68 PROCEEDINGS OF THE ACADEMY OF 



The Mazatlan and Guadalaxara skins are the two bis^est 

 Myiarchi I ever saw ; one of them is marked "length (fresh) 9^;" 

 their bills are enormous, comparing with ordinary crinitus almost 

 as Tyrannus magnirostris or crassirostris do with carolinensis. 

 The}' are scarcely different from crinitus in color, except in the 

 definite fuscous stripe, about tj the width of the inner web, on 

 the tail feathers. The several Tehuantepec skins are essentially 

 similar, but grade towards crinitus, or rather towards irritabilis, 

 and in other skins the boundary line is too shadowy to be seen 

 at all. 



Of ni}- own knowledge, of course I have no idea what the 

 " Tyrannula mexicana" of Kaup is for no one who has not seen 

 the type can tell anything about it. But, according to Mr. Law- 

 rence (/. c), Dr. Selater has recently examined the type, and 

 announces it is what Prof. Baird called "cooperi" in 1858. Now 

 I have in my hand the specimen (No. 9100, Mus. S. I., "Mexique," 

 Verreaux) that furnished the account in the Birds of North 

 America, and it is one of the large heavy-billed examples of true 

 var. cooperi as characterized in this paper ; that is to sa}', " mexi- 

 canus" Kaup, and "cooperi" Kaup, are one and the same thing, 

 if Dr. Selater has correctby apprehended Prof. Baird's article. I 

 hardly see, however, how this can be, for Kaup must have meant 

 to indicate two species or varieties, and it is reasonable to suppose 

 his specimens showed some differences. My own surmise is, that 

 the t} r pe of " mexicanus" is one of those intermediate specimens 

 that Dr. Selater could hardly help identifying with Baird's de- 

 scription of "cooperi," the latter's No. 9100 being by no means 

 one of the largest-billed specimens ; and it seems to be also Mr. 

 Ridgway's opinion, to judge by his labelling, that " mexicanus" is 

 rather referable to the smaller-billed variety above characterized 

 under the name of irritabilis. However, the game is not worth 

 the candle, since fortunateby it proves that the name need not be 

 used at nil; and the sooner "mexicanus" is forgotten the better. 

 It has caused vexatious mistakes enough already, four different 

 authors having used it in as many different senses, in tire vain 

 attempt to identify something not identifiable. 



Turning to a more inviting point, it is interesting to observe 

 how many Myiarchi come to a focus, as it were, on and near the 

 Isthmus, and thence radiate in all directions. First we have in 

 winter the birds that breed in the United States, constituting true 



[July 2, 



