74 
Sclater on the Sy sterna Avium . 
be better for the future to restrict the term Coccyges to these two 
families. The question then is, what shall we do with the re- 
maining groups of the order? The arrangement of them by the 
structure of the feet, according to Prof. Huxley’s scheme, al- 
though very simple, is not quite natural. Lefttosoma, for instance 
(as I believe I first showed in 1865* * * § ), although the outer toe is 
more or less reversed, must certainly come near the Rollers 
(Coraciidas) ; and Colius would now appear to be nearly related to 
the same group, f although its foot-structure is by no means sim- 
ilar. There seem in fact to be several different categories com- 
bined in the order Coccyges thus considered. First we have the 
Lipoglossag of Nitzsch, consisting of the four families Alcedinidae, 
Bucerotidae, Upupidae, and Irrisoridae.J These all belong to the 
Piciformes of Garrod,§ and all the best authorities are pretty 
well agreed as to their consanguinity. Along with these must 
come the Cuculinae calopterae or Todidae of Nitzsch, containing 
also four families, which, to my mind, are also closely related — 
namely the Meropidae, Coraciidae, Momotidae, and Todidae. The 
two last-named groups are united by Garrod into one family. || 
They all four have twelve tail-feathers, a naked oil-gland, and 
caeca. But to these must be added, as aberrant appendages 
(which sadly mar the uniformity of the group) , the Leptosomidae 
and Podargidae and, as it would appear from Prof. Garrod’s re- 
searches, the Coliidae. Leptosoma , as stated above, is clearly 
more allied to the Rollers than to any other form. Podargzis 
cannot be left with the Caprimulgidae, looking to the conformation 
of its palatal bones, and comes in best here, whereas Nyctibius 
belongs truly to the Caprimulgidas.ft After Garrod’s exhaustive 
disquisition on Steatornis,§§ we can no longer complain that its 
structure is unknown ; but it becomes still more difficult, owing 
to its numerous peculiarities, to arrange this most extraordinary- 
bird in a satisfactory place in the series. It must certainly be 
either put in here or placed as a separate order next to the Striges. 
Perhaps the former plan is for the present the most convenient. 
* P. Z. S. 1865, p. 682. Mr. Sharpe, in making the Leptosominae merely a subfamily 
of Coraciidae (Ibis, 1871, p. 285), appears to have entirely overlooked the structure of 
the feet. 
t Cf Garrod, P. Z. S. 1876, p. 416. II Huxley, P. Z, S. 1867, p. 445. 
+ Pterylography, p. 102. 1 + Huxley, /. c. p. 454. 
§ P. Z. S. 1874, p. 1 17. . §$ P. Z. S. 1873. p. 526. 
|| See P. Z. S. 1870, p. 101. 
