228 GENERAL ORNITHOLOGY. 
will be found, generally down to species at ven varieties. They are to be used as follows 
(after the preceding lessons have been learned) : — 
We have in hand a bird we do not know, and the name of which we wish to ascertain. 
Suppose it to be that common species which builds the nest of mud upon the bough of the 
apple-tree and lays greenish-blue eggs. ‘To what family does it belong ? 
The Key opens with an arbitrary division of our birds according to the number and 
position of their toes. Our specimen, we see, has four toes, three in front, one behind. It 
therefore comes under IV. Going to IV., we read: 
Hind toe — inserted above the level of the rest, etc. 
—not inserted above the level of the rest. . . . (Go to B.) 
Our specimen has the hind toe not inserted above the level of the rest. Going to B, we find 
five alternatives. Our bird presents no one of the special characters of the first four alterna- 
tives, and this determined takes us tog. There we find: 
(g) Primaries —10 ; the 1st (never spurious), etc. 
—10; the ist (spurious or), etc. . . . (Go to 7) 
— 9; the 1st (never spurious), ete. 
In this case the bird has obviously a spurious first primary, not nearly two-thirds as long as 
the longest. Going to 7;— 
(i) Tarsus — ‘‘ booted ” ; wings — shorter than, etc. 
— longer than tail; tail— double rounded. 
—not double rounded. . . . . TURDID&, p. 240. 
Thus (provided we have taken the trouble to inform ourselves what ‘‘ spurious first pri- 
mary” and ‘‘ booted tarsus” mean), the key conducts to a family, by presenting in succession 
-certain alternatives, on meeting with each of which, we have only to determine which one of 
the two or more sets of characters agrees with those afforded by our specimen. There will 
not, it is believed, be any trouble in determining whether a given character is so, or is not so, 
since only the most tangible, definite, and obvious features have been selected in framing the 
key. After each determination, either the name of a family is encountered, or else a reference- 
letter leads on to some new alternative, until by a gradual process of elimination the proper 
family is reached. After a few trials, with specimens representing different groups, the process 
will be shortened, for the main divisions will have heen learned; still the student must be 
careful how he strikes in anywhere except at the beginning, for a false start will soon set him 
hopelessly adrift. The key has been tested so thoroughly that there is little danger of his 
running off the track except through carelessness, or misconception of technical terms; but 
there is no exeuse for the former, and the latter may be obviated by the Glossary at the end of 
the book, and cspecially the foregoing General Ornithology, § 3, which should be consulted 
when any doubt arises. Time spent upon the preliminary lessons will be time saved in 
the end. 
At page 240, as indicated, the family Twrdide@ is fully characterized, and its sub-families 
and genera are analysed. The bird in hand should answer all the characters of the family and 
those of one of the sub-families, Twrdine, and one of the genera, Turdus. The analysis of 
the species of Turdus should show the specimen to be Turdus migratorius, the Robin. Under 
the head of that species, No. 1 of the List, will be found a fair description and various other 
particulars. 
If there be any difficulty in going at once to/the family, the student may try the key to 
the orders and sub-orders, and get on the track in that way. 
Directions for measurement have already been given (p. 24). In comparing measure- 
ments made with those given in the Synopsis, absolute agreement must not be expected ; 
individual specimens vary too much for this. It will generally be satisfactory, if the discre- 
