that connect the Orders and Families of Birds. 493 



body, which is compressed and flattened on the sides, in conse- 

 quence, as M. Cuvier has informed us, of the narrowness of their 

 sternum. Were we here allowed to draw an inference from the 

 analogical construction of other bodies, which move with the 

 greater facility through the water in proportion as they assume 

 this compressed and keel-like form, we might almost conclude 

 that this structure, peculiar to the birds of the present family, 

 facilitates their progress through that element*, and is intended 

 to counterbalance the deficiency in the formation of the foot, 

 which separates them from the truer and more perfectly formed 

 Water-birds. It is certain that the greater portion of these birds 

 are excellent swimmers ; and in such habits, as well as in the 

 shortness of their tarsi, which is equally conducive to their 

 powers in swimming, they are found to deviate from all the 

 remaining groups of the order. They thus become an aberrant 

 family, and lead directly, as has been before noticed, to the suc- 

 ceeding order of Natatores. The genus Parra, Linn., distin- 

 guished from Rallus, Linn, by the greater length of the toes, 

 and more particularly by the length and straightness of the nails, 

 is yet allied to that genus by the general structure of the bill. 

 With Parra may be allied Palamedea, Linn., and Chauna, 111., 

 the Parra chavaria of the "Si/ste/na Natura," both of which seem 

 to approach Parra in affinity, although the latter of them is so 

 imperfectly known that its situation cannot be decided with cer- 

 tainty. To Rallus succeeds Cre.r, Bechst., which by its stronger 

 and shorter bill seems to lead on to Gallinula, Briss., from which 

 genus, although agreeing with it in general appearance, it is de- 

 cidedly separated by its terrestrial habits. Gallinula is set apart 

 from the foregoing groups by the greater length of the toes, and 

 the dilatation of the upper mandible upon the forehead. This 



* Mr. Wilson, speaking of tiie Rallus Firginianus, mentions this character as condu- 

 cive to the progress of the bird through the reedy marshes. Jm. Orn. vol. vi. p. 33. 

 , ; , , J 3 s 2 latter 



