1872.1 



ON THE BIRDS OF CELEBES. 



153 



smooth plate ha.? 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) 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) 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 (mufi. nostr.) a third 

 band has been partially arrested in its development, the groove 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 witli only two ; while in that given by Schlegel and S. Miiller 

 {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. 



Dime7isions. 



It will be seen that the bill increases in length after the Avings 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, appears to become absorbed, 

 and to retreat as the bird increases in age ; or, as the anterior edge becomes more and more 

 perpendicular to the culmen, it perhaps wears oft", or is broken off. This can be traced in one 

 example — the indent or hollow from which the fore part of the casque sprung, and in which it 

 was attached to the culmen, a groove shaped like a V, three quarters of an inch long, not 

 being filled up. 



Buceros suleatus, Temm., from the Philippines, and B. corrugatus, Temm., from Borneo, 

 belong to the same genus. 



Tr. Z. S. viii. 

 p. .51. 



