1865.) MR. P. L. SCLATER ON LEPTOSOMA DISCOLOR. 685 
(where the feathering commences), and consist of a narrow diagonal 
slit, just as in the genus Hurystomus. But in Hurystomus the aper- 
tures lie, as is the case in the majority of birds, at the base of the 
beak close to the frontal plumes. On examining the skeleton of 
Leptosoma we see at once that this remarkable formation has been 
effected by the elongation of the basal portion of the beak, and that 
the lateral coverings of the nasal passages (alee nasi), which in most 
birds are entirely membranous, have in this form become completely 
ossified, so as to add very materially to the strength of the upper 
mandible. 
A very similar formation occurs in Eurystomus, but is not carried 
to the same extent, the covering of the nasal passages remaining 
membranous in this form. 
The wings of Leptosoma are of moderate length, reaching to about 
half the length of the tail from its base. The primaries are ten in 
number, the third, fourth, and fifth being nearly equal and longest, 
the second half an inch shorter, and the first more than an inch 
shorter again, being about equal to the eighth. The first six are 
narrowed towards the apex ; the remaining four are broad-tipped like 
the secondaries. The secondaries are twelve in number. 
The tail consists of twelve rectrices of nearly equal length, and 
squared at the apices. 
The feathering of Leptosoma presents some remarkable characters. 
The body-feathers have a long downy auxiliary plume, longer than 
Fig. 3. Fig. 4. 
half the length of the feather itself. In Hurystomus there is a similar 
auxiliary plume, but not quite so highly developed. In the Cuculide, 
