E. LÖNNBERG, ON THE RHAMPHOTHECA OF BIRDS. 509 



Finally this has found a maximum and excessive develop- 

 ment in Didunculus which in this respect almost resembles 

 a bird of prey. The proximal elements of the bill of the 

 döves have become reduced to softness forming a cere, bnt 

 nevertheless those parts which correspond to the nasalia 

 are differentiated as a kind of scale-like opercles more or 

 less developed in different species. On the lower jaw the 

 feathered tract forms a projecting angle and in continuation 

 of this a groove extends forward indicating the division 

 between the infralabial and submandibular elements as in 

 the Limicolce althongh the whole covering of this region is 

 rather soft in the Columbce. 



When a horny shield has disappeared as snch and has 

 been substitnted by soft skin the growth of feathers is made 

 possible and feathers often encroach npon the former horny 

 area. Examples of snch a development have been fonnd 

 several times among the already treated gronps and still 

 more striking examples shall soon be exhibited again, bnt 

 among the Columbce Lopholcemus may be mentioned, for in 

 that pigeon the internasal tract is fnlly beset with feathers. 



For the same reason and to answer the same pnrposes 

 as in the Falconiformes the bill of the Striges has been 

 shortened, because a long bill wonld not have suited a bird 

 of prey which catches its prey with the claws and nses the 

 bill for tearing it to pieces. In an analogous manner as in 

 the hawks (conf. above p. 500) the rhamphotheca of the owls 

 consists according to my opinion only of a highly developed 

 rostrale above and a mentale below while the basal elements 

 ar rednced to a cere. 



The rhamphotheca of the Parrots is transformed in an 

 analogons manner as that of the Owls, although the former 

 birds being vegetarians nse their powerfnl beaks as nsefnl 

 tools for other purposes. Bnt in just the same way the upper 

 rhamphotheca of the Parrots consists of a strong rostrale 

 and the lower one of a mentale. The cere of the Parrots 

 1 regard in a similar way as that of the Owls viz. as a 

 rudiment of the basal elements of an original rhamphotheca. 



The cere of the Parrots and that of the Owls show several 

 analogous treats. Among those may be noted the fact that 

 the cere in many Parrots as well as Owls forms a bulb 

 round the nostril. This bnlb may be taken for the homologon 



