284 University of California Publications in Zoology fVoi.. 13 



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 cases 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. Ratitab 



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. 



