390 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



El precedente I take to refer to the preceding species, the yapu 

 {Ostinops decumanus) that has a light colored bill which contro- 

 verts Vieillot's statement that in soUtarius the bill is black. 



Though formerly placed in the genus Amhlycercus the species 

 soUtarius is apparently a cacique. Amhlycercus holosericeus has a 

 strongly operculate nostril, no crest, and the eighth primary shorter 

 than the second, while ArchipJanus solitarms has the nostril non- 

 operculate, the eighth primary longer than the third, the wing 

 longer, and a decumbent crest. 



The differences between soUtarius and holosenceus have been dis- 

 cussed recently by Miller,^^ but Avithout making a change in their 

 current status. Todd^^ includes soUtarius in the genus Archi- 

 plmius Cabanis, a group segregated by Miller in the paper cited 

 above. I had recognized also that soUtatius must be removed from 

 Amhlycercus, and concur in Todd's allocation of it in the genus 

 ArcMplanus. The bill in soUtan^is is broader at the tip than in 

 Archiplanus aJMrostri.s, type of Cabanis's genus, but the form of 

 the decumbent crest and of nostril, wing, and tail are closely similar 

 in the two birds and indiqate clearly their relationship. Todd is 

 somewhat confused in the structural characters assigned to holoseri- 

 ceus and soUtarius, since it is hxAosei^iceus that has nostrils linear and 

 overhung by a membrance, not soUtarius as stated. 



The species here discussed was found at only three localities: 

 Las Palmas, Chaco, July 23 (adult male taken) and 26; Riacho 

 Pilaga, Formosa, August 14 (adult male) ; and Kilometer 200, west 

 of Puerto Pinasco, Paraguay, where three were seen September 25. 

 The birds were encountered in heavy brush where attention was 

 called to them by their harsh notes, quay quay. They were alert and 

 active and peered out with tail thrown over the back, but at any 

 alarm disappeared in dense scrub and were lost to view. The light 

 colored bill showed prominently, even when they were seen in tilting 

 flight across openings in the thickets. Like Archiplanus chrysop- 

 terus when feeding they poked and pried at leaves or loose bark 

 with open bill. On examining them I was struck by the utility of a 

 development noted frequently in some orioles, Amhlyrhaniphus, 

 other Icterids, and in the genus Sturnus among other birds, where 

 the angle of the lower jaw (the processus angularls posterior) is 

 prolonged behind the articulation as a slender bar. Contraction of 

 the bands of muscle thfit pass from this bar of bone to the side of 

 the skull force the tip of the lower jaw away from the upper, with 

 the articulation of the lower jaw with the quadrate acting as a ful- 

 crum. The bill is thrust into or under bits of bark, a rolled leaf, 



8«Auk. July, 1924. pp. 463-4G7 (received in WashinRton July 5, 1024). 

 8'Proc. Biol. Soc. Washin.gton, vol. 37, July S, 1024. p. 114. 



