284 University of California Publications in Zoology  [Vor.18 
of representative species, representing both the typical and out- 
lying forms included, and then a species which seemed to be fairly 
typical for the entire group was selected for careful study, and 
the minute structure of its remiges and body feathers worked out 
in detail. So far as possible, except in the Passeriformes, repre- 
sentatives, usually several, of each included family were examined 
to determine the constancy of the characters found in the selected 
type, and where important differences were found in other groups 
of the same order or suborder, their epiphyology was also worked 
out in detail. 
Since it was obviously not possible to examine more than a few 
feathers of each bird studied, similar feathers, as far as possible, 
were studied in each group taken up, namely, both inner and outer 
vane of a typical remex (i. e., not a highly specialized outer pri- 
mary or a weakened inner secondary), a back feather, and a breast 
feather, though in many eases the latter two were so similar that 
they did not merit separate descriptions. In other words, the method 
of study of groups has been: (1) a detailed study of represen- 
tative feathers of a type, and (2) a study of a number of other 
selected species, to determine the constancy or modifiability of the 
characters observed in the type, and to discover the presence or 
absence of further or different modifications. A discussion of the 
relationships suggested by feather morphology, and a review and 
summary of the epiphyology is given at the end of the section deal- 
ing with each group especially treated. 
I. Ratrrar 
Although there has been some doubt concerning the natural asso- 
ciation of all the so-called ratite birds into a single group, as far 
as feather structure is concerned, this grouping seems to be en- 
tirely permissible, providing the Crypturiformes, which Knowlton 
placed with them, be removed. The following characters are com- 
mon to the entire group, and as far as we know are not present, 
except as noted, in the adults of any other birds: (1) plumage uni- 
form, not segregated into pterylae (found only in Sphenisciformes 
and Palamedeae among carinate birds) ; (2) total absence of differ- 
entiated plumules and filoplumes; as far as known, both these types 
of feathers are never missing simultaneously in other birds; (3) en- 
tire absence of true pennaceous structure in any of the feathers, 
