/ 



58 ' THE COLUMBID.E. 



truly Gallinaceous) are also monogamous. — Again, he says, — " No doubt there 

 is some similarity in the sterna, but it is confined to the posterior angles, and 

 consists in there being two notches in each." Now I deny that there is any thing 

 that can be fairly called similarity between the sterna ; the Gallinaceous birds 

 have two deep notches or emarginations extending from the posterior edge of the 

 sternum more than two-thirds of its length. But few of the Columbidce have two 

 notches, and where that is the case, the external one extends little more than 

 half the length of the sternum, and the internal one not more than the eighth 

 part of its length ; but in most of the Columbidae two small holes or foramina 

 supply the place of the internal notches. 



I think that each family ought to possess several distinct points of resemblance, 

 in habits of life, functions, external appearance, and internal structure, with 

 every other family of the same group, or at least with the typical genera of that 

 group, which no other group of birds possesses in common with them ; that each 

 genus should consist of birds similar in their general habits, appearance, and 

 structure, but constantly differing from each other in some one character ; and 

 that this constant difference in some one particular constitutes a species. When 

 there is no general resemblance through the whole of the families, but only 

 a similarity in a few particulars between some of the extreme species of each 

 family, they ought not to be included in the same order, this connection 

 between the extremes of the different families, clearly pointing out that they 

 should be considered as distinct consecutive orders. 



I will now enumerate the points of difference and agreement between what I 

 consider the true Gallinaceous birds («, e. the Pavonidae, Tetraonidae, and Cracidce 

 of Selby) and the Columbidae.' 



In my comparison between the Columbidae and Rasores, I do not include 

 Selby's Geophilus. This genus is little known. It appears to bear a much 

 nearer resemblance to the Rasores than any other of the Pigeon family, particu- 

 larly as regards the number of eggs ; the young being able to see at birth ; being 

 hatched on the ground, and running as soon as hatched ; but I think all these 

 points of resemblance afford no reason why all the Pigeons should be classed with 

 the Rasores ; but that they only prove a connecting link to exist between them. 



Pigeons — with the exception of the Rock Pigeon — build their nests in trees. 

 The Rasores — with the exception of sonrc species of Cracidae — uniformly make 

 their nests on the ground. 



Pigeons never lay more than two eggs. — The Gallinaceous birds always lay 

 more than two. 



Pigeons are blind at birth, and remain so several days. — The Gallinaceous birds 

 eee at birth. 



Pigeons remain several weeks in the nest after they are hatched, and until 



