4 Henshaw on the Sjjecies of the Genus Passerella. 



more than one having strongly hinted at the probable specific iden- 

 tity of the four, while the methods in which they have been com- 

 bined have been nearly as various as the number of authors who 

 have had occasion to notice them. 



While the very close relationship existing between the two more 

 recently discovered forms (schistacea and megarhyncha) has usually 

 been recognized, from the occurrence of intermediate or doubtful 

 specimens, the tendency has been strong to keep separate the two 

 earlier described birds, mainly because no specimens with clearly 

 intermediate characteristics have been recognized. Having had the 

 very unusual opportunity of studying in the field the four forms in 

 question, as well as of examining a very large series of specimens in 

 the Smithsonian collection, many of which were collected by myself 

 in connection with the United States Geographical Surveys west 

 of the 100th Meridian, the conclusion seems to me to be unavoid- 

 able that the four forms are but modifications of a single species, 

 brought about through the agency of the laws of Geographical 

 Variation. 



Considering first in their relations to each other the P. schistacea 

 and P. megarhyncha, the first from the northern interior region, 

 the latter from the Southern Sierras, we find that, though very 

 distinct from each other when extreme samples of either form are 

 selected, they yet in the full series before me grade directly to- 

 gether, both in color and general size. Taking examples of mega- 

 rhyncha from the southern Coast Range of California, which may 

 be considered as the true home of the variety, that is, where its 

 peculiarities attain their greatest development, we find them in 

 their enormously developed bills and excessively lengthened tails, 

 as well as darkened colors, to present such a totally different 

 aspect that to liken them to schistacea seems almost absurd. 

 Changing, however, our point of observation to the eastern slope 

 of the Sierras, about Lake Tahoe, which is a region approaching 

 somewhat closely the home of schistacea, we find that the Passe- 

 rellas, though readily referable to megarhyncha, present very ap- 

 preciable difterences from those from the region just noted, and 

 furthermore, that the vai'iation is directly tow^ards the schistacea 

 type. The bills in specimens from the eastern slope are invariably 

 and very decidedly smaller than in examples from Fort Tejon and 

 that vicinity, though still much thickened when compared with 

 specimens from the interior (schistacea). The color of the under 



