I40 SHUFELDT. [Vol. XVII. 



alisphenoids) hide those structures upon the os squamosum of 

 either side, when the skull is looked at from in front. 



The supraoccipital {squama occipiiis) possesses an exceedingly 

 small, round supraoccipital foramen (the diameter being about 

 I mm.). 



The pterygoid bones are narrow both anteriorly and posteri- 

 orly, while their upper and lower margins are sharp. 



Their facets for the palatines are triangular in outline. 



The palatine bones are of about medium width ; the pars 

 plana, upon either side of the mesethmoid, long and strong, 

 and, when viewed from beneath, are seen to extend laterally 

 well out beyond the external borders of the palatines. 



Vomer rudimentary, or else unossified (that is, in all the 

 five specimens examined up to the present time, all of which 

 are probably subadult individuals). In older or adult birds, 

 ossification, to some slight extent, may take place. Mesially, 

 the maxillo-palatines are not widely separated. 



4. Bubo ignavus (Forst., 18 17). 



(See Fig. 3.) 



The auricular openings, which are without flaps, slightly asymmetrical ; 

 the cranium is symmetrical. 



The dermal parts of the auricular openings are rather large 

 and subequal in size, inasmuch as the right one is somewhat 

 larger than the left. They are oval in outline ; a male speci- 

 men (collected at Western Aker, Sept. 23, 1875) has its right 

 ear-opening measuring 30 mm. in height, and with a width of 

 19 mm., the left aperture possessing a height of 26 mm. and 

 a width of 16 mm. There are no ear-flaps, but the anterior 

 border upon either side develops a slightly elevated fold of 

 skin. 



The nostrils are subcircular in outline, and, as in the genus 

 Nyciea, situated rather superiorly. The cranium, which in all 

 its main characters agrees with the cranium in Nyctea scan- 

 diaca, is large and coarsely constructed, being symmetrical, and 

 with comparatively large orbital cavities ; posterior to which 

 latter we find the greatest height of the cranium to be situated. 



