Birds of Celebes: Bucerotidae. 
243 
The range of the PJioenicophaeinae ceases at Celebes, and the Celebesian 
subgenns Rhamphococcyx finds its nearest ally in the Javan snbgenns Rhinococcyx ; 
the Bucerotidae have a species, ranging from the Moluccas to the eastern bounds 
of Papuasia, whose nearest ally is found in Java, Borneo, Sumatra and the 
Asiatic countries to the west; while the two species of Celebes show affinity to 
the Philippine species. On the other hand the Hornbills, like the Coucals, 
lend very interesting proof to Wallace’s view of the recent simultaneous separa- 
tion of Borneo, Sumatra and Malacca - — not Java, Sumatra and Malacca, as 
might have been expected from the proximity of these islands. (See map VII). 
In view of the fact that three genera are peculiar to this section of the East 
Indies, one to Celebes, one to Palawan, two to the other Philippines, and that 
most species of the East Indies have a very restricted range, it is puzzling to 
find that Rhytidoceros is represented by one species only in all the islands between 
Halmahera and the Solomons, and is continued in a closely allied species, 
R. suhruficollis from Borneo to the Indo-Chinese countries; in other words Rhyti- 
doceros has only become differentiated into two species between British Burmah 
and the confines of Papuasia, while other Bucerotidae have become changed into 
eleven genera and 26 species in half the distance. 
An easy way of getting over this difficulty — and, as it would appear, 
most probably, the true way — is on the supposition that, while Rhytidoceros 
has extended its range by flight, most of the other East Indian Hornbills have 
become located in their several habitats by terrestrial changes, resulting in the 
production of barriers of sea over which the birds do not venture to fly. On 
examining the wings of the Hornbills a very curious structure of the primary 
quills is seen in most species. The first and second are very much attenuated 
and so weak that they are obviously of no use in flight: it would be of interest 
to know, indeed, whether they are freely extended in flight, or concealed under 
the larger quills. All the genera of the East Indian Hornbills are represented 
in the Dresden Mnseum, and we And that this modification of the quills is most 
pronounced in Anthracoceros, though nearly as well seen in Penelopides and Rhab- 
dotorrhinus; it is also found to a greater or less extent in Buceros^ Dichoceros^ 
Hydrocorax, Gymnolaemus^ Cranorrhinus^ Rhinoplax. It is not seen in Anorrhinus 
and Berenicornis] but in these two genera the wing is shorter and blunter than in 
most others, and does not appear adapted for sustained flight; Davison observed 
that the flight of Berenicornis — a contrast to other Hornbills — is noiseless 
(Str. E. VI, 104). With these two exceptions, the first primary has all the 
appearance that it is gradually dwindling away; it is probably an effect of 
disuse, combined with wear and tear of some kind^). In Rhytidoceros plicatus 
and undulatus the first primary is strong and not noticeably attenuated and may 
he of some service in flight; in R. suhruficollis it is attenuated about as much as 
1) As we believe caused by attrition, due to the position of tbe outermost remex underneath the ad- 
jacent remiges in the wing of these clumsy fliers. 
31 * 
