Systematic Position of the Sheath-bills. 123 



('Auk/ vol. X. No. 2, April 1893), cites a number of 

 authors'^ who have taken up the story. Among these 

 may be mentioned Eyton, Cunningliam, Alfred Newton, 

 Kidder & Coues, Sclater & Salvia, Garrod, W. K. Parker, 

 Reichenow, Forbes, Gray, Sundevall, Wallace, Filrbringer, 

 and others ; while, finally, he himself published an illustrated 

 memoir " upon this remarkable type " in the ' Journal of 

 Anatomy and Physiology ' (London) in July 1891. 



It is not my intention to review the various opinions 

 expressed by this last formidable group of authorities, for 

 Shufeldt has already done so in his paper on the subject ; 

 but to anyone studying them it must be obvious that any 

 facts, however trifling and modest, Avhich may serve to 

 throw light on the life-history, morphology, and affinities 

 of a remarkable family are acceptable ; and this must be 

 taken as my excuse for the following notes. 



Remarkable and anomalous as the Sheath-bills are in 

 more ways than one, it is not so much that we are interested 

 in them, as in their relations to neighbouring groups and in 

 the part they may, or may not play in demonstrating the 

 processes of evolution whereby the Skuas, Gulls, Terns, 

 and Auks became differentiated from the main Pluvialine or 

 Jjimicoline stock. 



Did, for instance, these processes of evolution eventuate 

 through continuous or discontinuous variations? Were the 

 various Charadriiform groups or families originally insti- 

 tuted solely through saltations occurring in the germ plasm, 

 or to what extent have environmental or functional stresses 

 been responsible? 



I. Geographical Distribution. 

 As is well known, the present-day distribution of the 

 Chionididse is ultra-southern. There is no evidence derived 

 from fossil remains pointing to the fact that in past ages 

 the group had a more northerly distribution. On this 

 point there is a most complete palaeontological blank. The 



* Shufeldt gives references to all these papers in tlie publication just 

 quoted. 



