CORRESPONDENCE. 
To the Editors of the American Naturalist : 
I have recently had occasion to do some work which involved the 
comparison of genera in several groups of vertebrates, and in my 
studies I have made some discoveries which were rather surprising 
to me. For instance, I find our thrushes, in many works, distributed 
between two or three genera, our wood thrush being in the genus 
Turdus, the common robin in the genus Merula. The sole differ- 
ences I find recorded between these two genera are best shown in 
the deadly parallel : 
TURDUS. 
Bill much widened at the base. 
Tarsi decidedly longer than middle 
toe and claw. 
Spotted beneath. 
Of small stature and rather slen- 
der for 
MERULA. 
Bill little widened at the base. 
Tarsi little longer than middle toe 
and claw. 
Beneath mostly unicolor with 
streaked throat. 
Large, stout. 
Again, I find our pestiferous English sparrow in the genus Passer, 
while the purple finch is in the genus Carpodacus. 
between these two genera are: 
PASSER. 
Bill without nasal ruff. 
Culmen curved. 
Commissure little angulated. 
Gonys convex, ascending. 
Wing five times the length of 
carpus. 
Wing pointed by first three quills. 
Tail shorter than wings. 
Tail nearly even. 
Tarsus about equal to middle toe 
and claw. 
Lateral toes of equal length. 
Claws of lateral toes not reaching 
to base of middle claw. 
The distinctions 
CARPODACUS. 
Nasal ruff little developed. 
Culmen moderately curved. 
TEEN decidedly angulated. 
Gonys str: 
Wing not ppe five times the 
length of carpus. i 
Wing pointed by first three or 
four quills, 
Tail much shorter than wings. 
Tail forked. 
Tarsus shorter than middle toe 
and claw. 
Lateral toes subequal. 
Claws of lateral toes reaching the 
ase of middle claw. 
