No. I.] THE CRANIUM IN THE OWLS. 159 



and have the appearance of being almost quite symmetrical. 

 Thus, their orbital portions do not seem to offer any difference 

 upon the two sides, as both descend about an equal distance 

 upon either posterior orbital wall ; on the other hand, the lat- 

 eral portion on the right side, where it articulates with the 

 anteriormost apex of the parietal bone, and the here abnor- 

 mally developed and much uptilted crest of the os squamosum, 

 is more elevated than on the left side. Otherwise the differ- 

 ence is very slight. 



The osseous crests on the os squamosum, where the asym- 

 metry is most evident, are, upon the whole, so abnormally 

 large, deep, and conspicuously outstanding, that they, almost 

 in their entirety, can be seen beyond the orbits, if the cranium 

 be viewed from in front. As in the genus Asio, they are not 

 distinguished from any of the bones with which they articulate 

 above by any distinct groove or depression, but enter into the 

 uninterrupted lateral contour of the cranium, where it is seen 

 from in front. Both sides are distorted, the left side being the 

 more so. On the right side, the osseous crest is extended up- 

 wards to a height quite coequal with that of the superior border 

 of the orbit, but it abruptly terminates here, as it comes in con- 

 tact with the frontal, at a considerable distance (7.2 mm.) pos- 

 terior to the orbit, and in this manner crowding far backwards 

 the apex of the parietal bone. In the middle the osseous crest 

 is produced in such a way as to form an anterio-inferiorly 

 directed and rounded process, which with its point impinges 

 upon the hinder border of the orbital crest of the os alisphe- 

 noides. The combined heights of the osseous crests upon this 

 side are equal to 20 mm. On the left side the osseous crest 

 is abnormally vertically compressed ; it commences at a point 

 above, at about opposite the middle of the orbit, and close to 

 the latter's hinder border, thus being farther forward anteri- 

 orly than it is upon the right side, as the crest is here sup- 

 ported by the superior extremity of the orbital crest upon os 

 alisphe7ioides. Here also, from a point a little below its middle, 

 the crest is produced in a long, inferiorly directed process ; but 

 its apex is found as low down as the mandible, where, with a 

 feeble, yet with an easily distinguished articulatory facet, it 



