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Show 1876.] MR. H. SAUNDERS ON THE STERNINA. 639 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 abnormal appearance to their pattern, it is not necessary to say anything 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, Hydrochelidon, Nania, 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. anas-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 characters (which is not the case), there exists a far more important difference between the foot in S. fuliginosa and in that of S. anas-theta, than there is between S. fuliginosa and any typical Sterna, such as S. fluviatilis. It would strike any one 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 inconsistent to separate them from true Sterna. It is, however, unnecessary 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 repetitions 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 discrepancies 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 Phatusa, which I put back under Sterna; whilst Nania, which he puts with Anous, I consider valid; several species also which he assigned to Hydrochelidon are now restored to Sterna. Of the discarded genera even the best seem to be based upon the size and shape 42* |