible. 

 With birds in the hand I found that the furcular sac was bare except 

 for a few scattered filamentous feathers, mainly on the lower portion. 

 The skin of the upper, anterior half was thin and partly transparent. 

 The thicker-walled lower end, measuring approximately 15x20 mm, 

 was dull buff in color. Posteriorly, the sac narrowed immediately to a 

 slender tube as it entered the breast behind the furcula, and continued 

 thus to its connection with the interclavicular air sac. In jays recently 

 dead, I could inflate and deflate the sac by compressing and releasing 

 the posterior part of the body so that air was forced into it and then 

 withdrawn (Wetmore, Proc. U. S. Nat. Mus., vol. 93, 1943, pp. 298- 

 299). 



Hardy, in his revision of the New World jays (Condor, 1969, p. 

 363) lists the Brown Jay in the genus Cyanocorax, subgenus Psilor- 

 hinus, as Cyanocorax morio. As the curious furcular sac has no known 

 approach in any other species of the family, it seems appropriate to 

 place this jay in a distinct genus as Psilorhinus morio. 



CYANOCORAX AFFINIS ZELEDONI Ridgway: Black-chested Jay, 



Choch6 



Figure 4 



Cyanocorax affinis zeledoni Ridgway, Auk, vol. 16, no. 3, July 1889, p. 255. (Tala- 

 manca, Costa Rica.) 



Fairly large; head, foreneck, and upper breast black; rest of lower 

 surface pale yellow; wings and tail bluish; tail with a broad white tip. 



Description. — Adult (sexes alike), head, foreneck, and upper chest 

 black; spot on posterior half of superciliary area, another on posterior 

 half of lower eyelid, and a malar streak, bright blue; nape purplish 

 blue; lower hindneck, back, scapulars, and rump dull, somewhat bluish, 

 brown; wings, upper tail coverts, and tail dull blue, the tail tipped 

 broadly with pale yellowish white. 



