48 BULLETIN 133^ UNITED STATES NATIONAL MUSEUM 



killed, as they seemed less agile in rapid diving than other species of 

 grebes that I have taken. 



An adult male had the bill dull black, more grayish at base; iris 

 scarlet, with a narrow circle of baryta yellow around the margin of 

 the pupillar opening; outer face of tarsus, fourth toe, and under 

 surface of all the toes, dusky neutral gray; inner faces of first and 

 second toes washed with vinaceous buff; rest of tarsus and toes neu- 

 tral gray. 



AECHMOPHORUS MAJOR (Boddaert) 

 Colymhus major Boddaert, Tabl. Planch. Enl., 1783, p. 24. ("Cayenne.") 



This large grebe, when in full plumage, bears a striking resem- 

 blance to Holboell's grebe in pattern of markings and color. The 

 bill in general form agrees with Aechmophorus occidentalis (the 

 type of the genus), but is slightly heavier, while the base of the bill 

 is somewhat more heavily striated, and the nostril, bordered above 

 by a stronger membrane, is less elongate in form. In addition 

 the feathers on the sides of the mandibular rami form a more obtuse 

 angle and in most specimens do not extend as far forward, while 

 the streaked plumage of juvenile birds is strikingly different from 

 that of the plain gray of the chick of occidentalis. 



The species was first observed on the Parana River between Holt 

 and Zarate on October 9, 1920. On October 25 six or eight were 

 seen on salt water in the mouth of the Rio Ajo, below Lavalle, 

 Buenos Aires, and three, all in immature dress, were taken. Two of 

 these, preserved as skins, have indistinct dark streaks on the side of 

 the head, and lack the full bright color of adults. As my boat ap- 

 proached in the narrow river, these birds worked to one side and 

 finally made a long dive to allow me to pass. Three were observed 

 sleeping as they floated on the water, with the neck drawn back so 

 that the bill rested on the shoulder at the side of the neck with the 

 point ahead. As this threw the rounded head in the middle of the 

 back it produced a curious outline. From this attitude the birds 

 dived with no loss of time in swinging the bill to the front, an evident 

 advantage of this attitude over that assumed under similar circum- 

 stances by the pied-billed grebe in which the bill is turned and insert- 

 ed among the feathers of the back. One of the grebes taken here had 

 the end of one toe and part of the web on another bitten out as 

 though by a turtle or a small shark. The species seems to range 

 along the seashore, as on November 6 when I was on the coast below 

 Cabo San Antonio one washed ashore after a heavy storm, while on 

 the following day two more, one an adult male, were secured under 

 similar conditions. These had been dead for two days at least, and 

 were preserved either as skulls or skeletons. 



