494 PASSERIFORMES chap. 



D. Oscines. 



Of this group, or the true singing birds, the anatomy is even 

 less worked out than that of the Sithoscines, and consequently 

 the relationships are in many cases extremely doubtful. The 

 Hirundinidae stand distinctly apart, with no other Families 

 near them, though some similarity of habits, and possibly of 

 structure, may be recognised in certain Muscicapidae (especially 

 if Artamus be included among them), and to a less extent in 

 a few Stiirnidae ; yet almost as much resemblance may be 

 perceived in some Tyrannidae, which (not being Oscinine) can 

 have no affinity to the Hirundinidae. The likeness is therefore 

 probably one of analogy only, and, if so, of no taxonomic value. 

 Here again it must be stated that the Oscines hardly attain more 

 than the rank of a Family, and that in the Passeriformes the 

 " Families " have not the same value as in the foregoing Orders. 



The Alaudidae are generally recognisable by the casing of 

 their metatarsi (p. 496), but in other respects they seem to shew an 

 affinity to the Motacillidae {Ayithinae) on the one hand, and to 

 the Fringillidae on the other. The wing-characters, on which 

 reliance was formerly placed, prove to be wholly untrustworthy. 



As to the rest of the " Families " of Oscines, it is impossible 

 to indicate their probable relations by placing them in sequence, 

 or even at present to group more than a few of them with any 

 degree of assurance. Some have not yet been defined at all, and 

 few of them sufficiently for anyone to be confident as to their 

 limits. Thus in the Muscicctpidcie hardly any two systematic 

 ornithologists will agree as to which genera should be included 

 and which excluded. If restricted to Old World forms, there is 

 still no defined boundary between them and the GamjpeiAagidae, 

 while there is perhaps even less distinction between them and 

 the Sylviidae (or Sylviinae, if these last be included among the 

 Turdidae). Moreover, by some taxonoraers the Mniotiltidae have 

 been referred to the Muscicapidcte, and though there is an obvious 

 distinction between them in the number of the primaries, the 

 instance of the Alaudidae (already mentioned) shews that this 

 may be of very slight importance. 



Some other " Families " may perhaps be grouped with less 

 risk of error. The Troylodytidae, Certhiidae, Sittidac and 

 Paridae are possibly such ; but the limits of the last-named are 



