342 My. P. L. Sclater on the present 
ments on the Grayian system in the remainder. In the in- 
troduction to the ‘Nomenclator, accordingly, I gave the 
subjoined scheme as that which I proposed to employ for the 
general arrangement of living birds, dividing them into 21 
orders, as follows :— 
Subordo I, Aves CARINATA. 
Series Series Series Series 
igithognathina.  Desmognathina.  Schizognathina. Dromeognathina. 
1. Passeres. 4, Coccyges. 11. Columbee. 19. Crypturi. 
2. Cypseli. 5. Psittaci. 12, Galline. 
3. Pici. G6. Striges. 13. Opisthocomi. 
7. Accipitres. 14, Grues. 
8. Steganopodes. 15. Limicole. 
9. Herodiones. 16, Gaviee. 
10. Anseres. 17. Pygopodes. 
18. Impennes. 
Subordo II. Aves Ratirz. 
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 improve- 
ments stiil to be effected in the arrangement. It must, 
however, be always recollected that, although a linear sys- 
tem 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 Cu- 
vierian system, the remainder of the Insessores constitute a 
tolerably homogeneous group, which, it is now generally 
acknowledged, form one of the main divisions of the Class 
of Birds. They are the Passerine of Nitzsch*, the Oscines 
* Obs. de Avium arteria carotide communi.’ Hale, 1829. 
