3 ° 
Sclater on the Sy sterna Avium. 
Subordo I. Ayes Carinate. 
Series 
ALgithognathina. 
Series 
Desmognathina. 
4. Coccyges. 
5. Psittaci. 
6. Striges. 
7. Accipitres. 
8. Steganopodes. 
9. Herodiones. 
10. Anseres. 
Schizognathina. 
11. Columbae. 
12. Gallinae. 
Series 
Dromceognathina. 
19. Crypturi. 
Series 
1. Passeres. 
2. Cypseli. 
3. Pici. 
13. Opisthocomi. 
14. Grues. 
15. Limicolae. 
16. Gaviae. 
1 7. Pygopodes. 
18. Impennes. 
Subordo II. Aves Ratitve. 
20. Apteryges. 
21. Struthiones. 
I will now proceed to make a few remarks upon each of these 
orders, and to state where I think there are improvements still 
to be effected in the arrangement. It must, however, be alw r ays 
recollected that, although a linear system is an absolute necessity 
for practical use, it can never be a perfectly natural one. It will 
always be found, in any linear arrangement, that certain groups 
are nearly equally related to other groups at quite different parts 
of the series, and that it is a question of no little difficulty with 
which of these to place them ; but we must, nevertheless, do our 
best to make the most natural linear arrangement that is possible 
for practical use. 
1 . Passeres. 
After eliminating the Scansores and Fissirostres of the Cuvier- 
ian system, the remainder of the Insessores constitute a tolerably 
homogenous group, which, it is now generally acknowledged, 
form one of the main divisions of the Class of Birds. They are 
the Passerinas of Nitzsch,* the Oscines of Sundevalfs k Tenta- 
men,’ f the Coracomorphas of Huxley ; but I see no reason why 
we should not retain for them the old Linnean name of Passeres. 
There are still several forms regarding which their collocation 
in the Passeres thus understood is a matter of dispute. These 
are mainly as follows : — 
x. Upupa. Sundevall places Upupa near the Larks, at the 
commencement of his second series of Oscines (the “Oscines 
* ‘ Obs. de Avium arteria carotide communi.’ Halse, 1829. 
fin Sundevall’s former arrangement (Orn. Syst. 1836) they were denominated 
Volucres, and divided into two main groups, Passeres and Oscines. 
