684 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



is found in the same places as the very small and darker colored 

 0. cassini, the former extending across the range of 0. Tiastatus, or at 

 least apparently separating the ranges of the two forms of that 

 species ia Oaxaca, though the range of 0. Tiastatus may prove to be 

 not interrupted, but contiauous from Sinaloa to Yucatan. Like- 

 wise, in northern and central Mexico, we have ia the same or closely 

 contiguous localities, 0. triehopsis, 0. finosus, 0. vinaceus, and a 

 form of 0. asio, representing the bristly-toed group. 



It should be emphasized that very much more material from dif- 

 ferent parts of Mexico- and Central America is needed before a really 

 correct understanding of the status and relationships of the several 

 forms can be obtained. 



KEY TO THE SPECIES AND SUBSPECIES OF OTUS.'J 



a. General color of upper parts mottled or vermiculated grayish or brownisji. 

 6. Toes bristled, 

 c. Basal portion of toes feathered or densely bristled, the feathering of lower 

 portion of tarsus not ending abruptly. 

 d. Outer webs of exterior row of scapulars mostly white, not broken by mot- 

 tling, vermiculations, or bars; ■srhitish spots on proximal half of longer pri- 

 maries nearly to quite as broad as (sometimes broader than) the darker 

 interspaces ; legs, if not immaculate, coarsely mottled or barred. 

 e. Middle toe, measured from angle between middle and outer toes, not leas 

 than 15 mm.; bristly tips to feathers of face slightly developed; color- 

 ation of occiput and lower hindneck practically uniform with that of 

 crown and back; black streaks on upper and under parts relatively nar- 

 rower. {Oius asio.) 

 f. Eastern forms, conspicuously dichromatic (a grayish and a clear cinna- 

 mon-rufous phase). 

 g. Darker, with under parts more thickly penciled. 

 h. Smaller (wing averaging less than 145 in male, leas than 152 in 

 female). (Lower Austral Zone, west to northeastern Texas.) 



Otus asio asio (p. 687). 



hh. Larger (wing averaging more than 160 in male, more than 165 in 



female). 



i. Paler and smaller (wing averaging 160.2 in male); imder parts 



less heavily penciled. (Upper Austral and Transition zones, 



east of the Great Plains.) Otus asio nsevius (p. 690). 



ii. Darker and lai^er (wing averaging 164.2 in male); under parts 

 more heavily penciled. (Northeast-central Texas.) 



Otus asio hasbroucki (p. 694). 

 gg. Paler, with under parts more openly penciled. (Lower Bio Grande 

 Valley of Texas and northeastern Mexico.) 



Otas asio mccallii (p. 693). 

 ff. Western forms, not conspicuously, if at all, dichromatic (no rufous 

 phase). 

 g. Larger (wing averaging 160 or more in male, more than 166 in female); 

 vermiculations coarser and less dense, both above and below. 

 h. Wing averaging less than 162 in males, less than 172 in females. 



a One species, 0. pinoms Nelson, is not included in the key, the only known speci- 

 men being a young bird. 



