E. LÖNNBERG, ON THE RHAMPHOTHECA OF BIRDS. 503 



the boundary-line is faint and disappears towards the tip. 

 The lower rhamphotheca is most probably composed of an 

 unpaired mentale and on either side two posterior elements 

 which are situated one above the other. The upper one of 

 these corresponds to an infralabial, the lower one is honio- 

 logous to a snbmandibular fnsed completely with mentale 

 so that it looks like a backward prolongation of this piece. 

 This is made probable by the feathered point or angle which 

 on either side extends from behind forwards between these 

 two supposed posterior elements, and in some specimens very 

 deeply so, becanse if there had not been any cleft in the 

 horny layer there is no reason why the feathered tract should 

 protrude in such a manner. 



The bill of the grebes and that of the divers are thus 

 as I think composed of the same elements and as they are 

 nsed in the same way the original elements of which they 

 are composed have been almost completely fused together in 

 both. 



In consequence of their habits and their diet the bill of 

 the Galli has become shortened, because a short bill is better 

 snitable for the picking of seeds and grains, pieces of herbs, 

 insects etc. from the ground. A reduction has therefore 

 taken place with regard to the preocular head region resp. bill 

 of the Galli and because this reduction has gone in a similar 

 direction as that which has transformed the bill of the Fal- 

 coni formes a certain analogous likeness may be seen between 

 representatives of these two different groups. Bostrale and 

 mentale are best developed, and the basal elements more or 

 less, reduced in both. This accounts for the superficial re- 

 semblance between for instance some Cracidce and some Ga- 

 thartiåce with regard to the bill. x In a primitive galliform 

 bird like Pipile the different elements of the bill may be 

 rather easily discerned. Behind the rostrale is a less horny 

 internasal and on the sides a labial. The lower rhampho- 

 theca has in addition to the mentale on either side an infra- 

 labial and a submandibular. In more specialised Galliformes 

 the reduction of the basal elements has proceeded further 

 but these may nevertheless be recognised in many instances. 

 In Partridges (for instance Caccabis), »Snow-Cocks» (Tetrao- 



1 This superficial likeness may even be extended to other primitive birds 

 of prey for instance if Crax and Polyborus are compared. 



