1876.] MR. H. SAUNDERS ON THE STERNIN.E. f)33 



first and second weeks in October. At this season, too, the grey tint 

 on the rump and tail-coverts which is also assumed by some species is 

 apt to lead to confusion. Of the difficulties presented by the wear- 

 ing-away of the grey frosty surface on the primaries, giving an ab- 

 normal appearance to their pattern, it is not necessary to say any- 

 thing beyond drawing attention to their existence. 



After careful examination of the representatives of all the genera 

 into which this subfamily has been divided, I am unable to discover 

 any satisfactory reasons for the adoption of more than five, viz. 

 Sterna, Flydrochelidon, Ncenia, Gygis, and Anous. It is true that 

 in many forms there appears to be considerable departure from what 

 we have been accustomed to consider typical Sterna ; and this was 

 especially evident to those systematists who treated principally of 

 European or North-American species ; but when the various species 

 of the whole world are examined, so many connecting links and gra- 

 dations will be found to exist, as to reduce the structural distinctions 

 to a minimum, and to preclude the possibility of adopting with any 

 degree of consistency several genera which at first glance seemed 

 valid enough. For example, the Sooty Terns (S. fuliginosa, S. ances- 

 theta, and S. lunata) have had no less than three genera erected for 

 one of their number by Wagler alone, viz. Onychoprion, Haliplana, 

 and Planetis, the definitions of which will hardly bear analysis ; but 

 even if any one of them were based upon genuine structural cha- 

 racters (which is not the case), there exists a far more important 

 difference between the foot in S. fuliginosa and in that of S. ances- 

 theta, than there is between S. fuliginosa and any typical Sterna, 

 such as S. fluviatilis. It would strike anyone as absurd to separate 

 these two Sooty Terns generically, seeing that their resemblance is so 

 close that for some time even their specific characteristics were by 

 no means well known ; yet, unless this is done, it is fully as incon- 

 sistent to separate them from true Sterna. It is, however, unneces- 

 sary to say more upon this particular subject, as it will be noticed 

 when treating of the species in question. The result of the mania 

 which at one time prevailed for the manufacture of genera may be 

 seen in the fact that whereas the members of the subfamily Sterninae 

 are about 50 in number, the genera erected for their reception are 

 upwards of 30. It is true that many of these are merely vain repe- 

 titions of previously existing genera, the names of which did not 

 happen to suit the fancy of the respective systematists, and that by 

 discarding these synonyms the burden might be endured if the dis- 

 crepancies of opinion as to the genera in which the various species 

 should be located were not hopelessly irreconcilable, a single species 

 being sometimes assigned to 7 or 8 different genera. Dismissing all 

 but those which are based upon structural characters, independent 

 investigations have led me to adopt substantially the genera accepted 

 by the late G. R. Gray (Gen. Birds iii. p. 658), with the exception 

 of Phcetusa, which I put back under Sterna ; whilst Ncenia, which 

 he puts with Anous, I consider valid ; several species also which he 

 assigned to Hi/drochelidon are now restored to Sterna. Of the dis- 

 carded genera even the best seem to be based upon the size and shape 



[3] 



