8 LIEUT.-COLONEL SYKES ON THE 
less the detailed, result of my inquiries; and it must suffice to say that I quickly 
found the tongue and the ceca of considerable importance in indicating affinities or 
dissimilarities between genera. As an instance I may point out the Ciconia leucoce- 
phala, which at this moment stands in ornithological works of the highest authority, as 
an Ardea, but which its short tongue at once separated from that genus: and its double 
short or rudimentary ceca, instead of a single short cecum, and the remarkable colour 
of its iris contrasted with the prevailing yellow colour in the Herons, afforded further 
proof of its distinction. 
To be brief, and yet to afford sufficient evidence of my views connected with the 
subject of the present paper, I have put into a tabular form some of the characters of 
the Tetraonide, which I consider likely to assist to give precision in the formation of 
generic characters ; and I have added those of a Dove and a Pigeon, for the sake of 
comparison with the organs of Pterocles ewustus. ‘The very close resemblance in the 
form of the tongue, the ceca, the proportional length of the intestines and ceca, and 
the colour of the irides in the birds whose affinities are very close, is remarkable, 
although there are some differences in the form of their bills. The Quails, the Part- 
ridges, and the Francolinus Ponticerianus, have such trifling variations that the organs 
noticed may be considered almost identical. When we proceed to the three-toed Hemi- 
podii, we find with similar tongue and ceca, a more elongated form of bill, and a dif- 
ferently coloured iris: the tongue and ceca indicate similar habits with the Quails and 
Partridges ; but the colour of the irides, the form of the bill, and the three toes, mani- 
fest generic distinctions. Although I possessed many specimens of the Francolinus 
spadiceus alive, and no doubt subjected them to the usual examinations, I observe that, 
by some chance, the sketch of the ceca and the proportional lengths of the intestines 
are omitted in my note-book. I cannot therefore, at this period of time, say whether 
they correspond with the figure and measurements of those organs in the Partridges and. 
Quails ; but as the real Francolin differs from them in habits, it is probable that there 
is sufficient difference in the proportions if not in the form of the organs to establish a 
generic distinction. 
Applying the test of all the above characters to Pterocles exustus, it is apparent that 
it has the aspect, the tongue, and almost the bill, with the air and flight of a Pigeon ; 
and I observe, pigeon-like, that there is not, in my notes, any mention of a gall- 
bladder. But when we compare the remaining organs with those of Columba tigrina 
or Columba Ginas, we find that it has the ceca and iris of the birds of the Partridge 
family ; but the intestine and ceca are proportionally a good deal longer than in those 
birds: it may be considered, therefore, intermediate between the Tetraonide and Co- 
lumbide. I may point out that, with the same form of bill and tongue, the Doves differ 
from the Columba Gnas in being totally destitute of ceca, the latter having rudimentary 
ceca; and it is worthy of inquiry to ascertain whether this difference be constant be- 
tween the Doves and Pigeons proper. 
