PASSEHES. 237 



PASSERES. 



Bill nearly straight in the gape. In some cases, there is 

 a slight hook at the end. No cere. Eyes lateral. The 

 character, indeed, of this extensive group, is purely of a 

 negative kind, comprehending all those birds which do not 

 possess the positive characters on which the other tribes are 

 founded. 



I. The first joint of the outer and middle toes connected 

 by a membrane. In some cases, this membrane extends to 

 the second joint. 



(A.) Gape remarkably large. Fissirostres. Bill short, 

 depressed, and slightly hooked. The species are all insec- 

 tivorous. This group is the best characterized of all the 

 Passeres *. 



Upper mandible, with a notch at the extremity. 



54. PROCNIAS. This genus includes the Ampelis ca- 

 runculata of GMELIN, and the Hirundo viridis of TEM- 

 MINCK, two species which appear to be the types of genera, 

 the carunculated throat of the former being remarkable. 



End of the bill entire. 



Nostrils open. Feathers closely set. Wings very long, 

 and flight rapid. 



55. CYPSELUS. Swift. Hind-toe directed forwards. 

 The three others, with only three phalanges. Hirundo 

 apus. 



56. HIRUNDO. Swallow. Toes of the common form. 

 The nests of those species which are the summer visitants 



If, by inserting the Fissirostres here, I have separated the Dentirostres 

 from the Accipitres, with which they have sever.il relations, I have brought 

 them nearer to the Conirostres, with which they are equally connected, and 

 have united the Procnias with its congeners. 



