50 



VISCOUNT WALDEN ON THE BIRDS OP CELEBES. 



of lateral folds. But the position which is occupied by the lateral plates in older 

 individuals is indicated by a dingy reddish brown colour. 



In the next stage (fig. 2, p. 48) the bill measures about one inch longer, and has 

 acquired the form which exists in the old bird ; but the cutting-edges are unbroken. 

 The casque is more inflated, appears more detached from the culmen, and reaches 

 further back on the crown of the head. In front it stands up at a right angle to the 

 culmen, and is much compressed. A thin, smooth plate has grown on the basal half of 

 the two mandibles ; but there are no traces of folds or grooves. The substance of these 

 plates seems to be secreted from the walls of the mandibles. 



In the fully adult bird (fig. 3, p. 49) the commissure is serrated, notched, and broken. 

 The casque extends back past the line of the eye. Anteriorly it is less compressed 

 than in the previous stages, although not so much swollen as the posterior portion. The 

 anterior edge stands at an acute angle to the culmen. The casque displays five distinct 

 folds or, rather, undulations. At the base of the mandibles the lateral plates are much 

 thickened. On each side of the maxilla they are divided by a single, deep, diagonal 

 groove into two equally broad flat folds. On the sides of the mandible there are two 

 grooves thus forming three similar folds. 



In the adult female (fig. 4, p. 49) the commissures are much broken and serrated. 

 The casque is smaller, the anterior edge rising at a right angle to the culmen. It is 

 also divided into five almost equal undulations or folds. The basal plates are divided 

 both on the mandibula and maxilla into three broad flat bands. In a second example 

 of a female (mus. nostr.) a third band has been partially arrested in its development, the 

 groove being being partly obliterated. While the female has certainly three flat bands 

 at the base of both the mandibles, it will be interesting to know whether the male has 

 never more than two at the base of the maxilla. In Temminck's plate (I. c.) the male 

 is figured with only two ; while in that given by Schlegel and S. Mtiller (I. c.) the 

 female is figured with three both above and below. The following dimensions are 

 taken from Menado examples in my collection. The bill is measured in a straight line 

 from the gape to the apex. 



Dimensions. 



It will be seen that the bill increases in length after the wings and tail have reached 

 their maximum. The inner circumference of the casque is greater in the youngest 

 than in the adult. The anterior part of the casque, at its union with the culmen, 



