82 eidgway’s catalogue of noeth ameeican bieds. 
378a. Colaptes Auratus Mexicanus, (The western form.) 
378ft. Colaptes Auratus Hybridus. (This form is a true 
Hybrid, produced from the other two, and occurs 
in the upper Missouri.) 
The student, on reading these three names, sees at once the 
analogy between the three forms, and learns besides something 
of their history, which treating each by a different specific 
name would not have given him. 
Another advantage of the trinomial system is to designate the 
American form of a well-known old world species ; for instance, 
the “ American Barn Owl " is distinguished from the universally 
known European form (“ Aluco Flammeus ” as “ Aluco Flammeus 
Americanus," instead of the distinct specific name of “ Strix 
Pratincola ” in Baird’s list. 
There are no less than 160 forms subordinated by the use of 
trinomials in the present catalogue ! 
In conclusion, I would recommend our ornithologists carefully 
to note the truly scientific methods and the thoroughness of work 
indicated by this catalogue. 
There is one thing I should like to have seen added, and 
that is the habitat and geographical range of each species, as in 
Baird’s Catalogue of 1858 ; but this of course would have greatly 
extended the size of the book. 
Geographical distribution, and the migration, or rather 
oscillation, of species between their northern and their southern 
limits is a subject which we English ornithologists cannot study 
with the same facility as our North American brethren; their 
enormous territory, the boundaries of which (as in the present 
catalogue) extend from the North Pole to the Mexican Gulf, 
presents them with a magnificent field of observation, and a 
large majority of the species indicated as North American, 
actually rear their young (the true claim to being considered 
natives) in some portion or other of the territories. 
