FALCONIDAE. 

 III. THE UPPER MEMBRANE. 



A thin, glutinous layer of mucus. 



1. Bearing spots: Accipiter, Butco, Pernis, Falco and Cerchneis. 



2. Spotted variably: Circus cyaneus. 



3. Unspotted as a rule: Circus pygargus, aeruginosus and Astur. 



Dr. Hartert who classified the /^a/co«/dae according to the yellow 

 or green colour of the eggshell, in so doing opposed the character 

 of a certain layer of the shell of one of the genera to that of a 

 different layer of the other genera; namely, layer 11 of Falco and 

 Cerchneis which is only pigmented extremely superficially by oor- 

 hodein, to layer 1 of the Accipitrinae, Buteo and Pernis, which is 

 combined with oocyanin and is consequently coloured green. Dr. 

 Baldamus, in his criticism ') of Des Murs, speaking of the „gelb- 

 rotlichweisse Farbung der Schalenmasse" in the case of the true 

 Falcons, therefore judged of the colour of the shell as a whole 

 according to the thin covering of pigment which is only spread 

 over the surface of layer II (namely, of this layer solely); whilst 

 the Oologist des Murs, in calling the eggshell oi a\\ Rapaces diurni 

 a delicate bluish -) white, therefore judges of the eggshell as a 

 whole according to layer II after the removal (namely in the case 

 of Pernis, Falco and Cerc/j/je/s^ of the aforesaid covering of oorhodein. 

 The above would appear to me to be incorrect. 



The data which 1 have obtained and which are given in the 



') Journal fur Ornithologie, 1860 (pages 359 ef scq.). 



') Traits general d'OoIogie ornithologique au point de vue de la classifi- 

 cation, p. 205. 



I have never seen tliis bluish colour in layer II of eggshells of the genera 

 Falco or Cerchneis; I have seen it in the other genera, where it (namely, if 

 this layer is not particularly thick, which is sometimes the case) is caused by 

 the oocyanin of layer I showing through. 



