178 PROCEEDINGS OF THE ACADEMY OF [April, 



this is often one of the very best and most appreciable distinctions 

 between both species and subspecies. 



One of the most sm-prising as well as interesting developments of 

 our study has been the discovery of so many undescribed members of 

 the genus, among which two entirely distinct species with wholly 

 brownish lores like Collocalia leucophaea seem especially notable, as 

 does also one from New Caledonia allied to Collocalia leucopygia. 

 Most of the new forms are here elaborated from material recently col- 

 lected, and upon which no published report has yet been made. 



Much confusion has hitherto arisen because of failure properly to 

 discriminate those birds which have the tarsus more or less feathered 

 from those in which it is entirely bare. In some cases forms with 

 feathered and others with unfeathered tarsi have been considered sub- 

 specifically related or even identical ! The difficulty vanishes, however, 

 if all the birds with any feathering on the tarsus be considered apart 

 from the rest and placed, as they apparently should be, and as they are 

 in the following pages, in a separate subgeneric group. Indeed, it may 

 be best to regard them as even generically distinct, though it is not 

 here so done, because this character of tarsal feathering is the sole one 

 separating the groups, and while very marked in such forms as Col- 

 localia innominata, it is but slight, sometimes difficult to appreciate, 

 therefore in a sense intermediate, in Collocalia fuciphaga and its allies ; 

 and because if there be any logical difference between a genus and a 

 subgenus, the criterion of practical intergradation of characters through 

 intermediate species should be so considered. 



The proper generic name for the whole group seems to be Collocalia 

 — the one of current usage. The name Salangana St.-Hilaire has been 

 recently substituted ^ because supposedly of earlier date, but Salangana 

 now proves first to have been employed simply in a vernacular sense,^ 

 and to be citable as a generic term only from a later article ^ which is 

 posterior to the work containing Collocalia Gray.^ There are no other 

 synonyms. 



The material used in the preparation of the present memoir aggre- 

 gates 159 specimens, principally of recent collection, and represents 

 very nearly all the recognized forms. It is in large part that of the 

 United States National Museum, which is now, through the many 

 donations from Dr. W. L. Abbott, of considerable extent and includes 

 good series of many of the species. This has been supplemented by 



2 Richmond, Proc. U. S. Nat. Mus., XXV, 1902, p. 301. 

 ^ " Salanganes, " Saint-Hilaire, I' Echo du Monde Savant, IV, 1837, p. 84. 

 *Rev. Zool, 1840, p. 145. 

 List Gen. Birds, 1840, p. 8. 



